Reducing nonradiative recombination in perovskite solar cells with a porous insulator contact

Mercapto-functionalized scaffold improves perovskite buried interfaces for tandem photovoltaics

Tandem photovoltaics hold great potential to surpass the efficiency limit of single-junction solar cells. Detrimental structural defects and chemical reactions at buried interfaces of subcells considerably impede the performance of integrated tandems. Here, we devise a mercapto-functionalized mesoporous silica layer as a superstructure at the buried interface to modulate the crystallisation, eliminate nanovoids, passivate defects, and suppress the oxidation of Sn(II) in the tin-lead perovskite films, contributing substantially to reduce charge carrier losses and improve stability in positive-intrinsic-negative structured devices. Consequently, the tin-lead perovskite single-junction cells show efficiency values of up to 23.7% with the best open-circuit voltage of 0.89 V. With the enhanced subcells, our double-junction tandems show efficiency values of 29.6% (certified 29.5% and steady-state 28.7%) and 24.7% on solar cells and 11.3 cm2 mini-modules, respectively. Encapsulated tandems maintain 90% of initial efficiency after 445 h of maximum power point tracking under simulated 1-sun illumination.

Metalized Porphyrin-Based COFs for Conductive Porous Layers in Perovskite Solar Cells to Enhance Electron Injection, Defect Passivation, and Lead-Protection

In perovskite solar cells (PSCs), the introduction of an intermediate layer to bridge the transport and photoactive layers has become a key strategy for enhancing carrier extraction efficiency. However, traditional approaches are often limited by the seesaw effect, making it challenging to achieve an optimal balance between electron transport and defect passivation. In this study, we employed a Cu2+-loaded metalized porphyrin-based covalent organic framework (Cu-Por-COF) as a conductive porous layer (CPL) at the perovskite bottom interface. Experimental results showed that a Cu-Por-COF coverage of 19% significantly enhanced electron transport and effectively suppressed long-distance electron diffusion. Moreover, the carefully designed Cu-Por-COF provided abundant active sites, which improved the film-forming quality of the perovskite layer, thereby facilitating the beneficial synergy of electron injection and defect passivation. The n-i-p type devices achieved a power conversion efficiency (PCE) of 25.41% (0.09 cm2) and 21.99% (1.01 cm2). Using Cu-Por-COF to stabilize the perovskite crystal structure, the unencapsulated devices retained over 81% of its initial efficiency after 2000 h. Additionally, Cu-Por-COF effectively chelated lead ions and thus enhanced the environmental sustainability of PSCs.

Homogenized Self-Assembled Molecules for Inverted Perovskite Solar Cells

Inverted perovskite solar cells (PSCs) have rapidly improved, driven by advancements in self-assembled molecules (SAMs). However, achieving homogeneous SAM coverage on substrates remains challenging, directly impacting device performance and stability. Here, we present (4-(pyren-1-yl)phenyl)phosphonic acid (PhPAPy), a SAM with a rigid aromatic ring structure. Ab initio molecular dynamics (AIMD) simulations reveal that this rigidity limits rotational freedom, promoting a near-vertical molecular orientation on the substrate. Additionally, π-π interactions between the planar pyrene rings enhance molecular packing, forming a homogeneous and dense SAM layer. As a result, the uniform PhPAPy effectively minimizes perovskite-substrate direct contact, enhances the interfacial properties, reduces buried interface defects, and improves both efficiency and stability. With PhPAPy SAM, the assembled inverted PSCs achieve a certified reverse-scanning power conversion efficiency (PCE) of 26.74% and a certified stabilized power output (SPO) efficiency of 26.12% (from National Institute of Metrology in China). These devices retain 95% of their initial efficiency after 2000 h of maximum power point tracking (MPPT) under continuous AM 1.5G illumination at 65 °C and ambient humidity (ISOS-L-2).

Amidinium-Based 2D Spacer Cations Enhance Efficiency and High-Temperature Photostability of Perovskite Solar Cells

2D/3D perovskite heterojunctions represent a promising approach to enhance the efficiency and stability of perovskite solar cells (PSCs). However, the photostability at elevated temperatures of conventional 2D/3D heterostructures, employing ammonium-based spacer cations, is severely limited by deprotonation reactions, hindering their practical application. In this study, amidinium-based 2D spacer cations as an alternative, leveraging their higher acid dissociation constants, to mitigate deprotonation-induced instability while providing excellent defect passivation effect is introduced. Amidinium passivation not only facilitates formation of thermally stable 2D/3D heterostructures but also suppresses non-radiative recombination and enhances carrier transport dynamics. PSCs with amidinium-based bulk and surface passivation achieve a state-of-the-art power conversion efficiency of 26.52% for 2D/3D PSCs and exhibit outstanding high-temperature photostability, retaining 90.6% of initial efficiency after 1000 h of continuous illumination at maximum power point at 85 °C. This work offers valuable insights into designing high-performance, durable PSCs under challenging conditions.

Grains > 2 µm with Regulating Grain Boundaries for Efficient Wide-Bandgap Perovskite and All-Perovskite Tandem Solar Cells

Tandem perovskite solar cells represent a significant avenue for the future development of perovskite photovoltaics. Despite their promise, wide-bandgap perovskites, essential for constructing efficient tandem structures, have encountered formidable challenges. Notably, the high bromine content (>40%) in these 1.78 eV bandgap perovskites triggers rapid crystallization, complicating the control of grain boundary growth and leading to films with smaller grain sizes and higher defect density than those with narrower bandgaps. To address this, potassium tetrakis(pentafluorophenyl)borate molecules are incorporated into the antisolvent, employing a crystallographic orientation-tailored strategy to optimize grain boundary growth, thereby achieving wide-bandgap perovskite films with grains exceeding 2 µm and effectively eliminating surplus lead halide and defects at the grain boundaries. As a result, remarkable efficiency is achieved in single-junction wide-bandgap perovskite devices, with a power conversion efficiency (PCE) of 20.7%, and in all-perovskite tandem devices, with a two-terminal PCE of 28.3% and a four-terminal PCE of 29.1%, which all rank among the highest reported values in the literature. Moreover, the stability of these devices has been markedly improved. These findings offer a novel perspective for driving further advancements in the perovskite solar cell domain.

The Rise of Chalcohalide Solar Cells: Comprehensive Insights From Materials to Devices

While lead-halide perovskites achieve high efficiencies, their toxicity and instability drive the search for safer materials. Chalcohalides, combining chalcogen and halogen anions in versatile structures, emerge as earth-abundant, nontoxic alternatives for efficient photovoltaic (PV) devices. A wide variety of chalcohalide materials, including pnictogen metals-, post-transition metals-, mixed-metals- and organic-inorganic metals-based chalcohalides, offer diverse structural, compositional, and optoelectronic characteristics. Some of these materials have already been experimentally synthesized and integrated into PV devices, achieving efficiencies of 4-6%, while others remain theoretically predicated. Despite these advancements, significant challenges must be addressed to fully realize the potential of chalcohalides as next-generation PV absorbers. This review provides a comprehensive insight of the fundamental properties of chalcohalide materials, emphasizing their unique structures, highly interesting optoelectronic and dielectric properties, to fuel further research and guide the development of high-efficiency chalcohalide solar cells. Various synthesis techniques are discussed, highlighting important and potentially overlooked strategies for fabricating complex quaternary and pentanary chalcohalide materials. Additionally, the working principles of different device structures and recent advances in fabricating efficient chalcohalide solar cells are covered. We hope that this review inspires further exciting research, innovative approaches, and breakthroughs in the field of chalcohalide materials.

Optimizing Molecular Packing and Interfacial Contact via Halogenated N-Glycidyl Carbazole Small Molecules for Low Energy Loss and Highly Efficient Inverted Perovskite Solar Cells

Nonideal interfacial contact and non-radiative voltage loss in self-assembled monolayers (SAMs)-based inverted perovskite solar cells (PSCs) limit their further development. Herein, two carbazole-based molecules with different halogen atoms (X-OCZ, X = Cl or Br) are developed as efficient interfacial regulators. The halogen effect not only finely modulates the molecular packing, crystallinity, and surface contact potential of the MeO-2PACz analogue via self-induced intermolecular interactions but also significantly influences the subsequent crystal growth of perovskite, thus resulting in the formation of high-quality films with enhanced crystallinity, improved energy level alignment, and depressed non-radiative recombination. Importantly, the Cl-OCZ-mediated device exhibits a minimal interfacial carrier transport energy barrier of 0.10 eV and an impressive charge collection efficiency of 93.6%. Moreover, the target device (aperture area: 0.09 cm2) shows an exceptional efficiency of 26.57% (certified 26.4%) along with enhanced thermal and operational stability. The strategy is also extended to large area devices, delivering efficiencies of 25.0% for a 1 cm2 device and 22.9% for a 12.96 cm2 minimodule. This study highlights the halogen role of interfacial small molecules in optimizing molecular packing and interfacial contact toward highly efficient PSCs with minimized energy loss and non-radiative recombination.

On-demand formation of Lewis bases for efficient and stable perovskite solar cells

In the fabrication of FAPbI3-based perovskite solar cells, Lewis bases play a crucial role in facilitating the formation of the desired photovoltaic α-phase. However, an inherent contradiction exists in their role: they must strongly bind to stabilize the intermediate δ-phase, yet weakly bind for rapid removal to enable phase transition and grain growth. To resolve this conflict, we introduced an on-demand Lewis base molecule formation strategy. This approach utilized Lewis-acid-containing organic salts as synthesis additives, which deprotonated to generate Lewis bases precisely when needed and could be reprotonated back to salts for rapid removal once their role is fulfilled. This method promoted the optimal crystallization of α-phase FAPbI3 perovskite films, ensuring the uniform vertical distribution of A-site cations, larger grain sizes and fewer voids at buried interfaces. Perovskite solar cells incorporating semicarbazide hydrochloride achieved an efficiency of 26.1%, with a National Renewable Energy Laboratory-certified quasi-steady-state efficiency of 25.33%. These cells retained 96% of their initial efficiency after 1,000 h of operation at 85 °C under maximum power point tracking. Additionally, mini-modules with an aperture area of 11.52 cm2 reached an efficiency of 21.47%. This strategy is broadly applicable to all Lewis-acid-containing organic salts with low acid dissociation constants and offers a universal approach to enhance the performance of perovskite solar cells and modules.

Homogeneous 2D/3D heterostructured tin halide perovskite photovoltaics

Tin halide perovskites (THPs) have emerged as promising lead-free candidates for eco-friendly perovskite solar cells, but their photovoltaic performance still lags behind that of lead-based counterparts due to poor thin-film quality. Constructing two-dimensional/three-dimensional (2D/3D) heterostructures can effectively regulate crystallization and suppress defect formation for developing high-quality THP thin films. However, the high aggregation barrier prevents large 2D perovskite colloids from forming stable clusters, making 2D THPs nucleate more slowly than their 3D analogues. Such distinct nucleation kinetics cause undesirable 2D/3D phase segregation that compromises both photovoltaic performance and device durability. Here we introduce small inorganic caesium cations to partially replace bulky organic cations in the electrical double layers of 2D THP colloids, reducing the colloid size to lower their aggregation barrier. The reduced electrostatic repulsion promotes the coagulation of 2D and 3D THP colloids in the precursor solution, synchronizing their nucleation kinetics for the growth of 2D/3D heterostructured THP thin films with a homogeneous microstructure and markedly reduced trap states. Consequently, the caesium-incorporated THP solar cells deliver an excellent power conversion efficiency of 17.13% (certified 16.65%) and exhibit stable operation under continuous one-sun illumination for over 1,500 h in nitrogen without encapsulation. This study offers new insights into the colloidal chemistry and crystallization engineering of mixed-dimensional heterostructures, paving the way for high-performance lead-free perovskite photovoltaics.

Cost Effectivities Analysis of Perovskite Solar Cells: Will it Outperform Crystalline Silicon Ones?

The commercialization of perovskite solar cells (PSCs) has garnered worldwide attention and many efforts were devoted on the improvement of efficiency and stability. Here, we estimated the cost effectivities of PSCs based on the current industrial condition. Through the analysis of current process, the manufacturing cost and the levelized cost of electricity (LCOE) of PSCs is estimated as 0.57 $ W-1 and 18-22 US cents (kWh)-1, respectively, and we demonstrate the materials cost shares 70% of the total cost. Sensitivity analysis indicates that the improvement of efficiency, yield and decrease in materials cost significantly reduce the cost of the modules. Analysis of the module cost and LCOE indicates that the PSCs have the potential to outperform the silicon solar cells in the condition of over 25% efficiency and 25-year lifetime in future. To achieve this target, it is essential to further refine the fabrication processes of each layer in the module, develop stable inorganic transport materials, and precisely control material formation and processing at the microscale and nanoscale to enhance charge transport.

Achieving >23% Efficiency Perovskite Solar Minimodules with Surface Conductive Coordination Polymer

Despite the reported high efficiencies of small-area perovskite photovoltaic cells, the deficiency in large-area modules has impeded the commercialization of perovskite photovoltaics. Enhancing the surface/interface conductivity and carrier-transport in polycrystalline perovskite films presents significant potential for boosting the efficiency of perovskite solar modules (PSMs) by mitigating voltage losses. This is particularly critical for multi-series connected sub-cell modules, where device resistance significantly impacts performance compared to small-area cells. Here, an effective approach is reported for decreasing photovoltage loss through surface/interface modulation of perovskite film with a surface conductive coordination polymer. With post-treatment of meso-tetra pyridine porphyrin on perovskite film, PbI2 on perovskite film reacts with pyridine units in porphyrins to generate an iso-structural 2D coordination polymer with a layered surface conductivity as high as 1.14 × 102 S m-1, due to the effect of surface structure reconstruction. Modified perovskite film exhibits greatly increased surface/interface conductivity. The champion PSM obtains a record efficiency up to 23.39% (certified 22.63% with an aperture area of 11.42 cm2) featuring only 0.33-volt voltage loss. Such a modification also leads to substantially improved operational device stability.

Exploring the electronic properties of carbon nanoflake-based charge transport materials for perovskite solar cells: a computational study

Carbon-based materials, in particular carbon nanoflakes (CNFs) and carbon quantum dots (CQDs), have been increasingly used in charge transport layers and electrodes for perovskite solar cells (PSCs). There are practically limitless possibilities of designing such materials with different sizes, shapes and functional groups, which allow modulating their properties such as band alignment and charge transport. Solid state packing further modifies these properties. However, there is still limited insight into the electronic properties of these types of materials as a function of their chemical composition, structure, and packing. Here, we compute the dependence of band alignment and charge transport characteristics on the size, chemical composition, and structure of commonly accessible types of nanoflakes and functional groups and further consider the effect of their packing. We use a combination of density functional theory (DFT) and density functional-based tight binding (DFTB) to get electronic structure level insight at length scales (nanoflake sizes) relevant to the experiment. We find that CNFs must have sizes as small as 1.3 nm to provide band alignments suitable for their use as hole transport materials in PSCs containing the commonly used methylammonium lead iodide perovskite. We show that both shape and functionalization can significantly modify the band alignment of the CNF, by more than half an electron volt. Inter-flake interactions further modify the band alignment, in some cases by about half an electron volt. CNFs having small sizes possess sufficient inter-flake electronic coupling for efficient hole transport. In contrast, no shape or size of CNFs produces band alignment suitable for their use as electron transport materials.

Buried Interface Regulation with a Supramolecular Assembled Template Enables High-Performance Perovskite Solar Cells for Minimizing the VOC Deficit

Despite the rapid development of perovskite solar cells (PSCs) in the past decade, the open-circuit voltage (VOC) of PSCs still lags behind the theoretical Shockley-Queisser limit. Energy-level mismatch and unwanted nonradiative recombination at key interfaces are the main factors detrimental to VOC. Herein, a perovskite crystallization-driven template is constructed at the SnO2/perovskite buried interface through a self-assembled amphiphilic phosphonate derivative. The highly oriented supramolecular template grows from an evolutionary selection growth via solid-solid phase transition. This strategy induces perovskite crystallization into a highly preferred (100) orientation toward out-of-plane direction and facilitated carrier extraction and transfer due to the elimination of energy barrier. This self-assembly process positively passivates the intrinsic surface defects at the SnO2/perovskite interface through the functionalized moieties, a marked contrast to the passive effect achieved via incidental contacts in conventional passivation methods. As a result, PSCs with buried interface modification exhibit a promising PCE of 25.34%, with a maximum VOC of 1.23 V, corresponding to a mere 0.306 V deficit (for perovskite bandgap of 1.536 eV), reaching 97.2% of the theoretical VOC limit. This strategy spontaneously improves the long-term operational stability of PSCs under thermal and moisture stress (ISOS-L-3: MPP, 65 °C, 50% RH, T92 lifetime exceeding 1200 h).

Regulating three-layer full carbon electrodes to enhance the cell performance of CsPbI3 perovskite solar cells

Carbon-based perovskite solar cells exhibit a promising application prospect due to its cost effective and attractive hydrophobic nature and chemical inertness, but are still limited to unsatisfied device efficiency. Herein, we design a triple-layer full-carbon electrode for n-i-p typed perovskite solar cells, which is comprised of a modified macroporous carbon layer, a highly conductive graphite layer and a thin dense carbon layer, and each layer undertakes different contribution to improving the cell performance. Based on this full-carbon electrode, inorganic CsPbI3 perovskite solar cells exhibit >19% certified efficiency which is the highest result among carbon-based CsPbI3 devices. On one hand, carbon quantum dots decorated on the macro-porous carbon layer can realize better energy alignment of full-carbon electrode/spiro-OMeTAD/CsPbI3 interface, on the other hand, highly conductive graphite layer is advantageous to carrier transporting. Typically, the top dense carbon layer exhibits significant thermal radiation ability, which can reduce the operational temperature of devices by about 10 °C, both from theoretical simulation and experimental testing. Thereby, packaged full-carbon electrode based CsPbI3 cells exhibit much better photothermal stability at ~70°C accompanied by white light emitting diode illumination, which exhibit no efficiency degradation after 2000 h continuous operational tracking.

Recent Advances in Wide-Bandgap Perovskite Solar Cells

Wide-bandgap (WBG) perovskite solar cells (PSCs) have garnered considerable attention of late for their potential as semitransparent photovoltaics for building integration, top-cells in tandem configurations, and indoor photovoltaics (IPVs) for Internet of Things (IoT) applications. However, recent investigations have unveiled that underlying defect-mediated phase segregation, ion migration, lattice strain, and other factors can give rise to self-accelerated degradation reactions and the contraction of quasi-Fermi level splitting (QFLS) within devices. Extensive efforts have been undertaken to reduce defect densities in bulks, at surfaces, and across interfaces with charge transport layers (CTLs). This review provides a timely and comprehensive understanding of the intrinsic defect ecosystem in WBG perovskites, and mechanistically elucidates their impacts on device stability and open circuit voltage losses. Subsequently, recent advances in defect passivation strategies are cross-sectionally overviewed, covering various components of devices. The applications of WBG PSCs in semitransparent devices, tandem applications, and IPVs are discussed. Finally, prospects and challenges are proposed, providing insights for future research and technological advancements.

Enhanced Buried Interface Engineering for Efficient Inverted Perovskite Solar Cells Fabricated via Vapor-Solid Reaction

Vapor-deposited inverted perovskite solar cells utilizing self-assembled monolayer (SAM) as hole transport material have gained significant attention for their high efficiencies and compatibility with silicon/perovskite monolithic tandem devices. However, as a small molecule, the SAM layer suffers low thermal tolerance in comparison with other metal oxide or polymers, rendering poor efficiency in solar device with high-temperature (> 160 °C) fabricating procedures. In this study, a dual modification approach involving AlOx and F-doped phenyltrimethylammonium bromide (F-PTABr) layers is introduced to enhance the buried interface. The AlOx dielectric layer improves the interface contact and prevents the upward diffusion of SAM molecules during the vapor-solid reaction at 170 °C, while the F-PTABr layer regulates crystal growth and reduces the interfacial defects. As a result, the AlOx/F-PTABr-treated perovskite film exhibits a homogeneous, pinhole-free morphology with improved crystal quality compared to the control films. This leads to a champion power conversion efficiency of 21.53% for the inverted perovskite solar cells. Moreover, the encapsulated devices maintained 90% of the initial efficiency after 600 h of ageing at 85 °C in air, demonstrating promising potential for silicon/perovskite tandem application.

Mobile Oxygen Capture Enhances Photothermal Stability of Perovskite Solar Cells Under ISOS Protocols

Stability testing protocols from the International Summit on Organic and Hybrid Solar Cell Stability (ISOS) are essential for standardizing studies on the photothermally operational stability of perovskite solar cells (PSCs). Under photothermal conditions, the migration of oxygen from SnO2 layer induces cationic dehydrogenation at the A-site of the perovskite, accelerating degradation to PbI2. This leads to the formation of photoinduced I2 and Pb0 defects, significantly compromising long-term stability. In this study, ordonezite (ZnSb2O6-x) as a multifunctional electron transport layer (ETL) that captures migrating oxygen atoms at the SnO2/perovskite interface is introduced, effectively preventing degradation of the buried interface. Additionally, the lattice match between ZnSb2O6-x and perovskite facilitates well-ordered perovskite film growth. As a result, PSCs featuring ZnSb2O6-x ETLs achieved a high power conversion efficiency of 25.02% and retained 90.62% of their initial performance after 1000 h under the ISOS-D-2 protocol. Furthermore, devices demonstrated remarkable thermal stability, maintaining 83.69% of their original performance after 800 h of maximum power point tracking at 85 °C, meeting the stringent ISOS-L-2 protocol requirements.

Modulating competitive adsorption of hybrid self-assembled molecules for efficient wide-bandgap perovskite solar cells and tandems

The employment of self-assembled molecular hybrid could improve buried interface in perovskite solar cells (PSCs). However, the interplay among hybrid self-assembled monolayers (SAMs) during the deposition process has not been well-studied. Herein, we study the interaction between co-adsorbents and commonly used SAM material, [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) for wide-bandgap (WBG) PSCs. It is found that the co-adsorbent, 6-aminohexane-1-sulfonic acid (SA) tends to fill the uncovered sites without interference with Me-4PACz, ensuring the formation of a dense hole selective layer. Moreover, the use of SA/Me-4PACz mixed SAMs could effectively reduce the interfacial non-radiative recombination loss, optimize the energy alignment at the buried interface and regulate the crystallization of WBG perovskite. As a result, the 1.77 eV WBG PSCs deliver a power conversion efficiency (PCE) of 20.67% (20.21% certified) and an impressive open-circuit voltage (VOC) of 1.332 V (1.313 V certified). By combining with a 1.26 eV narrow-bandgap (NBG) PSC, we further fabricate 2-terminal all-perovskite tandem solar cells (TSCs) with a PCE of 28.94% (28.78% certified) for 0.087 cm2 and 23.92% for mini-module with an aperture area of 11.3 cm2.

Activated Corrosion and Recovery in Lead Mixed-Halide Perovskites Revealed by Dynamic Near-Ambient Pressure X-ray Photoelectron Spectroscopy

Herein, we quantify rates of O2-photoactivated corrosion and recovery processes within triple cation CsFAMAPb(IBr)3 perovskite active layers using dynamic near-ambient pressure X-ray photoemission spectroscopy (NAP-XPS). Activated corrosion is described as iodide oxidation and lead reduction, which occurs only in the presence of both O2 and light through photoinduced electron transfer. We observe electron density reorganization from the Pb-I bonds consistent with ligand exchange, evident from the nonstoichiometric redox change (i.e., <1 e-). Approximately half of the Pb centers are reduced to weakly coordinated Pb-higher oxidation number than metallic Pb-with a rate coefficient of ∼3 (±0.3) × 10-4 atomic percent/s. Hole capture by I- yields I3- and is accompanied by increased concentrations of near-surface bromides, hypothesized to be due to anion vacancies and/or oxidation of mobile iodide resulting from ion demixing. Activated corrosion is found to be quasi-reversible; initial perovskite stoichiometry slowly recovers when the O2/light catalyst is removed, postulated to be due to mobile halide species present within the film below XPS sampling depth. Small deviations in near-surface composition (<2%) of the perovskite are used to connect reaction rates to quantified, near-band edge donor and acceptor defect concentrations, demonstrating two energetically distinct sites are responsible for the redox process. Collectively, environmental flux and rate quantification are deemed critical for the future elucidation of chemical degradation processes in perovskites, where rate-dependent reaction pathways are expected to be very system dependent (environment and material).

Gradient Thermal Annealing Assisted Perovskite Film Crystallization Regulation for Efficient and Stable Photovoltaic-Photodetection Bifunctional Device

Perovskite crystallization regulation is essential to obtain excellent film optoelectronic properties and device performances. However, rapid crystallization during annealing always results in poor perovskite film and easy formation of trap, thereby greatly restricting device performance due to severe non-radiative recombination. Here, an easy and reproducible gradient thermal annealing (GTA) approach is used to regulate the perovskite crystallization. Through a low-temperature initial annealing of GTA, the solvent evaporation is slowed down, thus extending nucleation time and providing a buffer for the rapid crystallization of perovskite grains in the subsequent high-temperature stage. As a result, completely converted and highly crystalline perovskite is obtained with 1.6 times larger grain size, reduced trap density and suppressed non-radiative recombination of photo-generated carriers. The film crystallinity is also enhanced with more advantageous (100) and (111) lattice facets which are favorable for carrier transport. Consequently, the perovskite photodetectors exhibit a large linear dynamic range of 174 dB and an excellent response even under ultra-weak light of 303 pW. Meanwhile, perovskite solar cells achieved increased PCE and maintained 85% of original efficiency after heating at 65 °C for nearly 1000 h under unencapsulated conditions. To the knowledge, this represents the best performance reported for a perovskite photovoltaic-photodetection bifunctional device.

A Wenzel Interfaces Design for Homogeneous Solute Distribution Obtains Efficient and Stable Perovskite Solar Cells

The coffee-ring effect, caused by uneven deposition of colloidal particles in perovskite precursor solutions, leads to poor uniformity in perovskite films prepared through large-area printing. In this work, the surface of SnO2 is roughened to construct a Wenzel model, successfully achieving a super-hydrophilic interface. This modification significantly accelerates the spreading of the perovskite precursor solution, reducing the response delay time of perovskite colloidal particles during the printing process. Additionally, the micro-spherical depression structure on the SnO2 surface effectively inhibits the migration of colloidal particles toward the edges of liquid film, trapping perovskite colloidal particles at the buried interfaces and improving film uniformity. Due to the synergistic effect of super-hydrophilicity and micro-rough structure on the surface of SnO2, leading to a substantial improvement in the quality of perovskite crystals. Therefore, the efficiency of printing prepared flexible devices (0.101 cm2) reached 25.42% (certified 25.12%). Moreover, the efficiency of rigid and flexible large-scale perovskite solar modules (PSMs) based on meniscus-coating manufacture reached 21.34% and 16.99% (100 cm2), respectively, and demonstrated superior environmental stability by maintaining an initial efficiency of 91% after being stored in atmospheric conditions for 2000 h, offering practical guidance for fabricating high-performance and stable large-scale perovskite solar cells (PSCs).

Boosting Tin Perovskite Solar Cell Performance via Light-Induced Interface Doping

Continuous breakthroughs have been achieved in the photoelectric conversion efficiency (PCE) of tin-based perovskite solar cells (TPSCs) in recent years. Inspired by performance improvements observed during device storage, we identified beneficial light-induced interface doping (LIID) in the TPSCs. In situ analyses using X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy reveal that ion migration and oxidation at the interface induce beneficial doping effects, enhancing carrier transport and significantly boosting device performance. By implementing specific illumination techniques or maximum power point tracking (MPPT) methods to achieve LIID, we increased the open-circuit voltage while maintaining a high short-circuit current, reaching a PCE of up to 14.91%. Furthermore, this efficiency was sustained at 70% of its maximum value after nearly 900 h of continuous operation. Our study introduces a novel approach to addressing energy band mismatch, paving the way for improved efficiency in tin-based perovskite solar cells.

Top-Down Dual-Interface Carrier Management for Highly Efficient and Stable Perovskite/Silicon Tandem Solar Cells

Despite significant advancements in the power conversion efficiency (PCE) of perovskite/silicon tandem solar cells, improving carrier management in top cells remains challenging due to the defective dual interfaces of wide-bandgap perovskite, particularly on textured silicon surfaces. Herein, a series of halide ions (Cl-, Br-, I-) substituted piperazinium salts are designed and synthesized as post-treatment modifiers for perovskite surfaces. Notably, piperazinium chloride induces an asymmetric bidirectional ions distribution from the top to the bottom surface, with large piperazinium cations concentrating at the perovskite surface and small chloride anions migrating downward to accumulate at the buried interface. This results in effective dual-interface defect passivation and energy band modulation, enabling wide-bandgap (1.68 eV) perovskite solar cells to achieve a PCE of 22.3% and a record product of open-circuit voltage × fill factor (84.4% relative to the Shockley-Queisser limit). Furthermore, the device retains 91.3% of its initial efficiency after 1200 h of maximum power point tracking without encapsulation. When integrated with double-textured silicon heterojunction solar cells, a remarkable PCE of 31.5% is achieved for a 1.04 cm2 monolithic perovskite/silicon tandem solar cell, exhibiting excellent long-term operational stability (T80 = 755 h) without encapsulation in ambient air. This work provides a convenient strategy on dual-interface engineering for making high-efficiency and stable perovskite platforms.

A Chain Entanglement Gelled SnO₂ Electron Transport Layer for Enhanced Perovskite Solar Cell Performance and Effective Lead Capture

SnO₂ is a widely used electron transport layer (ETL) material in perovskite solar cells (PSCs), and its design and optimization are essential for achieving efficient and stable PSCs. In this study, the in situ formation of a chain entanglement gel polymer electrolyte is reported in an aqueous phase, integrated with SnO₂ as the ETL. Based on the self-polymerization of 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propane-1-sulfonic acid (DAES) in an aqueous environment, combining the catalytic effect of LiCl (as a Lewis acid) with the salting-out effect, and the introduction of polyvinylpyrrolidone (PVP) as the other polymer chain, a chain entanglement gelled SnO2 (G-SnO2) structure is successfully constructed with a wide range of functions. The PDEAS-PVP chain entanglement gel achieves passivation and Pb2⁺ capture through chemical chelation mechanisms is explored. The results demonstrated that the all-in-air prepared PSC based on G-SnO2 exhibited an excellent power conversion efficiency (PCE) of 24.77% and retained 83.3% of their initial efficiency after 2100 h of air exposure. Additionally, the PDEAS-PVP exposes more C═O and S═O active sites, significantly enhanced the lead absorption capability of the PSCs.

25.91%-Efficiency and Durable Inverted Perovskite Solar Cells Enabled by a Multifunctional Molecule Mediated Precursor Engineering

The stability of the precursor is essential for producing high-quality perovskite films with minimal non-radiative recombination. In this study, methionine sulfoxide (MTSO), which features multiple electron-donation sites, is strategically chosen as a precursor stabilizer and crystal growth mediator for inverted perovskite solar cells (PSCs). MTSO stabilizes the precursor by inhibiting the oxidation of iodide ions and passivates charged traps through coordination and hydrogen bonding interactions. This leads to enhanced crystallinity, reduced non-radiative recombination, and decreased internal residual stress in perovskite film. As a result, remarkable power conversion efficiencies of 25.91% (certified 25.76%) with a minimal voltage deficit of 0.36 V for a 0.09-cm2 inverted PSC, and 21.96% for a 12.96-cm2 (active area) perovskite minimodule, have been achieved, respectively. Furthermore, the unencapsulated devices demonstrated excellent long-term thermal aging and operational stability, retaining over 90% and 92% of their original efficiencies after 500 h of continuous thermal aging at 85 °C and 2500 h of continuous maximum power point tracking under 1 sun (white light LED array) illumination at 30 ± 5 °C. This study underscores the importance of the rational design of functional molecules for stabilizing the precursor and regulating the crystallization of perovskite films, advancing the practical development of PSCs.

Regulated Crystallization Through Intermolecular Interactions Bridging for Efficient Tin-Based Perovskite Solar Cells

Tin halide perovskite (THP) has emerged as a promising lead-free material for high-performance solar cells, attracting significant attention for their potential use for energy conversion. However, the rapid crystallization of THP due to its high Lewis acidity and easy oxidation of Sn2+ leads to poor morphology and rampant defects in the resulting perovskite films. These strongly hamper the advances in efficiency and stability in THP solar cells. Herein, a comprehensive crystallization regulation strategy is demonstrated by introducing methyl carbazate (C2H6N2O2, MeC) to regulate the crystallization kinetics of perovskite through inter-molecular interactions. The coordination bonds (O…Sn) and hydrogen bonds (N─H…O) between MeC and perovskite bridge the perovskite lattice together, helping suppress the oxidation of Sn2+, meanwhile, restraining the fast crystallization of perovskite in the precursor solution, by enhancing nucleation sites. More importantly, the connection by MeC can reduce the deep-level trap state defect density, significantly restraining non-radiative recombination and improving the carrier lifetime. Consequently, this facile strategy offers valuable insights into THP crystallization kinetics and allows an enhanced high power conversion efficiency from 10.43% to 14.02% to be achieved with good stability.

Transition of Perovskite Solar Technologies to Being Flexible

Perovskite technologies has taken giant steps on its advances in only a decade time, from fundamental science to device engineering. The possibility to exploit this technology on a thin flexible substrate gives an unbeatable power to weight ratio compares to similar photovoltaic systems, opening new possibilities and new integration concepts, going from building integrated and applied photovoltaics (BIPV, BAPV) to internet of things (IoT). In this perspective, the recent progress of perovskite solar technologies on flexible substrates are summarized, focusing on the challenges that researchers face upon using flexible substrates. A dig into material science is necessary to understand what kind of mechanisms are limiting its efficiency compare to rigid substrates, and which physical mechanism limits the upscaling on flexible substrate. Furthermore, an overview of stability test on flexible modules will be described, suggesting common standard procedure and guidelines to follow, showing additional issues that flexible modules face upon bending, and how to prevent device degradation providing an ad-hoc encapsulation. Finally, the recent advances of flexible devices in the perovskite market will be shown, giving an outline of how this technology is exploited on flexible substrates, and what are still missing that need stakeholders' attention.

Understanding the Mechanisms of Methylammonium-Induced Thermal Instability in Mixed-FAMA Perovskites

Despite a recent shift toward methylammonium (MA)-free lead-halide perovskites for perovskite solar cells, high-efficiency formamidinium lead iodide (FAPbI3) devices still often require methylammonium chloride (MACl) as an additive, which evaporates away during the annealing process. In this article, it is shown that the residual MA+, however, triggers thermal instability. To investigate the possibility of an optimal concentration of MA+ that may improve thermal stability, the intrinsic thermal stability of pure FA, FA-rich, MA-rich, and pure MA perovskite films (FA1-xMAxPbI3, FAMA) is studied. The results show that the thermal stability of FAMA perovskites decreases with more MA+, under degradation conditions that isolate the intrinsic thermal stability of the material (i.e., without moisture and oxygen effects). X-ray diffraction (XRD), proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS), photoluminescence (PL) and UV-visible spectroscopy, and depth-profiling X-ray Photoelectron Spectroscopy (XPS) are employed to show that the observed trend is mainly due to the decomposition of the MA+ cation, as opposed to other effects such as the precursor solvent and film morphologies. It is also found that the surfaces of these FAMA films are MA+ rich, although this phenomenon does not appear to affect thermal stability. Finally, it is demonstrated that this trend is unaffected by the presence of Spiro-OMeTAD atop the film, and thus solar cell devices should preserve this trend.

Synergetic Interface and Bulk Defects Modification with Identical Organic Molecule for Efficient Inverted Perovskite Solar Cells

Recent progress in inverted perovskite solar cells (IPSCs) mainly focused on NiOx modification and perovskite (PVK) regulation to enhance efficiency and stability. However, most works address only monofunctional modifications, and identical molecules with the ability to simultaneously optimize NiOx interface and perovskite bulk phase have been rarely reported. This work proposes a dual modification approach using 4-amino-3,5-dichlorobenzotrifluoride (DCTM) to optimize both NiOx upper interfaces and reduction of bulk defects in perovskite. Amino group in DCTM increases the Ni3+/Ni2+ ratio in NiOx, thereby increasing the conductivity and optimizing the energy alignment. Additionally, DCTM fills Pb2+ and I- vacancies in perovskite, which improves the vertical orientation of perovskite grains and subsequently reduces nonradiative recombination, thereby achieving the increased carrier lifetime. PVK modified by DCTM exhibits enhanced energy level alignment with the electron transport layer, while femtosecond transient absorption (TA) spectroscopy confirms that DCTM facilitates efficient carrier transport, leading to high-performance IPSCs. The optimized IPSCs achieve a maximum efficiency of 22.8% with a reduced hysteresis (0.7%). Moreover, the unencapsulated device preserves over 80% of its initial power conversion efficiency (PCE) after 1000 h stored in air at 30% relative humidity. This dual modification strategy of monomolecular offers a straightforward solution for interface optimization and provides new insights into selecting aniline-derived molecules for high-performance IPSCs.

Multifunctional Graphdiyne Enables Efficient Perovskite Solar Cells via Anti-Solvent Additive Engineering

Finding ways to produce dense and smooth perovskite films with negligible defects is vital for achieving high-efficiency perovskite solar cells (PSCs). Herein, we aim to enhance the quality of the perovskite films through the utilization of a multifunctional additive in the perovskite anti-solvent, a strategy referred to as anti-solvent additive engineering. Specifically, we introduce ortho-substituted-4'-(4,4″-di-tert-butyl-1,1':3',1″-terphenyl)-graphdiyne (o-TB-GDY) as an AAE additive, characterized by its sp/sp2-cohybridized and highly π-conjugated structure, into the anti-solvent. o-TB-GDY not only significantly passivates undercoordinated lead defects (through potent coordination originating from specific high π-electron conjugation), but also serves as nucleation seeds to effectively enhance the nucleation and growth of perovskite crystals. This markedly reduces defects and non-radiative recombination, thereby increasing the power conversion efficiency (PCE) to 25.62% (certified as 25.01%). Meanwhile, the PSCs exhibit largely enhanced stability, maintaining 92.6% of their initial PCEs after 500 h continuous 1-sun illumination at ~ 23 °C in a nitrogen-filled glove box.

Highly Oriented and Ordered Co-Assembly Monolayers for Inverted Perovskite Solar Cells

Perovskite solar cells with inverted architecture have remarkable power conversion efficiency (PCE) and operating stability based on self-assembled molecules (SAMs) hole transport layer. Homogeneous distribution and covalent binding mode of SAM monolayers are critical to improving interfacial property and reducing interfacial losses, which can be achieved through molecular design and co-assembly strategy. Here, we propose co-assembly strategy with SAM by employing a novel 2D π-conjugated structure graphdiyne derivative (PAG) with phosphoric acid groups. Through the π-π interaction and hydrogen bonding between PAG and SAM, the enhanced tridentate anchoring and highly ordered molecular orientation perpendicular to the substrate are successfully achieved. The improvement of interfacial characteristics further optimizes the crystalline quality and buried interface properties of perovskite films, allowing us to achieve a remarkable PCE of 26.10 % under standard illumination.

Molecular Design of Hole-Collecting Materials for Co-Deposition Processed Perovskite Solar Cells: A Tripodal Triazatruxene Derivative with Carboxylic Acid Groups

High-performance and cost-effective hole-collecting materials (HCMs) are indispensable for commercially viable perovskite solar cells (PSCs). Here, we report an anchorable HCM composed of a triazatruxene core connected with three alkyl carboxylic acid groups (3CATAT-C3). In contrast to the phosphonic acid-containing tripodal analog (3PATAT-C3), 3CATAT-C3 molecules can form a hydrophilic monolayer on a transparent conducting oxide surface, which is beneficial for subsequent perovskite film deposition in the traditional layer-by-layer fabrication process. More importantly, the larger diffusion coefficient and higher surface energy make 3CATAT-C3 suitable for the simplified, cost-effective one-step co-deposition process in which 3CATAT-C3 was directly added as part of the perovskite precursor solution. 3CATAT-C3 is predominantly located at the perovskite bottom surface after spin-coating the mixed precursor solution, facilitating charge extraction. Devices with 3CATAT-C3 fabricated by this co-deposition method exhibit superior performance with a champion power conversion efficiency of over 23%. The unencapsulated devices showed good operational stability (retaining 90% of the initial output after 100 h), thermal durability (retaining 95% of the initial value after heating at 105 °C under air), and excellent storage stability (showing no drop in performance over 8000 h). Based on the results of time-of-flight secondary-ion mass spectroscopy (ToF-SIMS) and diffusion order nuclear magnetic resonance spectroscopy (DOSY), we elucidated the effect of anchoring groups on the performance of the tripodal HCMs in PSCs as well as the mechanism of the co-deposition fabrication process. Our findings provide valuable insights for the molecular design of multifunctional hole-collecting materials, further advancing the performance of perovskite solar cells.

Rationally designed universal passivator for high-performance single-junction and tandem perovskite solar cells

Interfacial trap-assisted nonradiative recombination hampers the development of metal halide perovskite solar cells (PSCs). Herein, we report a rationally designed universal passivator to realize highly efficient and stable single junction and tandem PSCs. Multiple defects are simultaneously passivated by the synergistic effect of anion and cation. Moreover, the defect healing effect is precisely modulated by carefully controlling the number of hydrogen atoms on cations and steric hindrance. Due to minimized interfacial energy loss, L-valine benzyl ester p-toluenesulfonate (VBETS) modified inverted PSCs deliver a power conversion efficiency (PCE) of 26.28% using vacuum flash processing technology. Moreover, by suppressing carrier recombination, the large-area modules with an aperture area of 32.144 cm2 and perovskite/Si tandem solar cells coupled with VBETS passivation deliver a PCE of 21.00% and 30.98%, respectively. This work highlights the critical role of the number of hydrogen atoms and steric hindrance in designing molecular modulators to advance the PCE and stability of PSCs.

Small molecule induced interfacial defect healing to construct inverted perovskite solar cells with high fill factor and stability

Chemical defects at the surface and grain boundaries of perovskite crystals cause deterioration of conversion efficiency and stability of perovskite solar cells (PSCs). In this study, a multifunctional additive, 5-fluoro-2-pyrimidine carbonitrile (FPDCN) molecule, is added into the perovskite precursor solution in order to passivate the uncoordinated Pb2+ by the cyanogen (-CN) group and pyrimidine N in FPDCN. Interestingly, fluorine (F) atoms interact with FA+ to form hydrogen bonds, which could regulate the perovskite crystallization process for the formation of high-quality perovskite crystals. Besides, the F atoms in FPDCN increase the water contact angle of perovskite films. As a result, the carrier extraction and transport in the perovskite film are significantly enhanced, and the non-radiative recombination is suppressed. The corresponding devices achieve a champion photovoltaic conversion efficiency (PCE) of 20.7 % and a fill factor (FF) of over 83 %. The device based on FPDCN shows long-term stability under a high-humidity atmospheric environment by maintaining 85 % of the initial efficiency after aging of 700 h in the glove box. This study provides a simple and convenient method to prepare stable and efficient PSCs by optimizing the perovskite precursor solution.

Enhancing Charge-Emitting Shallow Traps in Metal Halide Perovskites by >100 Times by Surface Strain

The low density of deep trapping defects in metal halide perovskites (MHPs) is essential for high-performance optoelectronic devices. Shallow traps in MHPs are speculated to enhance charges recombination lifetime. However, it is unknown about the shallow trap chemical nature and distribution, and impact on solar cell operation. Herein, we report that shallow traps are much richer in MHPs than traditional semiconductors. Their density can be enhanced by >100 times through local surface strain, indicating shallow traps mainly located at the surface. The surface strain is introduced by anchoring two-amine-terminated molecules onto formamidinium cations, and the shallow traps are formed by the band edge downshifting toward defect levels. The high-density shallow traps temporarily hold one type of charges and increased concentration of the other type of free carrier in working solar cells by keeping photogenerated charges from bimolecular recombination, resulting in reduced open circuit voltage loss to 317 mV.

High-Performance and Stable Perovskite/Organic Tandem Solar Cells Enabled by Interconnecting Layer Engineering

Perovskite/organic tandem solar cells (PO-TSCs) have recently attracted increasing attention due to their high efficiency and excellent stability. The interconnecting layer (ICL) is of great importance for the performance of PO-TSCs. The charge transport layer (CTL) and the charge recombination layer (CRL) that form the ICL should be carefully designed to enhance charge carrier extraction and promote charge carrier recombination balance from the two subcells. Here, we propose an effective strategy to optimize the ICL by using [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) to modify the poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) as the hole transport layer (HTL) in the ICL. It is found that the coverage state of 2PACz on the PEDOT:PSS significantly affects the performance of PO-TSCs and can be regulated by adjusting the concentration of the 2PACz solution. The PEDOT:PSS/2PACz structure facilitates effective charge carrier extraction from the organic solar cells to the CRL. Herein, for the PO-TSCs, this strategy results in an efficient and balanced charge carrier recombination in the ICL and also allows a thinner PEDOT:PSS with reduced parasitic absorption. As a result, the PO-TSC achieves a power conversion efficiency (PCE) of 25.26%, much higher than the control device (PCE of 23.57%), and better stability. This work demonstrates an effective approach to achieving high-performance PO-TSCs through ICL engineering.

Cyclic Multi-Site Chelation for Efficient and Stable Inverted Perovskite Solar Cells

Trap-assisted non-radiative recombination losses and moisture-induced degradation significantly impede the development of highly efficient and stable inverted (p-i-n) perovskite solar cells (PSCs), which require high-quality perovskite bulk. In this research, we mitigate these challenges by integrating thermally stable perovskite layers with Lewis base covalent organic frameworks (COFs). The ordered pore structure and surface binding groups of COFs facilitate cyclic, multi-site chelation with undercoordinated lead ions, enhancing the perovskite quality across both its bulk and grain boundaries. This process not only reduces defects but also promotes improved energy alignment through n-type doping at the surface. The inclusion of COF dopants in p-i-n devices achieves power conversion efficiencies (PCEs) of 25.64 % (certified 24.94 %) for a 0.0748-cm2 device and 23.49 % for a 1-cm2 device. Remarkably, these devices retain 81 % of their initial PCE after 978 hours of accelerated aging at 85°C, demonstrating remarkable durability. Additionally, COF-doped devices demonstrate excellent stability under illumination and in moist conditions, even without encapsulation.

Functionalized Substrates for Reduced Nonradiative Recombination in Metal-Halide Perovskites

Reducing nonradiative recombination is crucial for minimizing voltage losses in metal-halide perovskite solar cells and achieving high power conversion efficiencies. Photoluminescence spectroscopy on complete or partial perovskite solar cell stacks is often used to quantify and disentangle bulk and interface contributions to nonradiative losses. Accurately determining the intrinsic loss in a perovskite layer is key to analyzing the origins of nonradiative recombination and developing defect engineering strategies. Here, we study perovskite films on glass and indium-tin-oxide-covered glass substrates, functionalized with a range of different molecules, using absolute and transient photoluminescence. We find that grafting these substrates with 1,6-hexylenediphosphonic acid (HDPA) effectively reduces the nonradiative losses in perovskite films for a series of perovskite semiconductors with bandgaps ranging from 1.26 to 2.28 eV. The results suggest that perovskites processed on HDPA-functionalized substrates suffer the least from nonradiative recombination and thus approach the properties of a defect-free semiconductor.

Self-assembled materials with an ordered hydrophilic bilayer for high performance inverted Perovskite solar cells

While self-assembled material based inverted perovskite solar cells have surpassed power conversion efficiencies of 26%, enhancing their performance in large-area configurations remains a significant challenge. In this work, we report a self-assembled material based hole-selective layer 4-(7H-dibenzo[c,g]carbazol-7-yl)phenyl)phosphonic acid, with a π-expanded conjugation. The enhanced intermolecular π-π interactions facilitate the self-assembly of 4-(7H-dibenzo[c,g]carbazol-7-yl)phenyl)phosphonic acid molecules to form an ordered bilayer with a hydrophilic surface, which passivates the buried perovskite interface defect and enables high-quality and large-area perovskite preparation, while simultaneously enhancing interfacial charge extraction and transport. The certified efficiency of 4-(7H-dibenzo[c,g]carbazol-7-yl)phenyl)phosphonic acid based small-area (0.0715 cm2) device is 26.39% with high stability. Furthermore, a certified efficiency of 25.21% is achieved for a 99.12 mm2 large area device.

Visible Light-Triggered Self-Welding Perovskite Solar Cells and Modules

Flexible perovskite solar cells (F-PSCs) are highly promising for both stationary and mobile applications because of their advantageous features, including mechanical flexibility, their lightweight and thin nature, and cost-effectiveness. However, a number of drawbacks, such as mechanical instability, make their practical application difficult. Here, self-welding dynamic diselenide that is triggered by visible light into the structure of F-PSCs to improve their long-term stability by repairing cracks and defects in the absorber layer is incorporated. The diselenide confers the flexibility and self-welding properties to the Cs0.05MA0.05FA0.9PbI3 perovskite layer, enabling optimized F-PSC devices to achieve a power conversion efficiency of 24.85% while retaining ca. 92% of their initial efficiency after undergoing 15 000 bending cycles at a curvature radius of 3 mm. The corresponding flexible large-scale module with an active area of 15.82 cm2 achieved a record PCE of 21.65%.

Stable Surface Contact with Tailored Alkylamine Pyridine Derivatives for High-Performance Inverted Perovskite Solar Cells

Formamidinium-cesium lead triiodide (FA1-xCsxPbI3) perovskite holds great promise for perovskite solar cells (PSCs) with both high efficiency and stability. However, the defective perovskite surfaces induced by defects and residual tensile strain largely limit the photovoltaic performance of the corresponding devices. Here, the passivation capability of alkylamine-modified pyridine derivatives for the surface defects of FA1-xCsxPbI3 perovskite is systematically studied. Among the studied surface passivators, 3-(2-aminoethyl)pyridine (3-PyEA) with the suitable size is demonstrated to be the most effective in reducing surface iodine impurities and defects (VI and I2) through its strong coordination with Npyridine. Additionally, the tail amino group (─NH2) from 3-PyEA can react with FA+ cations to reduce the surface roughness of perovskite films, and the reaction products can also passivate FA vacancies (VFA), and further strengthen their binding interaction to perovskite surfaces. These merits lead to suppressed nonradiative recombination loss, the release of residual tensile stress for the perovskite films, and a favorable energy-level alignment at the perovskite/[6,6]-phenyl-C61-butyric acid methyl ester interface. Consequently, the resulting inverted FA1-xCsxPbI3 PSCs obtain an impressive power conversion efficiency (PCE) of 25.65% (certified 25.45%, certified steady-state efficiency 25.06%), along with retaining 96.5% of the initial PCE after 1800 h of 1-sun operation at 55 °C in air.

Enhancing Hole Transport Uniformity for Efficient Inverted Perovskite Solar Cells through Optimizing Buried Interface Contacts and Suppressing Interface Recombination

[4-(3,6-dimethyl-9H-carbazol-9yl)butyl]phosphonic acid (Me-4PACz) self-assembly material has been recognized as a highly effective approach for mitigating nickel oxide (NiOx) surface-related challenges in inverted perovskite solar cells (IPSCs). However, its uneven film generation and failure to effectively passivate the buried interface defects limit the device's performance improvement potential. Herein, p-xylylenediphosphonic acid (p-XPA) containing bilateral phosphate groups (-PO3H2) is introduced as an interface layer between the NiOx/Me-4PACz and the perovskite layer. P-XPA can flatten the surface of hole transport layer and optimize interface contact. Meanwhile, p-XPA achieves better energy level alignment and promotes interfacial hole transport. In addition, the bilateral -PO3H2 of p-XPA can chelate with Pb2+ and form hydrogen bond with FA+ (formamidinium cation), thereby suppressing buried interface non-radiative recombination loss. Consequently, the IPSC with p-XPA buried interface modification achieves champion power conversion efficiency of 25.87 % (certified at 25.45 %) at laboratory scale (0.0448 cm2). The encapsulated target device exhibits better operational stability. Even after 1100 hours of maximum power point tracking at 50 °C, its efficiency remains at an impressive 82.7 % of the initial efficiency. Molecules featuring bilateral passivation groups optimize interfacial contact and inhibit interfacial recombination, providing an effective approach to enhancing the stability and efficiency of devices.

Modelling and Numerical Evaluation of Photovoltaic Parameters of a Highly Efficient Perovskite Solar Cell Based on Methylammonium Tin Iodide

Designing a high-performance solar cell structure requires the understanding of material innovation, device engineering, charge behavior, operation characteristics and efficient photoconversion of light to generate electricity. This study offers a detailed numerical evaluation of the device physics in a highly efficient methylammonium-based perovskite solar cell (PSC) of the configuration, FTO/WO3/CH₃NH₃SnI₃/GO/Fe. Utilizing the SCAPS-1D device simulator, an impressive open-circuit voltage (Voc) of 1.3184 V, short-circuit current density (Jsc) of 35.10 mA/cm2, Fill factor (FF) of 78.38 %, and power conversion efficiency (PCE) of 36.24 % were achieved. The model cell exhibits a robust photon capture of 100 % quantum efficiency between 360 and 750 nm. The study also presents a temperature-dependent band alignment diagram which posted a built-in potential (Vbi) of 0.62 eV. The Vbi at 400 K was found to be 0.58 eV indicating that the model cell exhibits a decent temperature tolerance, and can retain approximately 93 % of its power at 400 K. Through Mott-Schottky capacitance analysis, deeper insights into the space-charge region are inferred, while recombination-generation investigations emphasize the significance of electronic properties in optimizing device performance. This paper, therefore, lays the foundation for future studies, offering clear pathways for device optimization and identifying key areas that require further investigation.

One-Stone-For-Three-Birds Strategy Using a Fullerene Modifier for Efficient and Stable Inverted Perovskite Solar Cells

The electron extraction from perovskite/C60 interface plays a crucial role in influencing the photovoltaic performance of inverted perovskite solar cells (PSCs). Here, we develop a one-stone-for-three-birds strategy via employing a novel fullerene derivative bearing triple methyl acrylate groups (denoted as C60-TMA) as a multifunctional interfacial layer to optimize electron extraction at the perovskite/C60 interface. It is found that the C60-TMA not only passivates surface defects of perovskite via coordination interactions between C=O groups and Pb2+ cations but also bridge electron transfer between perovskite and C60. Moreover, it effectively induces the secondary grain growth of the perovskite film through strong bonding effect, and this phenomenon has never been observed in prior art reports on fullerene related studies. The combination of the above three upgrades enables improved perovskite film quality with increased grain size and enhanced crystallinity. With these advantages, C60-TMA treated PSC devices exhibit a much higher power conversion efficiency (PCE) of 24.89 % than the control devices (23.66 %). Besides, C60-TMA benefits improved thermal stability of PSC devices, retaining over 90 % of its initial efficiency after aging at 85 °C for 1200 h, primarily due to the reinforced interfacial interactions and improved perovskite film quality.

Exploring the Potential and Hurdles of Perovskite Solar Cells with p-i-n Structure

The p-i-n architecture within perovskite solar cells (PSCs) is swiftly transitioning from an alternative concept to the forefront of perovskite photovoltaic technology, driven by significant advancements in performance and suitability for tandem solar cell integration. The relentless pursuit to increase efficiencies and understand the factors contributing to instability has yielded notable strategies for enhancing p-i-n PSC performance. Chief among these is the advancement in passivation techniques, including the application of self-assembled monolayers (SAMs), which have proven central to mitigating interface-related inefficiencies. This Perspective delves into a curated selection of recent impactful studies on p-i-n PSCs, focusing on the latest material developments, device architecture refinements, and performance optimization tactics. We particularly emphasize the strides made in passivation and interfacial engineering. Furthermore, we explore the strides and potential of p-i-n structured perovskite tandem solar cells. The Perspective culminates in a discussion of the persistent challenges facing p-i-n PSCs, such as long-term stability, scalability, and the pursuit of environmentally benign solutions, setting the stage for future research directives.

Recent progress of buried interface in high-efficiency and stable perovskite solar cells

Perovskite solar cells (PSCs) have been rapidly developed in recent years due to their excellent photovoltaic performance, which has been actively promoted by many researchers. However, interfacial non-radiative compounding hinders further improvement of their device performance. Buried interface modification strategies can minimize the non-radiative compounding within the interface, resulting in highly efficient and stable PSCs. In this review, we summarize the recent advances in the development of multiple classes of materials applied to buried interface engineering for the preparation of highly efficient and stable PSCs, including the development of organic, inorganic, and polymeric materials. The important role of buried interfaces in regulating energy alignment, passivating surface defects, modulating morphology, etc. have been discussed. Furthermore, we propose strategies to reduce nonradiative composites at interfaces. Finally, potential developments and challenges of buried interfaces for high performance stabilized PSCs are presented.

Efficient and Stable p-i-n Perovskite Solar Cells Enabled by In Situ Functional Group Conversion

Chemical additives play a critical role in the crystallization kinetics and film morphology of perovskite solar cells (pero-SCs), thus affecting the device performance and stability. Especially, carboxylic acids and their congeners with a -COOH group can effectively serve as ligands to fortify the structural integrity and mitigate the risk of lead efflux. However, direct addition of -COOH into the precursor solution could retard the crystallization kinetics of the perovskite during film formation due to the strong coordination. Here, we present a novel approach of in situ functional group conversion using Bis(2,5-dioxopyrrolidin-1-yl) 4,7,10,13-tetraoxahexadecanedioate (Bis-PEG4-NHS ester) as an additive in the antisolvent, which underwent a functional group transformation from -COOR to -COOH during the annealing process through a hydrolysis reaction of Bis-PEG4-NHS ester. The corresponding hydrolysates exhibit enhanced interactions with PbI2 and FAI, contributing to the structural integrity and the defect passivation. Our findings offer valuable insights into the chemical interactions within the crystal growth process, achieving the p-i-n pero-SC device with an efficiency of 25.79% (certified as 25.47%) and notable long-term stability.

High-Quality Thiophene-Based Two-Dimensional Perovskite Films Prepared with Dual Additives and Their Application in Solar Cells

This study explores the optimization of (TMA)2MA4Pb5I16 perovskite films by regulating the film quality through the addition of MACl and MAAc additives. We found that adding MACl resulted in a film of larger grains with a power conversion efficiency (PCE) of 5.34%, while excessive MACl led to the formation of low-dimensional phases. Adding 7.5% MAAc improved the film quality with a PCE of 5.64%, although excessive MAAc induces pores and smaller grains. To address these issues, we proposed the combined use of MACl and MAAc additives, resulting in films with a larger grain size, smoother surface, and denser structure. Remarkably, the addition of MAAc + MACl achieved a champion PCE of 8.86% with good reproducibility. Mechanism studies revealed that TMA and MAAc formed a stable complex with PbI2 in solution, disrupting nucleation laws and promoting the formation of nuclei, leading to denser films with smaller grains. Additionally, the MACl treatment effectively promoted grain growth, resulting in high-quality films. This study presents novel insights into dual additive usage and their role in film crystallization, offering valuable guidance for the preparation of high-performance perovskite films.

Polymeric Charge-Transporting Materials for Inverted Perovskite Solar Cells

Inverted perovskite solar cells (PSCs) hold exceptional promise as next-generation photovoltaic technology, where both perovskite absorbers and charge-transporting materials (CTMs) play critical roles in cell performance. In recent years, polymeric CTMs have played an important role in developing efficient, stable, and large-area inverted PSCs due to their unique properties of high conductivity, tunable structures, and mechanical flexibility. This review provides a comprehensive overview of polymeric CTMs used in inverted PSCs, encompassing polymeric hole transport materials (HTMs) and electron transport materials (ETMs). the relationship between their molecular structures, modification strategies are systematically summarized and analyzed for adjusting energy levels, and improving charge extraction, enabling a deep understanding of these widely used materials. The review also explores effective strategies for designing even more efficient polymeric CTMs. Finally, an outlook is proposed on the exciting research of novel polymeric CTMs, paving the way for their commercialized applications in PSCs.

Tetrapodal Hole-Collecting Monolayer Materials Based on Saddle-Like Cyclooctatetraene Core for Inverted Perovskite Solar Cells

Hole-collecting monolayers have greatly advanced the development of positive-intrinsic-negative perovskite solar cells (p-i-n PSCs). To date, however, most of the anchoring groups in the reported monolayer materials are designed to bind to the transparent conductive oxide (TCO) surface, resulting in less availability for other functions such as tuning the wettability of the monolayer surface. In this work, we developed two anchorable molecules, 4PATTI-C3 and 4PATTI-C4, by employing a saddle-like indole-fused cyclooctatetraene as a π-core with four phosphonic acid anchoring groups linked through propyl or butyl chains. Both molecules form monolayers on TCO substrates. Thanks to the saddle shape of a cyclooctatetraene skeleton, two of the four phosphonic acid anchoring groups were found to point upward, resulting in hydrophilic surfaces. Compared to the devices using 4PATTI-C4 as the hole-collecting monolayer, 4PATTI-C3-based devices exhibit a faster hole-collection process, leading to higher power conversion efficiencies of up to 21.7 % and 21.4 % for a mini-cell (0.1 cm2) and a mini-module (1.62 cm2), respectively, together with good operational stability. This work represents how structural modification of multipodal molecules could substantially modulate the functions of the hole-collecting monolayers after being adsorbed onto TCO substrates.