Highly efficient p-i-n perovskite solar cells that endure temperature variations

Surface-driven phase transition of Cs4PbBr6 nanocrystals in droplets: a humidity-responsive mechanism and its application in information security

Zero-dimensional perovskite Cs4PbBr6 nanocrystals have attracted considerable attention for their potential in optoelectronic and sensing applications due to their excellent optoelectronic properties and environmental stability. However, their non-emissive property has limited their development in luminescent applications. Fortunately, the reversible phase transition between Cs4PbBr6 and CsPbBr3 nanocrystals provides a promising strategy to address this limitation. This study investigates the phase transition mechanism induced by the micro-environment factors, with a particular focus on the evolution of optical properties. Small droplets of Cs4PbBr6 nanocrystals were exposed to air, and real-time monitoring of their color changes and photoluminescent emission characteristics was conducted. The results reveal that the large surface area of the droplet facilitates solvent evaporation, which accelerates the phase transition of Cs4PbBr6 nanocrystals, leading to a significant enhancement in photoluminescent brightness. By quantitatively correlating environmental humidity with the phase conversion rate, this work highlights the critical role of humidity in modulating the conversion kinetics. Furthermore, the study systematically explores the mechanism of tuning the photoluminescent emission peak by adjusting the surface ligands, which enables the development of an environment-responsive, color-changing optical device based on droplet dynamics.

Aminomethyl Phosphonic Acid as Highly Effective Multifunctional Additive for Modification of Electron Transport Layer and Perovskite in Photovoltaic Solar Cells

The passivation of detrimental perovskite-based defects is critically acknowledged for fabricating highly effective perovskite solar cells (PSCs). The presence of a high-quality electron transport layer (ETL) is also considered a pivotal factor for effective charge extraction and transport dynamics. Herein, a simple small organic molecule, aminomethyl phosphonic acid (AMPA), is introduced as a multifunctional additive in the SnO2 ETL. The defects in the SnO2 ETL are effectively suppressed by passivating the oxygen vacancies upon the SnO2 surface. Simultaneously, the carrier mobility and crystallinity of SnO2 are enhanced, and the upward-regulated conduction band minimum (CBM) is beneficial for constructing a favorable energy level alignment with the perovskite layer. Notably, the introduced residuals on the SnO2 surface can function as crystalline seeds for growth of large perovskite grains, which can passivate the defects in the perovskite bulk phase, boundaries, as well as the SnO2/perovskite interface. Consequently, the power conversion efficiency (PCE) value of the AMPA-modified PSCs is enhanced from 19.91% to 24.22%. Most importantly, the unencapsulated PSCs with AMPA maintained 94.9% of the initial PCE during 720 h of storage at a relative humidity of 10%, attributed to the improved hydrophobicity of both the SnO2 and perovskite layers after AMPA modification.

Fluid Chemistry of Metal Halide Perovskites

Solution-processed metal halide perovskites (MHPs) have been rapidly developed worldwide, with much attention to fluid dynamic, fluid crystallization, and fluid interfaces, all falling within the realm of fluid chemistry. It is widely recognized that the theory of fluid chemistry has been proven to provide an effective means for the improvement of perovskite crystallization and the enhancement of perovskite solar cells (PSCs) performance. In this review, the fluid behavior, microfluidic synthesis, and aging process of perovskite materials are first investigated, with emphasis on the related improvement methods and chemical mechanisms. Second, the internal crystallization chemistry, external interface chemistry, and the large-area PSCs based on the fluid chemistry are discussed. Finally, four specific directions for future studies of fluid chemistry of MHPs are proposed, aiming to harness the theoretical advantages of fluid chemistry and contribute to the industrialization of PSCs.

Synergistic Effect of Cation and Anion Passivation Defects and Suppression of Phase Transition Enhance the Performance and Stability of Inverted Perovskite Solar Cells

The trap states and phase instability of perovskite films harm the fabrication of high-performance and stable perovskite solar cells (PSCs). Herein, the β-fluorophenylethanammonium cation (β-FPEA+) and tosylate anions (TsO-) are employed to enhance both the performance and stability of inverted PSCs. Theoretical calculations show that β-FPEA+TsO- can passivate the defects at both FA-I and Pb-I terminals. Nuclear magnetic resonance reveals strong interactions between β-FPEA+TsO- and perovskites, which facilitate the fabrication of high-quality perovskite films. During crystallization, β-FPEA+ preferentially generates the 2D perovskite, stabilizing the black phase and passivating defects of the perovskite film. Meanwhile, the large TsO- can be extruded to the grain boundary and surface, reducing trap states and inhibiting the degradation of the perovskite film. The synergistic effect of β-FPEA+ and TsO- passivation on defects and suppression of phase transition results in the power conversion efficiency (PCE) improved to 25.47% (vs 23.08% of the control), along with the unencapsulated device retaining 81% of initial PCE after 960 h at 85 °C in vacuum. This work provides a novel and simple strategy for designing the combination of large organic cations and non-halogenated anions to passivate the defects and suppress phase transition, thereby achieving high performance and stable PSCs.

In Situ Film Stress Measurements Capture Increased Photostability in Additive-Engineered Mixed-Halide Perovskites

Mixed-halide perovskites segregate into iodide- and bromide-rich phases under light and have limited long-term reliability. We report for the first time on mechanical instability originating from illumination, which is monitored through thin-film stress measurements, both ex situ and in situ. We show that low-cost polymer additives, namely, corn starch and polyvinylpyrrolidone, not only induce a desirable compressive intrinsic stress in the thin film but also suppress the photoactivated phenomenon. The additives show no significant changes in stress and photoluminescence (PL) responses when the perovskite films are illuminated under ambient conditions. The controlled real-time in situ monitoring of the relative changes in stress quantifies mechanical durability under 1 sun illumination cycles. We therefore demonstrate a facile route to a photostable mixed-halide perovskite thin film using a scalable deposition technique with a quench-free processing route using nontoxic additives.

Dissolvable molecular bridges promoting buried interface modification for high-performance inverted perovskite solar cells

Non-radiative recombination and suboptimal interfacial contact at the hole transportation layer (HTL)/perovskite interface critically suppress the device performance and stability of inverted perovskite solar cells (PSCs). Herein, we proposed a dissolvable molecular bridge (DMB) strategy by introducing 4-fluorobenzylphosphonic acid (4F-BPA) on the HTL for synergetic buried interface modification, aiming at both defect passivation and interfacial contact enhancement. Comprehensive characterizations and analyses revealed that approximately 80% of 4F-BPA on the HTL was dissolved into the perovskite precursor, promoting controlled crystallization through intermediate phase formation and predominantly accumulating at the HTL/perovskite interface, where it strongly coordinated with lead(II) cations to enhance the interfacial contact and align the energy levels. As a result, the champion device achieved a power conversion efficiency (PCE) of 25.10% with a fill factor of 84.23%. The unencapsulated devices (also without a UV filter) maintained 87.1% of their initial PCE after 1000 h of maximum power point tracking under 1 sun illumination (ISOS-L-1I) and retained 92.7% of their initial PCE after 1000 h in the dark storage test (ISOS-D-1). The DMB strategy establishes a universal and cost-efficient framework for buried interface engineering, unlocking new possibilities for large-area device fabrication and industrial-scale implementation.

An In Situ Polymerization Strategy to Enhance Thermal Stability of Perovskite Solar Cells

The limited operational stability of perovskite solar cells (PSCs) remains the primary obstacle to their commercialization. Introducing organic molecules with coordination and hydrogen bonding has been demonstrated as an effective strategy for enhancing the stability of PSCs. Herein, we introduced acrylamides into the perovskite precursor solution, enabling in situ polymerization to form polyacrylamide at grain boundaries without sacrificing the crystal quality of perovskite films. The -C = O and -NH2 functional groups in polyacrylamide form coordination bonds and hydrogen bonds with uncoordinated Pb2+ and I- at grain boundaries, respectively. The nonradiative recombination has been obviously suppressed, with the efficiency improved from 24.55to 25.85%. Notably, the introduction of polyacrylamide transformed the lattice strain from a large tensile to compressive stress, significantly improving the thermal stability of perovskite films. The polyacrylamide modified device exhibited less than 3% efficiency degradation after continuous heating at 65 °C for 500 h, whereas the control device showed a loss of over 40% within 300 h. The results suggest that the in situ polymerization strategy holds great promise for enhancing the stability and efficiency of PSCs, thus advancing their path toward commercialization.

Challenges and opportunities for the characterization of electronic properties in halide perovskite solar cells

Characterisation of the electronic properties of halide perovskites is often a dilemma for researchers. Many of the data analysis methods for the most common techniques in semiconductor device physics have a small validity window or are generally only applicable to classical doped semiconductors. As alternative data analysis approaches are often prohibitively complicated and require numerical simulations of electronic and often ionic charge carriers, the analysis of data is performed qualitatively and comparatively. The overarching idea is that even if data analysis methods do not apply to a given sample, the trend should still be maintained. However, even this last statement may not be correct in certain situations. Hence, the present review provides a summary of the canonical, frequently used methods to characterise electronic properties in halide perovskites and provides a short explanation of the pitfalls in applying the method, as well as the opportunities that arise from using these methods in ways that are not yet common in the current literature.

Heat-Triggered Dynamic Self-Healing Framework for Variable-Temperature Stable Perovskite Solar Cells

Metal halide perovskite solar cells (PSCs) are promising as the next-generation photovoltaic technology. However, the inferior stability under various temperatures remains a significant obstacle to commercialization. Here, a heat-triggered dynamic self-healing framework (HDSF) is implemented to repair defects at grain boundaries caused by thermal variability, enhancing PSCs' temperature stability. HDSF, distributed at the grain boundaries and surface of the perovskite film, stabilizes the perovskite lattice and releases the perovskite crystal stress through the dynamic exchange reaction of sulfide bonds. The resultant PSCs achieved a power-conversion efficiency (PCE) of 26.32% (certified 25.84%) with elevated temperature stability, retaining 88.7% of the initial PCE after 1000 h at 85 °C. In a variable temperature cycling test (between -40 and 80 °C), the HDSF-treated device retained 87.6% of its initial PCE at -40 °C and 92.6% at 80 °C after 160 thermal cycles. This heat-triggered dynamic self-healing strategy could significantly enhance the reliability of PSCs in application scenarios.

Pushing the boundary of the stability and band gap Pareto front by going towards high-entropy perovskites

Lead-free Cs2BX6 (B = Zr4+, Sn4+, Te4+, Hf4+, Re4+, Os4+, Ir4+, and Pt4+ and X = Cl-, Br-, and I-) vacancy-ordered double perovskites have gained significant attention due to their high performance in solar cell devices. Besides mitigating toxicity concerns associated with the use of lead, the presence of a formally tetravalent B-site in Cs2BX6 has been demonstrated to improve the stability against air and moisture. Recently, experimental studies have shown that high-entropy forms of vacancy-ordered double perovskites can be synthesized and stabilized at room temperature, which opens new opportunities for designing better solar cell absorbers. In this work, we employed high throughput density functional theory (DFT) calculations using the HSE06 hybrid functional to study 546 medium-to-high-entropy vacancy-ordered double perovskites. Our results show that Cs2{B1B2B3B4}1X6 and Cs2{B1B2B3B4}1{XX'}6 perovskites can break the existing linear scaling relationships between the bandgap and formation energy observed in the pure Cs2BX6 and Cs2B{XX'}6 perovskites, which enables materials that simultaneously exhibit an optimal band gap of ∼1.3 eV for single-junction solar cells along with a low formation energy. Electronic structure analysis reveals that this can be attributed to the weak coupling between the BX6 octahedra in Cs2{B1B2B3B4}1X6 and Cs2{B1B2B3B4}1{XX'}6. Based on these findings, we identified the analytical equations that can be used to efficiently predict the band gap and formation energy of high-entropy perovskites from their constituent pure perovskites. Our study offers simple and practical guidelines for the design and synthesis of novel high-entropy perovskites with improved photovoltaic performance.

Molecular polymerization strategy for stable perovskite solar cells with low lead leakage

Lead leakage and stability are the main challenges for the commercialization of perovskite solar cells (PSCs). Here, we propose adding N,N'-bis(acryloyl)cystamine (BAC) to the perovskite precursor solution, which facilitates the formation of polymer BAC (PBAC) at the grain boundaries during the annealing process of films. The PBAC can effectively passivate the defects and reduce the risk of lead leakage. Consequently, the PBAC-modified PSCs achieve an efficiency of 25.53% (0.1 square centimeters) (certified efficiency of 25.24%) and 24.03% (1.0 square centimeters). Moreover, after 1500 hours of continuous maximum power point tracking under simulated AM 1.5 illumination and 2000 hours of exposure to damp heat conditions (85°C and 85% relative humidity), the device retains approximately 96 and 81% of its initial power conversion efficiency, respectively. In addition, PBAC can effectively reduce lead leakage by nearly 72% by immersing the PSCs in water for 480 minutes.

Improving the Stability of Wide Bandgap Perovskites: Mechanisms, Strategies, and Applications in Tandem Solar Cells

Tandem solar cells (TSCs) based on wide bandgap (WBG) perovskites have gained significant attention for their higher power conversion efficiency (PCE) compared to single-junction cells. The role of WBG perovskite solar cells (PSCs) as the sub-cell in tandem cells consists of absorbing high-energy photons and producing higher open-circuit voltages (VOC). However, WBG PSCs face serious phase separation issues, resulting in poor long-term stability and substantial VOC loss in TSCs. In response, researchers have developed a range of strategies to mitigate these challenges, showing promising progress, and a comprehensive review of these strategies is expected. In this review, we discuss the stability mechanism in organic-inorganic hybrids and all-inorganic WBG perovskites. Additionally, we conduct an in-depth investigation of various strategies to enhance stability, including component engineering, additive engineering, interface engineering, dimension control, solvent engineering, and encapsulation. Furthermore, the application of the WBG sub-cell in various TSCs is summarized in detail. Finally, perspectives are provided to offer guidance for the development of efficient and stable WBG sub-cell in the field of TSCs.

SN2-Reaction- Bonding-Heterointerface Strengthens Buried Adhesion and Orientation for Advanced Perovskite Solar Cells

Traditionally weak buried interaction without customized chemical bonding always goes against the formation of high--quality perovskite film that highly determines the efficiency and stability of perovskite solar cells. To address this issue, herein, we propose a bimolecular nucleophilic substitution reaction (SN2) driving strategy to idealize the robust buried interface by simultaneously decorating underlying substrate and functionalizing [PbX6]4- octahedral framework with iodoacetamide and thiol molecules, respectively. Theoretical and experimental results demonstrate that a strong SN2 reaction between exposed halogen and thiol group in two molecules occurs, which not only benefits the reinforcement of buried adhesion, but also triggers target-point-oriented crystallization, synergistically upgrading the upper perovskite film quality and accelerating interfacial charge extraction-transfer behavior. Benefiting from the suppressed nonradiative recombination, as a result, an all-air-processed carbon-based all-inorganic CsPbI2Br device achieves an enhanced efficiency of 15.14 %, more importantly, with significantly prolonged long-term stability under harsh conditions. This unique reaction-driven buried interface provides a new path for manipulating perovskite growth and obtaining advanced perovskite photovoltaics.

Toughened Interface by Engineering the Side Group of Conjugated Polymers to Stabilize Flexible Perovskite Solar Modules

Perovskite solar cells (PSCs) have attracted considerable attention due to their high power conversion efficiency (PCE), cost-effective manufacturing processes, as well as the potential flexibility. However, a significant challenge to the commercial applications of PSCs is their mechanical reliability. In this work, three naphthalene diimide polymers with distinct donor units are chosen to reduce surface trap states and enhance the long-term stability and mechanical reliability of photovoltaic devices. The champion rigid PSCs incorporating conjugated polymers achieved a 373% increase of adhesion toughness at the interface, with a champion PCE of 25.5% for a 0.16 cm2 single cell and 22.3% for a 30.9 cm2 module and retain 97% of the initial efficiency after 2000 h of continuous light soaking. Especially, the flexible PSCs exhibited improved mechanical stability, achieving a champion PCE of 24.8% for a 0.16 cm2 single cell and 20.3% for a 27.9 cm2 module, maintaining 95% of the initial efficiency after 5,000 bending cycles. This study highlights the potential of interfacial conjugated polymer in enhancing the efficiency and stability of PSCs.

Enhancing α-FAPbI3 Crystallization and Photovoltaic Performance through Inhibiting MFA Formation

Methylammonium chloride (MACl) additive is almost irreplaceable in high-performance formamidinium (FA) perovskite photovoltaics. However, the byproduct of methyl formamidinium (MFA+) from the reaction of MA0 and FA damages the compositional purity and phase stability of α-FAPbI3. The addition of iodine (I2) to the FAPbI3 precursor has been reported to inhibit the formation of the byproduct MFA+. Here, we systematically investigate the effect of MAI on perovskite films and devices by using MAI to replace MACl and I2. The results demonstrate that the addition of MAI produces more I3- in the perovskite precursor, which inhibits the reaction between MA and FA and thus blocks the formation of MFA+. Meanwhile, MFA+ formation is reduced due to the delayed MACl evaporation caused by its strong interaction with I3-, facilitating the growth of α-FAPbI3 with an improved bottom morphology. It eliminates unreacted PbI2, forming a homogenized phase, and facilitates ordered growth along the (111) facet, enhancing charge transport and increasing the open-circuit voltage (VOC). The optimized device shows a 2% improvement in PCE, with the VOC increasing from 1.050 to 1.103 V. Additionally, the target device retains 97% of initial performance after 5495 min operation under maximum power point tracking, compared to 82.3% after 2000 min for the control device. This work provides insights into inhibiting the formation of MFA+ byproducts induced by the MA-FA side reaction following the introduction of MACl.

Tailored Lattice-Matched Carbazole Self-Assembled Molecule for Efficient and Stable Perovskite Solar Cells

Self-assembled monolayer molecules have been widely employed as interfacial transport materials in inverted perovskite solar cells (PSCs), demonstrating high efficiency and improved device stability. However, self-assembling monolayer (SAM) molecules often suffer from aggregation and weak interactions with the perovskite layer, resulting in inefficient charge transfer and significant energy losses, ultimately limiting the power conversion efficiency and long-term stability of perovskite solar cells. In this work, we developed a series of novel skeleton-matching carbazole isomer SAMs based on the following key design principles: (1) introducing a benzene ring structure to distort the molecular skeleton of the SAM, thereby preventing aggregation and achieving a uniform distribution on fluorine-doped tin oxide (FTO) substrates; (2) strategically incorporating methoxy groups onto the benzene ring at different positions (ortho, meta, and para). These functional groups not only increase anchoring points with the perovskite layer but also fine-tune the molecular dipole moment. Among the SAMs, m-PhPACz exhibits the most favorable properties, with a maximum dipole moment of 2.4 D and an O-O distance that aligns excellently with the diagonal lead ions in the adjacent perovskite lattice, thereby enhancing SAM-perovskite interactions, facilitating efficient charge extraction, and improving interfacial stability. As a result, the new SAM-based PSCs achieved an impressive power conversion efficiency of 26.2%, with 12.9% improvement. Moreover, the devices demonstrated outstanding photothermal stability, retaining 96% of their initial PCE after 1000 h at 85 °C and maintaining 90% of their initial PCE after 300 h of UV-light exposure.

In-Situ Cross-Linked Polymers for Enhanced Thermal Cycling Stability in Flexible Perovskite Solar Cells

Flexible perovskite solar cells (FPSCs) are a promising emerging photovoltaic technology, with certified power conversion efficiencies reaching 24.9 %. However, the frequent occurrence of grain fractures and interface delamination raises concerns about their ability to endure the mechanical stresses caused by temperature fluctuations. In this study, we employ an in situ polymerization molecule with extended functional end groups to preserve mechanical integrity during thermal cycling. The AMPS-DEA molecule chemically anchors to grain boundaries and cross-links neighboring grains, protecting the structure from stress accumulation. Additionally, its hydroxyl groups form bidentate chelation with SnO2, enhancing interfacial adhesion and preventing delamination. More importantly, the relaxed residual stress provided by AMPS-DEA allows the perovskite layer to adapt to temperature changes, effectively matching adjacent layers and preventing mechanical failure. Our findings demonstrate that AMPS-DEA modification not only boosts PCE to 25.78 % in rigid PSCs and 24.54 % in flexible PSCs but also improves stability, maintaining over 95 % efficiency after 10,000 bending cycles and 200 thermal cycles.

In situ Polymerization Induced Seed-Root Anchoring Structure for Enhancing Stability and Efficiency in Perovskite Solar Modules

The escape of organic cations over time from defective perovskite interface leads to non-stoichiometric terminals, significantly affecting the stability of perovskite solar cells (PSCs). How to stabilize the interface composition under environmental stress remains a grand challenge. To address this issue, we utilize thiol-functionalized particles as a "seed" and conduct in situ polymerization of 2,2,3,4,4,4-hexafluorobutyl methacrylate (HFMA) as a "root" at the bottom of the perovskite layer. In this process, the thiol group acts as the initiation site for the polymerization of HFMA, while the fluorine groups in HFMA firmly anchor the organic cations of the perovskite through multiple hydrogen bonds. This strategy resembles how seeds take root in soil to prevent soil erosion. This bionic seed-rooting structure effectively stabilizes the stoichiometry of the perovskite, thus suppressing the escape of organic cations. As a result, the perovskite films with seed-rooting structures exhibit enhanced stability under harsh vacuum thermal conditions (150 °C, <10 Pa). The resulting PCS achieves an efficiency of 25.64 % and a 22.4 cm2 module efficiency of 22.61 %. After 1300 hours of 1-sun illumination at 85 % relative humidity and 65 °C (ISOS-L-3 protocol), the perovskite solar module maintains 90 % of its initial efficiency.

Enhanced UV Stability of Perovskite Solar Modules via Downshifting Luminescent Organic-Inorganic Copper Halide Film with Near-Unity Efficiency

Obtaining efficient perovskite solar modules (PSMs) with enhanced UV stability is essential for their practical applications, yet remains a significant challenge. In this work, a highly efficient organic-inorganic copper halide downshifting film that significantly enhances the UV stability of PSMs is demonstrated by converting high-energy harmful UV photons into beneficial visible light photons that contribute to photovoltaic performance. The tetrapropylammonium (TPA) cation is selected as the main framework to synthesize a series of organic-inorganic copper halides, denoted as BrxIy. A near-unity photoluminescence quantum yield (PLQY) of 99.51% can be achieved by precisely controlling the Br/I ratio to 2:4, denoted as Br2I4, which is one of the highest values reported to date. The dual self-trapped excitons (STEs) luminescence mechanism is systematically investigated by both temperature-dependent and pressure-dependent photoluminescence experiments. This dual-STEs mechanism enables the Br2I4 film to efficiently absorb UV photons and re-emit visible photons, thereby mitigating the photodegradation of PSMs induced by high-energy UV light. Finally, the Br2I4 film is demonstrated effective as a downshifting layer. The PSMs with Br2I4 film achieved an optimal efficiency of 22.24%, maintaining over 90% of their initial efficiency after exposure to a total UV dose of 66.07 kWh m-2.

One-step Centimeter-Scale Growth of Sub-100-nm Perovskite Single-Crystal Arrays in Ambient Air for Color Painting

Halide perovskite single crystals have demonstrated enormous potential for next-generation integrated optoelectronic devices. However, there is a lack of a facile method to realize the controllable growth of large-scale, high-quality, and high-resolution perovskite single crystal arrays on diverse types of substrates, which hinders their application in practical scenarios. Here, a one-step wettability-guided blade coating approach is reported for the rapid in situ crystallization of large-scale, multicolor, and sub-100 nm perovskite single-crystal arrays in the ambient environment. By this strategy, the physical dimensions of perovskite single crystals can be precisely regulated from 90 to 260 nm, with a size variation coefficient < 10% and an area of over 900 mm2. All three typicalhalogen perovskites for multi-color luminescence, CsPbX3 (X = Cl, Br, I) and their mixtures (Cl/Br or Br/I systems), are appliable to this fabrication process through the demonstration of complex RGB patterns with remarkable photoluminescence properties. Moreover, various rigid substrates such as silicon oxide (SiO2), silicon (Si), and glass can also be used to construct the wettability-constrast templates where perovskite crystal nucleate and grow. After that, the perovskite single-crystal arrays or complex patterns can be transferred onto flexible substrates, for instance, COC. This method combines convenient solution processing with conventional photolithography to prepare the high-resolution, large-area, and superior-quality perovskite single crystal arrays in a high-throughput manner, showing great potential in the integration of perovskite nano-optoelectronic devices and chips.

Enhanced Efficiency and Stability of Tin Halide Perovskite Solar Cells Through MOF Integration

Tin halide perovskites are promising candidates for lead-free perovskite solar cells due to their ideal bandgap and high charge-carrier mobility. However, poor crystal quality and rapid degradation in ambient conditions severely limit their stability and practical applications. This study demonstrates that incorporating UiO-66, a zirconium-based MOF, significantly enhances the performance and stability of tin halide perovskite solar cells (TPSCs). The unique porous structure and abundant carboxylate groups of UiO-66 improve the crystallinity and film quality of FASnI₃, reduce defect density, and prolong charge carrier lifetimes. Consequently, the power conversion efficiency (PCE) of UiO-66-integrated TPSCs increases from 11.43% to 12.64%, and the devices maintain over 90% of their initial PCE after 100 days in a nitrogen glovebox. These findings highlight the potential of UiO-66 in addressing the efficiency and stability challenges of tin halide perovskites.

Buried hole-selective interface engineering for high-efficiency tin-lead perovskite solar cells with enhanced interfacial chemical stability

Mixed Sn-Pb perovskites are attracting significant attention due to their narrow bandgap and consequent potential for all-perovskite tandem solar cells. However, the conventional hole transport materials can lead to band misalignment or induce degradation at the buried interface of perovskite. Here we designed a self-assembled material 4-(9H-carbozol-9-yl)phenylboronic acid (4PBA) for the surface modification of the substrate as the hole-selective contact. It incorporates an electron-rich carbazole group and conjugated phenyl group, which contribute to a substantial interfacial dipole moment and tune the substrate's energy levels for better alignment with the Sn-Pb perovskite energy levels, thereby promoting hole extraction. Meanwhile, enhanced perovskite crystallization and improved contact at bottom of the perovskite minimized defects within perovskite bulk and at the buried interface, suppressing non-radiative recombination. Consequently, Sn-Pb perovskite solar cells using 4PBA achieved efficiencies of up to 23.45%. Remarkably, the 4PBA layer provided superior interfacial chemical stability, and effectively mitigated device degradation. Unencapsulated devices retained 93.5% of their initial efficiency after 2000 h of shelf storage.

Insights Into the Role of π-Electrons of Aromatic Aldehydes in Passivating Perovskite Defects

Carbonyl-containing aromatic ketones or aldehydes have been demonstrated to be effective defect passivators for perovskite films to improve performances of perovskite solar cells (PSCs). It has been claimed that both π-electrons within aromatic units and carbonyl groups can, separately, interact with ionic defects, which, however, causes troubles in understanding the passivation mechanism of those aromatic ketone/aldehyde molecules. Herein, we clarify the effect of both moieties in one molecule on the defect passivation by investigating three aromatic aldehydes with varied conjugation planes, namely, biphenyl-4-carbaldehyde (BPCA), naphthalene-2-carbaldehyde (NACA) and pyrene-1-carbaldehyde (PyCA). Our findings reveal that the π-electrons located in the conjugated system do not directly present strong passivation for defects, but enhance the electron cloud density of the carbonyl group augmenting its interaction with defect sites; thereby, with the extended conjugation plane of the three molecules, their defect passivation ability is gradually improved. PSCs incorporating PyCA with the most extended π-electrons delocalization achieve maximum power conversion efficiencies of 25.67 % (0.09 cm2) and 21.76 % (14.0 cm2). Moreover, these devices exhibit outstanding long-term stability, retaining 95 % of their initial efficiency after operation for 1000 hours at the maximum power point.

Enhanced coupling of perovskites with semiconductive properties by tuning multi-modal optically active nanostructured set-ups for photonics, photovoltaics and energy applications

This review describes the coupling of semiconducting materials with perovskites as main optically active elements for enhancing the performance depending on the optical set-up and coupling phenomena. The various uses of semiconductor nanoparticles and related nanomaterials for energy conduction and harvesting are discussed. Thus, it was obtained different materials highlighting the properties of perovskites incorporated within heterojunctions and hybrid nanomaterials where varied materials and sources were joined. Different multi-layered substrates are reported, and different strategies for improved electron and energy transfer and harvesting are elucidated Further, enhanced coupling of semiconductive properties for the above-mentioned processes is discussed. In this regard, various nanomaterials and their properties for improving energy applications such as solar cells are demonstrated. Moreover, the incorporation of plasmonic properties from different noble metal sources and pseudo-electromagnetic properties from graphene and carbon allotropes is discussed. Since variations in electromagnetic fields affect the semiconductive properties, it leads to varying effects and potential applications within the energy research field. Hence, this review could guide the development within energy research fields as nanophotonics, photovoltaics, and energy. This review is mainly focused on the development of solar energy cells by incorporating perovskites with varied hybrid nanomaterials, photonic materials, and metamaterials.

Mechanically Resilient and Highly Efficient Flexible Perovskite Solar Cells with Octylammonium Acetate for Surface Adhesion and Stress Relief

Flexible perovskite solar cells (FPSCs) have advanced significantly because of their excellent power-per-weight performance and affordable manufacturing costs. The unsatisfactory efficiency and mechanical stability of FPSCs are bottleneck challenges that limit their application. Here, we explore the use of octylammonium acetate (OAAc) with a long, intrinsic, flexible molecular chain on perovskite films for surface adhesion and mechanical releasing. The results showed that OAAc with high structural flexibility and strong molecular interactions can act as a mechanical release layer in releasing residual tensile stress, confirmed by the film and device characterizations as well as finite-element simulation. Moreover, the passivation of the OAAc could increase the formation energy of defects including I vacancy, Pb vacancy, and Pb-I antisite. The experimental results showed that the trap states of perovskites were significantly suppressed after OAAc modification, which is beneficial to the construction of high-quality films. With a high open-circuit voltage of 1.196 V, the efficiency of the OAAc-treated devices increased from 23.14% to 25.47% on a rigid substrate (23.12% on a flexible substrate), yielding superior long-term and mechanical durability. The corresponding flexible device retains 74% of the initial value even after 8000 bending cycles at a bending radius of 5 mm.

Formation Dynamics of Thermally Stable 1D/3D Perovskite Interfaces for High-Performance Photovoltaics

Direct understanding of the formation and crystallization of low-dimensional (LD) perovskites with varying dimensionalities employing the same bulky cations can offer insights into LD perovskites and their heterostructures with 3D perovskites. In this study, the secondary amine cation of N-methyl-1-(naphthalen-1-yl)methylammonium (M-NMA+) and the formation dynamics of its corresponding LD perovskite are investigated. The intermolecular π-π stacking of M-NMA+ and their connection with inorganic PbI6 octahedrons within the product structures control the formation of LD perovskite. In an N,N-dimethylformamide (DMF) precursor solution, both 1D and 2D products can be obtained. Interestingly, due to the strong interaction between M-NMA+ and the DMF solvent, compared to the 1D phase, the formation of 2D perovskites is uniquely dependent on heterogeneous nucleation. Nevertheless, post-treatment of 3D perovskite films with an isopropanol solution of M-NMAI leads to the exclusive formation of thermally stable 1D phases on the surface. The resulting 1D/3D heterostructure facilitates perovskite solar cells (PSCs) to not only achieve a record efficiency of 25.51% through 1D perovskite passivation but also significantly enhance the thermal stability of unencapsulated devices at 85 °C. This study deepens the understanding of the formation dynamics of LD perovskites and offers an efficient strategy for fabricating stable and high-performance PSCs.

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.

Improving Performance of Perovskite Solar Cells by Reducing Energetic Disorder of Hole Transport Polymer

Polymer hole transport materials offer significant efficiency and stability advantages for p-i-n perovskite solar cells. However, the energetic disorder of amorphous polymer hole transport materials not only limits carrier transport but also impedes contact between the polymer and perovskite, hindering the formation of high crystalline quality perovskites. Herein, a novel low energetic disordered polymer hole transport material, PF8ICz, featuring an indeno[3,2-b]carbazole unit with extended π-conjugation is designed and synthesized. Analyses based on both theoretical calculations and experimental validation highlight the advantages of PF8ICz as a low energetic disorder polymer hole transport material for perovskite solar cells, including improved carrier transport, enhanced perovskite affinity/passivation, and optimized energy levels. Perovskite films formed atop PF8ICz exhibit superior crystalline quality and improved exciton dynamics. PF8ICz-based perovskite solar cells achieve remarkable power efficiency (PCE > 25.4%) and outstanding stability (retaining 96.2% and 95.0% of their PCE under the ISOS-D-3 and ISOS-L-3 protocols over 1000 h, respectively). These findings underscore the importance of rational design of hole transport materials, contributing to the development of high-performance, stable perovskite solar cells for sustainable energy solutions.

Solvent-dripping modulated 3D/2D heterostructures for high-performance perovskite solar cells

The controlled growth of two-dimensional (2D) perovskite atop three-dimensional (3D) perovskite films reduces interfacial recombination and impedes ion migration, thus improving the performance and stability of perovskite solar cells (PSCs). Unfortunately, the random orientation of the spontaneously formed 2D phase atop the pre-deposited 3D perovskite film can deteriorate charge extraction owing to energetic disorder, limiting the maximum attainable efficiency and long-term stability of the PSCs. Here, we introduce a meta-amidinopyridine ligand and the solvent post-dripping step to generate a highly ordered 2D perovskite phase on the surface of a 3D perovskite film. The reconstructed 2D/3D perovskite interface exhibits reduced energetic disorder and yields cells with improved performance compared with control 2D/3D samples. PSCs fabricated with the meta-amidinopyridine-induced phase-pure 2D perovskite passivation show a maximum power conversion efficiency of 26.05% (a certified value of 25.44%). Under damp heat and outdoor tests, the encapsulated PSCs maintain 82% and 75% of their initial PCE after 1000 h and 840 h, respectively, demonstrating improved practical durability.

Ultraelastic Lead Halide Perovskite Films via Direct Laser Patterning

The precise patterning of elastic semiconductors holds encouraging prospects for unlocking functionalities and broadening the scope of optoelectronic applications. Here, perovskite films with notable elasticity capable of stretching over 250% are successfully fabricated by using a continuous-wave (CW) laser-patterning technique. Under CW laser irradiation, perovskite nanoparticles (NPs) undergo meticulous crystallization within the thermoplastic polyurethane (TPU) matrix, which yields the capability of an unparalleled stretch behavior. Furthermore, the strategic integration of β-phase poly(vinylidene fluoride) (β-PVDF) introduces a highly ordered dipolar framework, augmenting the crystallization dynamics of perovskite NPs during the laser-patterning process, thereby elevating the patterning efficiency and film quality. Furthermore, full-spectrum visible perovskite films that possess high transparency, high resolution, and adequate stability are achieved through the precise tuning of halide components, thereby emphasizing the impressive versatility of the high-elasticity printing technique. Our findings are meaningful for the direct patterning of high-precision, highly elastic semiconductors, finding a way for advancements in stretchable photonic and optoelectronic devices.

Asymmetric Modification of Carbazole Based Self-Assembled Monolayers by Hybrid Strategy for Inverted Perovskite Solar Cells

Carbazole-based self-assembled molecules (SAMs) are widely applied in inverted perovskite solar cells (iPSCs) due to their unique molecular properties. However, the symmetrical structure of the carbazole-based SAMs makes it difficult to finely regulate their performance, which impedes the further enhancement of the efficiency and stability of iPSCs. This work demonstrates that by constructing an asymmetric carbazole core, 9H-thieno[2',3' : 4,5]thieno[3,2-b]indole) (TTID), the key properties of SAM molecules can be effectively regulated. It has been confirmed that the hybrid thieno[2,3-b]thiophene unit of this asymmetric core governs the energy level, the surface wettability, and the defect passivation capability of the SAMs, while the substituent of core has a greater impact on the molecular dipole and device stability. The synergistic effects from thieno[2,3-b]thiophene and fluorine lead to the KF-derived iPSC demonstrating a certified power conversion efficiency (PCE) of 25.17 % and excellent operational stability. This hybrid design concept offers a promising approach for the further structural modification of SAMs in iPSCs.

Cross-Linkable Fullerene Electron Transport Layer with Internal Encapsulation Capability for Efficient and Stable Inverted Perovskite Solar Cells

A stable and compact fullerene electron transport layer (ETL) is crucial for high-performance inverted perovskite solar cells (PSCs). However, traditional fullerene-based ETLs like C60 and PCBM are prone to aggregate under operational conditions, a challenge recently recognized by academic and industrial researchers. Here, we designed and synthesized a novel cross-linkable fullerene molecule, bis((3-methyloxetan-3-yl)methyl) malonate-C60 monoadduct (BCM), for use as an ETL in PSCs. Upon a low-temperature annealing at 100 °C, BCM undergoes in situ cross-linking to form a robust cross-linked BCM (CBCM) film, which demonstrates excellent electron mobility and a suitable band structure for efficient PSCs. Our results show that PSCs incorporating CBCM-based ETL achieve an impressive efficiency of 25.89 % (certified: 25.36 %), significantly surpassing the 23.25 % efficiency of PCBM-based devices. The intramolecular covalent interactions within CBCM films effectively prevent aggregation and enhance film compactness, creating an internal encapsulation layer that mitigates the decomposition and ion migration of perovskite components. Consequently, CBCM-based PSCs show exceptional stability, maintaining 97.8 % of their initial efficiency after 1000 hours of maximum power point tracking, compared to only 78.6 % retention in PCBM-based devices after less than 820 hours.

Molecular ferroelectric self-assembled interlayer for efficient perovskite solar cells

The interfacial molecular dipole enhances the photovoltaic performance of perovskite solar cells (PSCs) by facilitating improved charge extraction. However, conventional self-assembled monolayers (SAMs) face challenges like inadequate interface coverage and weak dipole interactions. Herein, we develop a strategy using a self-assembled ferroelectric layer to modify the interfacial properties of PSCs. Specifically, we employ 1-adamantanamine hydroiodide (ADAI) to establish robust chemical interactions and create a dipole layer over the perovskite. The oriented molecular packing and spontaneous polarity of ferroelectric ADAI generate a substantial interfacial dipole, adjusting band bending at the anode, reducing band misalignment, and suppressing charge recombination. Consequently, our formamidinium lead iodide-based conventional PSC achieves efficiencies of 25.13% (0.06 cm2) and 23.5% (1.00 cm2) while exhibiting enhanced stability. Notably, we demonstrate an impressive efficiency of 25.59% (certified at 25.36%) in a 0.06 cm2 area for the inverted champion device, showcasing the promise of ferroelectric SAMs for PSCs performance enhancement.

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.

Nuclear Quadrupolar Resonance Structural Characterization of Halide Perovskites and Perovskitoids: A Roadmap from Electronic Structure Calculations for Lead-Iodide-Based Compounds

Metal halide perovskites, including some of their related perovskitoid structures, form a semiconductor class of their own, which is arousing ever-growing interest from the scientific community. With halides being involved in the various structural arrangements, namely, pure corner-sharing MX6 (M is metal and X is halide) octahedra, for perovskite networks, or alternatively a combination of corner-, edge-, and/or face-sharing for related perovskitoids, they represent the ideal probe for characterizing the way octahedra are linked together. Well known for their inherently large quadrupolar constants, which is detrimental to the resolution of nuclear magnetic resonance spectroscopy, most abundant halide isotopes (35/37Cl, 79/81Br, 127I) are in turn attractive for magnetic field-free nuclear quadrupolar resonance (NQR) spectroscopy. Here, we investigate the possibility of exploiting NQR spectroscopy of halides to distinctively characterize the various metal halide structural arrangements, using density functional theory simulations. Our calculations nicely match the available experimental results. Furthermore, they demonstrate that compounds with different connectivities of their MX6 building blocks, including lower dimensionalities such as 2D networks, show distinct NQR signals in a broad spectral window. They finally provide a roadmap of the characteristic NQR frequency ranges for each octahedral connectivity, which may be a useful guide to experimentalists, considering the long acquisition procedures typical of NQR. We hope this work will encourage the incorporation of NQR spectroscopy to further our knowledge of the structural diversity of metal halides.

Structurally Compact Penta(N,N-diphenylamino)corannulene as Dopant-free Hole Transport Materials for Stable and Efficient Perovskite Solar Cells

Hole transport materials (HTMs) are essential for improving the stability and efficiency of perovskite solar cells (PSCs). In this study, we have designed and synthesized a novel organic small molecule HTM, cor-(DPA)5, characterized by a bowl-shaped core with symmetric five diphenylamine groups. Compared to already-known HTMs, the bowl-shaped and relatively compact structure of cor-(DPA)5 facilitates intermolecular π-π interactions, promotes film formations, and enhances charge transport. Consequently, the cor-[DPA(2)]5 HTM exhibits high charge mobility, exceptional hydrophobicity, and a significantly elevated glass transition temperature. Superior to previously reported HTMs such as spiro-OMeTAD and cor-OMePTPA, our newly synthesized cor-(DPA)5 HTM is free from any ionic dopants. As a result, the dopant-free cor-[DPA(2)]5-based PSC demonstrates an impressive efficiency of 24.01 %, and exhibits outstanding operational stability. It retains 96 % after continuous exposure to 1 sun irradiation for 800 hours under MPP (maximum power point) tracking in ambient air. These findings present a structurally compact novel HTM and exemplify a new approach to the molecular design of HTM for the development of stable and effective PSCs.

Boosting Efficiency in Carbon Nanotube-Integrated Perovskite Photovoltaics

Carbon nanomaterials (graphene, carbon nanotubes, and graphene oxide) have potential applications for optoelectronics, thanks to their superior electronic and optical characteristics. The remarkable stability of carbon-based perovskite solar cells (PSCs) has attracted significant attention. Herein, a fluorine-doped carbon nanotube (F-CNT) is incorporated into the PSCs as a hole-transporting layer (HTL) in between methylammonium lead iodide (MAPbI3) and the rear electrode to develop an effective MAPbI3/HTL interface. The F-CNT bridges both the MAPbI3 film and the Au electrode and promotes photocarrier extraction and transportation between the two layers. The article presents a simulation-driven optimization approach for the development of efficient CNT-based PSCs. Many factors, such as the total defect density of the perovskite, the shallow acceptor density of the F-CNTs film thickness, the perovskite thickness, parasitic resistances, and temperature, have been studied using SCAPS-1D simulations. Utilizing the photovoltaic software SCAPS-1D, we simulated defect states and interfaces to approximate a realistic perovskite device in our analyses. The CNT-based PSC with an architecture of FTO/TiO2/MAPbI3/F-CNTs/Au achieved an outstanding power conversion efficiency (PCE) of 26.91%, with a fill factor (FF) of 84.23%.

Revealing the Dynamic Aspects of Photoinduced Halide Segregation in Mixed-Halide Cs0.15FA0.85PbI2Br Perovskite Films Using a Hyperspectral Imaging Technique

The band gap energy of halide perovskite semiconductors is manipulated by controlling the halide composition, and mixed halide perovskites are receiving much attention as top cell materials for tandem solar cells. To understand dynamic aspects of photoinduced halide segregation in mixed-halide perovskite films, we use a hyperspectral imaging technique. We reveal the space- and time-resolved photoluminescence (PL) spectra of Cs0.15FA0.85PbI2Br perovskite films during prolonged light illumination. Under applied electric fields, we observe photoinduced phase segregation at the excitation laser spot, with a line-shape I-rich region of low PL efficiency appearing near the anode electrode. This I-rich region moves from the anode to the cathode electrodes and stops at the laser excitation spot. We discuss the significant enhancement of halide ion migration under light illumination and the dynamical changes of photoinduced halide segregation.

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.

Unveiling Energy Conversion Mechanisms and Regulation Strategies in Perovskite Solar Cells

Despite recent revolutionary advancements in photovoltaic (PV) technology, further improving cell efficiencies toward their Shockley-Queisser (SQ) limits remains challenging due to inherent optical, electrical, and thermal losses. Currently, most research focuses on improving optical and electrical performance through maximizing spectral utilization and suppressing carrier recombination losses, while there is a serious lack of effective opto-electro-thermal coupled management, which, however, is crucial for further improving PV performance and the practical application of PV devices. In this article, the energy conversion and loss processes of a PV device (with a specific focus on perovskite solar cells) are detailed under both steady-state and transient processes through rigorous opto-electro-thermal coupling simulation. By innovatively coupling multi-physical behaviors of photon management, carrier/ion transport, and thermodynamics, it meticulously quantifies and analyzes energy losses across optical, electrical, and thermal domains, identifies heat components amenable to regulation, and proposes specific regulatory means, evaluates their impact on device efficiency and operating temperature, offering valuable insights to advance PV technology for practical applications.

Halogen-Bonded Hole-Transport Material Enhances Open-Circuit Voltage of Inverted Perovskite Solar Cells

Interfacial properties of a hole-transport material (HTM) and a perovskite layer are of high importance, which can influence the interfacial charge transfer dynamics as well as the growth of perovskite bulk crystals particularly in inverted structure. The halogen bonding (XB) has been recognized as a powerful functional group to be integrated with new small molecule HTMs. Herein, a carbazole-based halo (iodine)-functional HTM (O1), is synthesized for the first time, demonstrating a high hole mobility and suitable energy levels that align well with those of perovskites. The strong interaction between O1 and perovskite, i.e., I···I-, induces the formation of an ordered interlayer, which are verified by both theoretical and experimental studies. Compared to the reference HTM (O2) without any halo-function, the XB-induced interlayer effectively enhances the interfacial charge extraction efficiency, while significantly hindering the non-radiative charge recombination by reducing the surface traps upon the strong passivation effect. This is reflected as a big increase in the open-circuit voltage by up to 114 mV in the fabrication of inverted devices with the highest power conversion efficiency of 22.34%. Moreover, the ordered XB-driven interlayer at the interface of O1 and perovskite is mainly responsible for the extended lifespan under the operational conditions.

Progress of Hole-Transport Layers in Mixed Sn-Pb Perovskite Solar Cells

Hybrid organic-inorganic lead halide perovskite solar cells (PSCs) have rapidly emerged as a promising photovoltaic technology, with record efficiencies surpassing 26%, approaching the theoretical Shockley-Queisser limit. The advent of all-perovskite tandem solar cells (APTSCs), integrating Pb-based wide-bandgap (WBG) with mixed Sn-Pb narrow-bandgap (NBG) perovskites, presents a compelling pathway to surpass this limit. Despite recent innovations in hole transport layers (HTLs) that have significantly improved the efficiency and stability of lead-based PSCs, an effective HTL tailored for Sn-Pb NBG PSCs remains an unmet need. This review highlights the essential role of HTLs in enhancing the performance of Sn-Pb PSCs, focusing on their ability to mitigate non-radiative recombination and optimize the buried interface, thereby improving film quality. The distinct attributes of Sn-Pb perovskites, such as their lower energy levels and accelerated crystallization rates, necessitate HTLs with specialized properties. In this study, the latest advancements in HTLs are systematically examined for Sn-Pb PSCs, encompassing organic, self-assembled monolayer (SAM), inorganic materials, and HTL-free designs. The review critically assesses the inherent limitations of each HTL category, and finally proposes strategies to surmount these obstacles to reach higher device performance.

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.

Dual-Site Molecular Dipole Enables Tunable Interfacial Field Toward Efficient and Stable Perovskite Solar Cells

The interfacial management in perovskite solar cells (PSCs), including mitigating the carrier transport barrier and suppressing non-radiative recombination, still remains a significant challenge for efficiency and stability enhancement. Herein, by screening a family of fluorine (F) terminated dual-site organic dipole molecules, the study aims to gain insight into the molecular dipole array toward tunable interfacial field. Both experimental and theoretical results reveal that these functional interfacial dipole molecules can effectively anchor on perovskite surface through Lewis acid-base interaction. In addition, the tailored side-chain with terminated F atoms allows for altering and constructing a well matched perovskite/Spiro-OMeTAD interfacial contact. As a result, the inserting dual-site organic dipole array effectively modulates the interface to deliver a gradient energy level alignment, facilitating carrier extraction and transport. The optimal dual-site dipole trifluoro-methanesulfonamide mediated N-i-P PSCs achieve the highest efficiency of 25.47%, together with enhanced operational stability under 1000 h of the simulated 1-sun illumination exposure. These findings are believed to provide insight into the design of dual-site molecular dipole with sufficient interfacial tunability for perovskite-based optoelectronic devices.

Strain regulation retards natural operation decay of perovskite solar cells

Perovskite solar cells (pero-SCs) have undergone rapid development in the past decade. However, there is still a lack of systematic studies investigating whether the empirical rules of working lifetime assessment used for silicon solar cells can be applied to pero-SCs. It is believed that pero-SCs show enhanced stability under day/night cycling owing to the reported self-healing effect in the dark1,2. Here we find that the degradation of highly efficient FAPbI3 pero-SCs is much faster under a natural day/night cycling mode, bringing into question the widely accepted approach to estimate the operational lifetime of pero-SCs based on continuous-mode testing. We reveal the key factor to be the lattice strain caused by thermal expansion and shrinking of the perovskite during operation, an effect that gradually relaxes under the continuous-illumination mode but cycles synchronously under the cycling mode3,4. The periodic lattice strain under the cycling mode results in deep trap accumulation and chemical degradation during operation, decreasing the ion-migration potential and hence the device lifetime5. We introduce phenylselenenyl chloride to regulate the perovskite lattice strain during day/night cycling, achieving a certified efficiency of 26.3 per cent and a 10-fold improvement in the time required to reach 80% of peak efficiency (T80) under the cycling mode after the modification.

Enhanced Electric Field Minimizing Quasi-Fermi Level Splitting Deficit for High-Performance Tin-Lead Perovskite Solar Cells

The quasi-Fermi level splitting (QFLS) deficit caused by the non-radiative recombination at the interface of perovskite/electron transport layer (ETL) can lead to severe open-circuit voltage (VOC) loss and thus decreases the efficiency of perovskite solar cells (PSCs), however, has received limited attention in inverted tin-lead PSCs. Herein, the strategy of constructing an extra-electric field is presented by introducing ferroelectric polymer dipoles (FPD)-β-poly(1,1-difluoroethylene)-to suppress the QFLS deficit. The directional polarization of FPD can enhance the built-in electric field (BEF) and thus promote the charge transfer at the perovskite/ETL interface, which effectively suppresses non-radiative recombination. Furthermore, the incorporation of FPD facilitates high-quality crystallization of perovskite and reduces the surface energetic disorder. Therefore, the QFLS deficit in the perovskite/ETL half-stacked device is reduced from 62 to 27 meV after incorporating FPD, and the optimized device achieves an efficiency of 23.44% with a high VOC of 0.88 V. Additionally, the addition of FPD increases the activation energy for ion migration, which can reduce the effect of ion migration on the long-term stability of the device. Consequently, the FPD-incorporated device retains 88% of the initial efficiency after 1100 h of continuous illumination at the maximum power point (MPP).

Room-Temperature Ripening Enabled by Hygroscopic Salts for Hole-conductor-Free Printable Perovskite Solar Cells with Efficiency Over 20

Solution-processed perovskite films generally possess small grain sizes and high density of grain boundaries, which intensify non-radiative recombination of carriers and limit the power conversion efficiency (PCE) of solar cells. In this study, we report the room-temperature ripening enabled by the synergy of hygroscopic salts and moisture in air for efficient hole-conductor-free printable mesoscopic perovskite solar cells (p-MPSCs). Treating perovskite films with proper hygroscopic salts in damp air induces obvious secondary recrystallization, which coarsens the grains size from hundreds of nanometers to several micrometers. It's proposed that the hygroscopic salt at grain boundaries could absorb moisture and form a complex which could not only serve as mass transfer channel but also assist in the dissolution of perovskite grains. This activates mass transfer between small grains and large grains since they possess different solubilities, and thus ripens the perovskite film. Consequently, p-MPSCs treated with the hygroscopic salt of NH4SCN show an improved power conversion efficiency of 20.13 % from 17.94 %, and maintain >98 % of the initial efficiency under maximum power point tracking at 55±5 °C for 350 hours.

Long-term stability in perovskite solar cells through atomic layer deposition of tin oxide

Robust contact schemes that boost stability and simplify the production process are needed for perovskite solar cells (PSCs). We codeposited perovskite and hole-selective contact while protecting the perovskite to enable deposition of SnOx/Ag without the use of a fullerene. The SnOx, prepared through atomic layer deposition, serves as a durable inorganic electron transport layer. Tailoring the oxygen vacancy defects in the SnOx layer led to power conversion efficiencies (PCEs) of >25%. Our devices exhibit superior stability over conventional p-i-n PSCs, successfully meeting several benchmark stability tests. They retained >95% PCE after 2000 hours of continuous operation at their maximum power point under simulated AM1.5 illumination at 65°C. Additionally, they boast a certified T97 lifetime exceeding 1000 hours.

Molecular Structure Tailoring of Organic Spacers for High-Performance Ruddlesden-Popper Perovskite Solar Cells

Layer-structured Ruddlesden-Popper (RP) perovskites (RPPs) with decent stability have captured the imagination of the photovoltaic research community and bring hope for boosting the development of perovskite solar cell (PSC) technology. However, two-dimensional (2D) or quasi-2D RP PSCs are encountered with some challenges of the large exciton binding energy, blocked charge transport and poor film quality, which restrict their photovoltaic performance. Fortunately, these issues can be readily resolved by rationally designing spacer cations of RPPs. This review mainly focuses on how to design the molecular structures of organic spacers and aims to endow RPPs with outstanding photovoltaic applications. We firstly elucidated the important roles of organic spacers in impacting crystallization kinetics, charge transporting ability and stability of RPPs. Then we brought three aspects to attention for designing organic spacers. Finally, we presented the specific molecular structure design strategies for organic spacers of RPPs aiming to improve photovoltaic performance of RP PSCs. These proposed strategies in this review will provide new avenues to develop novel organic spacers for RPPs and advance the development of RPP photovoltaic technology for future applications.

Repeatable Perovskite Solar Cells through Fully Automated Spin-Coating and Quenching

Enhancing reproducibility, repeatability, as well as facilitating transferability between laboratories will accelerate the progress in many material domains, wherein perovskite-based optoelectronics are a prime use case. This study presents fully automated perovskite thin film processing using a commercial spin-coating robot in an inert atmosphere. We successfully apply this novel processing method to antisolvent quenching. This process is typically difficult to reproduce and transfer and is now enhanced to exceptional repeatability in comparison to manual processing. Champion perovskite solar cells demonstrate power conversion efficiencies as high as 19.9%, proving the transferability of established manual spin-coating processes to automatic setups. Comparison with human experts reveals that the performance is already on par, while automated processing yields improved homogeneity across the substrate surface. This work demonstrates that fully automated perovskite thin film processing improves repeatability. Such systems bear the potential to become a foundation for autonomous optimization and greatly improve transferability between laboratories.