Intermediate Phase Engineering with 2,2-Azodi(2-Methylbutyronitrile) for Efficient and Stable Perovskite Solar Cells

Synergistic Surface Reconstruction and Defect Passivation via Guanidine Sulfonate for High-Efficiency Perovskite Photovoltaics

Perovskite films have long suffered from various defects located at grain boundaries and surfaces (GBS), especially residual lead iodide (PbI2), which can seriously impair the photoelectric conversion efficiency (PCE) and long-term stability of the corresponding photovoltaic devices. Herein, guanidine sulfamate (GSM), with desired -NH2, S═O, and Gua+ functional groups, is introduced to the perovskite surface by a post-treatment process to achieve high-quality films with fewer defects. It was found that -NH2 and S═O in GSM contribute to the passivation of various defects in perovskites and suppress non-radiative recombination, thus improving the interfacial carrier transport efficiency. Meanwhile, the guanidine (Gua+) cations promote grain fusion during post-treatment to achieve large-sized grains and effectively reduce residual PbI2 content. Moreover, the optimized perovskite films also exhibited better energy level alignment and surface hydrophobicity. Consequently, the champion PCE of the optimized perovskite solar cells (PSCs) was increased from 21.69 to 23.85% at the appropriate GMS post-treatment concentration, along with a significant improvement in storage stability and light stability.

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.

Increase the Long-Wavelength Absorption for Carbon-Electrode Based Hole-Conductor-Free Perovskite Solar Cells by Thicker Perovskite Films

Weak reflectivity of carbon-electrode (CE) limits light harvesting of perovskite solar cells that are based on CEs (CPSCs), especially for long-wavelength region. To solve this problem, herein the crystallization of perovskite (PVSK) is regulated by tuning the concentration of PbI2 precursor during the two-step growth method. As concentration increases from 1.0 to 1.7 mol L-1, film thickness of PVSK rises from ≈360 to ≈850 nm, and the average grain/crystallite size of PVSK enlarges from 0.70 to 1.14 µm, and from 54.2 to 67.5 nm, respectively. Due to the upgraded crystallization, Urbach energy drops from 98 to 41 meV, lifetime of charge carriers increases obviously, meanwhile the light harvesting of PVSK is improved during the long-wavelength regions (600-810 nm). External quantum efficiency test on the CPSCs shows that the integrated short circuit current density (JSC) increases by 15.6% during the long-wavelength region. Accordingly, JSC improves from 20.27 (±0.36) to 22.58 (±0.27) mA cm-2. Besides, leakage is retarded, and open-circuit voltage is improved. These merits help elevate the power conversion efficiency from 15.37 (±0.42) to 16.37 (±0.68) % (optimized at 17.69%). Prolonging spin-time of PbI2 further improves PVSK crystallization and light harvest, which optimizes device efficiency to 19.17%.

Meticulous Design of High-Polarity Interface Material for FACsPbI3 Perovskite Solar Cells with Efficiency of 26.47

Designing new interface materials with the multifunctions of upper film crystallization control, interfacial defects passivation, and interfacial energy level regulation is crucial for developing efficient and stable perovskite solar cells (PSCs). Herein, a high polarity interfacial material, 2-cyano-N,N,N-trimethylammonium bromide (CNCB), was synthesized to engineer the buried interface between SnO2 and perovskite of the PSCs. Comprehensive theoretical and experimental investigations demonstrate that CNCB interacts with perovskite precursors (PbI2 and FAI) to regulate crystallization kinetics, yielding perovskite films with preferred orientation and reduced defects. Simultaneously, CNCB chemically interacts with both SnO2 and perovskite surfaces, effectively passivating oxygen vacancies in SnO2 and undercoordinated Pb2⁺ defects at the perovskite buried surface. Furthermore, the high dipole moment of CNCB induces beneficial interfacial polarization, optimizing energy level alignment and suppressing non-radiative recombination. The CNCB-modified FACsPbI3 PSCs achieve a champion power conversion efficiency (PCE) of 26.47% with exceptional operational stability, retaining 87.14% of their initial efficiency after 1000 h of continuous 1-sun illumination. This work establishes a molecular design paradigm for multifunctional interfacial materials in perovskite optoelectronics, highlighting the synergistic roles of crystallization control, defect passivation, and dipole engineering in high-performance devices.

PTAA-Based Perovskite Photovoltaics Catching up: Ionic Liquid Engineering-Assisted Crystallization Through Sequential Deposition

PTAA as a widely studied polymeric hole transporting material, has garnered significant attention due to its outstanding thermal and chemical stability. However, the performance of PTAA-based p-i-n devices is shown to lag behind counterpart utilizing oxides or SAMs. In this study, the ionic liquid, 1-ethyl-3-methylimidazolium formate (EMIMCOOH), is innovatively introduced into the lead iodide (PbI2) precursor solution, resulting in a more pronounced mesoporous PbI2 film with expended pore-size and denser pores. This enhancement is attributed to the coordination bond between the ─C═O group in EMIMCOOH and Pb2+. This intensified mesoporous morphology not only facilities the reaction between PbI2 and the organic layer, but also promotes the PbI2 conversion into perovskite material. Importantly, the incorporation of EMIMCOOH slows down the perovskite conversion process, increasing perovskite domain size and suppressed Pb0 trap density, resulting in a uniform perovskite layer with enhanced charge transport properties, as evidenced by the conducting atomic force microscope (c-AFM) results. As a result, the incorporation of EMIMCOOH yields a power conversion efficiency (PCE) of 24.10% and a high fill factor exceeding 85%. Notably, the PCE of the EMIMCOOH-modified device can still maintain 86% of the initial value after 1500 h at 25 °C in an N2 atmosphere.

Tailoring Crystal Growth Regulation and Dual Passivation for Air-Processed Efficient Perovskite Solar Cells

Hybrid metal halide perovskite solar cells (PSCs) are emerging as highly competitive next-generation photovoltaics due to their excellent performance and low production cost. However, the construction of high-efficiency PSCs typically requires an inert nitrogen environment within a glove box, inadvertently increasing manufacturing costs and hindering the transition from lab-scale to industrial-scale production. In this work, an air ambient fabrication of pure α-phase FAPbI3 PSCs with high-efficiency and stability, utilizing a dual-functional engineering strategy assisted by 3-Guanidinopropionicacid (3-GuA) is reported. 3-GuA assists in managing excess PbI2 and promotes the formation of high-quality FAPbI3 films via intermolecular exchange. Simultaneously, the existence of 3-GuA minimizes the defects and stabilizes the resulting perovskite films. As a result, the ambient-air fabricated PSCs achieve a power conversion efficiency (PCE) of 24.2% with negligible hysteresis and excellent stability. Additionally, these devices demonstrate superior reproducibility, offering valuable guidance for future advancements in this technology.

Targeted Anchoring of All Cations with 5-Bromopyridine-3-sulfonic Acid for High-Performance Perovskite Solar Cells

The quality of organic-inorganic hybrid perovskite films directly affects the application prospect of perovskite solar cells (PSCs), where organic and inorganic cations are the core elements that affect the quality of the perovskite. The additive strategy has been widely used to passivate cation-related defects in perovskite films. Here, the perovskite precursor solution introduced 5-bromopyridine-3-sulfonic acid (BOH) with a potential all-cation passivation function. The experimental results verified that the N atom on pyridine in the BOH molecular structure passivated the defects in perovskite by binding with undercoordination Pb2+, and the sulfonic acid group inhibited nonradiative recombination through their interactions with FA+ and Pb2+, improving perovskite grain size and crystallinity, and enhancing film quality. Thanks to the all-cationic targeted anchoring effect of BOH, the efficiency of the BOH-treated device upgraded from 22.32 to 24.33%. Importantly, PSCs with BOH showed excellent stability after exposure to 25% humidity for 1200 h at room temperature.

Constructing bottom-up n-p perovskite homojunctions for enhanced performance of electron transport layer-free solar cells

We constructed the high-quality perovskite films with bottom-up n-p homojunctions via a modified sequential two-step deposition technique, which optimized the energy level alignment between the perovskite layer and the adjacent contacts for promoting charge separation and extraction, as well as suppressing non-radiative recombination. The resultant n-p homojunction-based electron transport layer-free perovskite solar cells achieved improved efficiency, which was ∼13% higher than that of the control counterpart.

Tin-Lead Perovskite Solar Cells with Preferred Crystal Orientation by Buried Interface Approach

Mixed tin-lead perovskite solar cells (PSCs) have garnered much attention for their ideal bandgap and high environmental research value. However, poly (3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS), widely used as a hole transport layer (HTL) for Sn-Pb PSCs, results in unsatisfactory power conversion efficiency (PCE) and long-term stability of PSCs due to its acidity and moisture absorption. A synergistic strategy by incorporating histidine (HIS) into the PEDOT: PSS HTL is applied to simultaneously regulate the nucleation and crystallization of perovskite (PVK). HIS neutralizes the acidity of PEDOT: PSS and enhances conductivity. Especially, the coordination of the C═N and -COO- functional groups in the HIS molecule with Sn2+ and Pb2+ induces vertical growth of PVK film, resulting in the release of residual surface stress. Additionally, this strategy also optimizes the energy level alignment between the perovskite layer and the HTL, which improves charge extraction and transport. With these cooperative effects, the PCE of Sn-Pb PSCs reaches 21.46% (1 sun, AM1.5), maintaining excellent stability under a nitrogen atmosphere. Hence, the buried interface approach exhibits the potential for achieving high-performance and stable Sn-Pb PSCs.

Achievements, challenges, and future prospects for industrialization of perovskite solar cells

In just over a decade, certified single-junction perovskite solar cells (PSCs) boast an impressive power conversion efficiency (PCE) of 26.1%. Such outstanding performance makes it highly viable for further development. Here, we have meticulously outlined challenges that arose during the industrialization of PSCs and proposed their corresponding solutions based on extensive research. We discussed the main challenges in this field including technological limitations, multi-scenario applications, sustainable development, etc. Mature photovoltaic solutions provide the perovskite community with invaluable insights for overcoming the challenges of industrialization. In the upcoming stages of PSCs advancement, it has become evident that addressing the challenges concerning long-term stability and sustainability is paramount. In this manner, we can facilitate a more effective integration of PSCs into our daily lives.

Stable Inverted Perovskite Solar Cells with Efficiency over 23.0% via Dual-Layer SnO2 on Perovskite

Perovskite solar cells (PSCs) have shown great potential for reducing costs and improving power conversion efficiency (PCE). One effective method to achieve the latter is to use an all-inorganic charge transport layer (ICTL). However, traditional methods for crystallizing inorganic layers often result in the formation of a powder instead of a continuous film. To address this issue, we designed a dual-layer inorganic electron transport layer (IETL). This dual-layer structure consists of a layer of SnO2 nanocrystals (SnO2 NCs) deposited via a solution process and a dense SnO2 layer deposited through atomic layer deposition (ALD SnO2) to fill the cracks and gaps between the SnO2 NCs. PSCs having these dual-layer SnO2 ETLs achieved a high efficiency of 23.0%. This efficiency surpasses the recorded performance of ICTLs deposited on the perovskite. Furthermore, the PCE is comparable to that achieved with a C60 ETL. Moreover, the high-density structure of the ALD SnO2 layer inhibits the vertical migration of ions, resulting in improved thermal stability. After continuous heating at 85 °C in 10% humidity for 1000 h, the PCE of the dual-layer SnO2 structure decreased by 18%, whereas that of the C60/BCP structure decreased by 36%. The integration of dual-layer SnO2 into PSCs represents a significant advancement in achieving high-performance, commercially viable inverted monolithic PSCs or tandem solar cells.

Room Temperature Ionic Liquid Capping Layer for High Efficiency FAPbI3 Perovskite Solar Cells with Long-Term Stability

Ionic liquid salts (ILs) are generally recognized as additives in perovskite precursor solutions to enhance the efficiency and stability of solar cells. However, the success of ILs incorporation as additives is highly dependent on the precursor formulation and perovskite crystallization process, posing challenges for industrial-scale implementation. In this study, a room-temperature spin-coated IL, n-butylamine acetate (BAAc), is identified as an ideal passivation agent for formamidinium lead iodide (FAPbI3) films. Compared with other passivation methods, the room-temperature BAAc capping layer (BAAc RT) demonstrates more uniform and thorough passivation of surface defects in the FAPbI3 perovskite. Additionally, it provides better energy level alignment for hole extraction. As a result, the champion n-i-p perovskite solar cell with a BAAc capping layer exhibits a power conversion efficiency (PCE) of 24.76%, with an open-circuit voltage (Voc) of 1.19 V, and a Voc loss of ≈330 mV. The PCE of the perovskite mini-module with BAAc RT reaches 20.47%, showcasing the effectiveness and viability of this method for manufacturing large-area perovskite solar cells. Moreover, the BAAc passivation layer also improves the long-term stability of unencapsulated FAPbI3 perovskite solar cells, enabling a T80 lifetime of  3500 h when stored at 35% relative humidity at room temperature in an air atmosphere.

Manipulating Crystal Growth and Secondary Phase PbI2 to Enable Efficient and Stable Perovskite Solar Cells with Natural Additives

In perovskite solar cells (PSCs), the inherent defects of perovskite film and the random distribution of excess lead iodide (PbI2) prevent the improvement of efficiency and stability. Herein, natural cellulose is used as the raw material to design a series of cellulose derivatives for perovskite crystallization engineering. The cationic cellulose derivative C-Im-CN with cyano-imidazolium (Im-CN) cation and chloride anion prominently promotes the crystallization process, grain growth, and directional orientation of perovskite. Meanwhile, excess PbI2 is transferred to the surface of perovskite grains or formed plate-like crystallites in local domains. These effects result in suppressing defect formation, decreasing grain boundaries, enhancing carrier extraction, inhibiting non-radiative recombination, and dramatically prolonging carrier lifetimes. Thus, the PSCs exhibit a high power conversion efficiency of 24.71%. Moreover, C-Im-CN has multiple interaction sites and polymer skeleton, so the unencapsulated PSCs maintain above 91.3% of their initial efficiencies after 3000 h of continuous operation in a conventional air atmosphere and have good stability under high humidity conditions. The utilization of biopolymers with excellent structure-designability to manage the perovskite opens a state-of-the-art avenue for manufacturing and improving PSCs.

Polyvinyl Pyrrolidone Induced "Confinement Effect" on PbI2 and the Improvement on Crystallization and Thermal Stability of Perovskite

Polyvinyl pyrrolidone is blended in PbI2 with varied concentration, so as to study the coarsening dynamics of perovskite during the two-step growth method. It is observed that polyvinyl pyrrolidone hinders the crystallization of PbI2 and helps to form a more amorphous PbI2 matrix, which then improves perovskite crystallization. As the blending concentration increases from 0 to 2 mM, average crystallite/grain size of perovskite increases from 40.29 nm/0.79 µm to 84.35 nm/1.02 µm while surface fluctuation decreases slightly from 25.64 to 23.96 nm. The observations are caused by the "confinement effect" brought by polyvinyl pyrrolidone on PbI2 . Elevating blending concentration of polyvinyl pyrrolidone results in smaller PbI2 crystallites and more amorphous PbI2 matrix, thus reducing the diffusion/reaction barrier between PbI2 and organic salt and favoring perovskite crystallization. As blending concentration increases from 0 to 2 mM, the device efficiency rises from 19.76 (± 0.60) % to 20.50 (± 0.89) %, with the optimized value up to 22.05%, which is further improved to 24.48% after n-Octylammonium iodide (OAI)-basing surface modification. The study enlarges the scope of "confinement effect" brought by polymer molecules, which is beneficial for efficient and stable perovskite solar cell fabrication.

Regulating Crystal Orientation via Ligand Anchoring Enables Efficient Wide-Bandgap Perovskite Solar Cells and Tandems

Wide-bandgap (WBG) perovskite solar cells have attracted considerable interest for their potential applications in tandem solar cells. However, the predominant obstacles impeding their widespread adoption are substantial open-circuit voltage (VOC ) deficit and severe photo-induced halide segregation. To tackle these challenges, a crystal orientation regulation strategy by introducing dodecyl-benzene-sulfonic-acid as an additive in perovskite precursors is proposed. This method significantly promotes the desired crystal orientation, passivates defects, and mitigates photo-induced halide phase segregation in perovskite films, leading to substantially reduced nonradiative recombination, minimized VOC deficits, and enhanced operational stability of the devices. The resulting 1.66 eV bandgap methylamine-free perovskite solar cells achieve a remarkable power conversion efficiency (PCE) of 22.40% (certified at 21.97%), with the smallest VOC deficit recorded at 0.39 V. Furthermore, the fabricated semitransparent WBG devices exhibit a competitive PCE of 20.13%. Consequently, four-terminal tandem cells comprising WBG perovskite top cells and 1.25 eV bandgap perovskite bottom cells showcase an impressive PCE of 28.06% (stabilized 27.92%), demonstrating great potential for efficient multijunction tandem solar cell applications.

Dual-Interface Engineering in Perovskite Solar Cells with 2D Carbides

Passivating the interfaces between the perovskite and charge transport layers is crucial for enhancing the power conversion efficiency (PCE) and stability in perovskite solar cells (PSCs). Here we report a dual-interface engineering approach to improving the performance of FA0.85 MA0.15 Pb(I0.95 Br0.05 )3 -based PSCs by incorporating Ti3 C2 Clx Nano-MXene and o-TB-GDY nanographdiyne (NanoGDY) into the electron transport layer (ETL)/perovskite and perovskite/ hole transport layer (HTL) interfaces, respectively. The dual-interface passivation simultaneously suppresses non-radiative recombination and promotes carrier extraction by forming the Pb-Cl chemical bond and strong coordination of π-electron conjugation with undercoordinated Pb defects. The resulting perovskite film has an ultralong carrier lifetime exceeding 10 μs and an enlarged crystal size exceeding 2.5 μm. A maximum PCE of 24.86 % is realized, with an open-circuit voltage of 1.20 V. Unencapsulated cells retain 92 % of their initial efficiency after 1464 hours in ambient air and 80 % after 1002 hours of thermal stability test at 85 °C.