Stabilizing perovskite-substrate interfaces for high-performance perovskite modules

Improving Perovskite Solar Cell Performance and Stability via Thermal Imprinting-Assisted Ion Exchange Passivation

The latest development in perovskite solar cell (PSC) technology has been significantly influenced by advanced techniques aimed at passivating surface defects. This work presents a new approach called thermal imprinting-assisted ion exchange passivation (TIAIEP), which delivers a different approach to conventional solution-based methods. TIAIEP focuses on addressing surface imperfections in solid-state films by using a passivator that promotes ion exchange specifically at the defect sites within the perovskite layer. By adjusting the time and temperature of the TIAIEP process, we achieve substantial enhancement in the creation of a compositional gradient within the films. This optimization slows the cooling rate of hot carriers, leading to minimizing charge recombination and improving the device performance. Remarkably, devices treated with TIAIEP achieve a 22.29% power conversion efficiency and show outstanding stability, with unencapsulated PSCs maintaining 91% of their original efficiency after over 2000 h of storage and 90% efficiency after 1200 h of constant illumination. These results highlight TIAIEP's effectiveness in mitigating surface defects, improving both the photoelectric and stability performance of PSCs, and indicating significant potential for large-scale application in perovskite film passivation, promoting the widespread adoption of this technology.

Buried Interface Strategies with Covalent Organic Frameworks for High-Performance Inverted Perovskite Solar Cells

Simultaneously controlling defects and film morphology at the buried interface is a promising approach to improve the power conversion efficiency (PCE) of inverted perovskite solar cells (PSCs). Here, two new donor‒acceptor type semiconductive covalent organic frameworks (COFs) are developed, COFTPA and COFICZ. The carefully designed COFs structure not only effectively regulates the morphology and defects of the buried interface film, but also realizes the alignment with the energy level of the perovskite film and enhances the extraction and transmission of the interface charge. Among them, COFICZ-treated inverted PSCs achieved a maxmum PCE of 25.68% (certified 25.14%), the inverted PCE reached a minimum PCE of 22.92% for 1 cm2 device. The efficiency of inverted PSCs with a 1.68 eV wide bandgap reached 22.92%, which is the highest datum of the reported 1.68 eV wide bandgap PSC. This lays the groundwork for the commercialization of perovskite/silicon tandem solar cells. Additionally, the unencapsulated devices demonstrated a high degree of stability during operational use and when subjected to conditions of high humidity and temperature.

Reconstruction and Solidification of Dion-Jacobson Perovskite Top and Buried Interfaces for Efficient and Stable Solar Cells

Quasi-two-dimensional (Q-2D) perovskites show great potential in the field of photonic and optoelectronic device applications. However, defects and local lattice dislocation still limit performance and stability improvement by nonradiative recombination, unpreferred phase distribution, and unbonded amines. Here, a low-temperature synergistic strategy for both reconstructing and solidifying the perovskite top and buried interface is developed. By post-treating the 1,4-phenylenedimethanammonium (PDMA) based (PDMA)MA4Pb5I16 films with cesium acetate (CsAc) before thermal annealing, a condensation reaction between R-COO- and -NH2 and ion exchange between Cs+ and MA+ occur. It converts the unbonded amines to amides and passivates uncoordinated Pb2+. Meanwhile, it adjusts film composition and improves the phase distribution without changing the out-of-plane grain orientation. Consequently, performance of 18.1% and much-enhanced stability (e.g., stability for photo-oxygen increased over 10 times, light-thermal for T90 over 4 times, and reverse bias over 3 times) of (PDMA)MA4Pb5I16 perovskite solar cells are demonstrated.

Synergistic Buried Interface Regulation of Tin-Lead Perovskite Solar Cells via Co-Self-Assembled Monolayers

Tin-lead (Sn-Pb) perovskite solar cells (PSCs) hold considerable potential for achieving efficiencies near the Shockley-Queisser (S-Q) limit. Notably, the inverted structure stands as the preferred fabrication method for the most efficient Sn-Pb PSCs. In this regard, it is imperative to implement a strategic customization of the hole selective layer to facilitate carrier extraction and refine the quality of perovskite films, which requires effective hole selectivity and favorable interactions with Sn-Pb perovskites. Herein, we propose the development of Co-Self-Assembled Monolayers (Co-SAM) by integrating both [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) and glycine at the buried contacts. The one-step deposition process employed in the fabrication of the Co-SAM ensures uniform coverage, resulting in a homogeneous surface potential. This is attributed to the molecular interactions occurring between 2PACz and glycine in the processing solution. Furthermore, the amine (-NH2) and ammonium (-NH3+) groups in glycine effectively passivate Sn4+ defects at the buried interface of Sn-Pb perovskite films, even under thermal stress. Consequently, the synergistic buried interface regulation of Co-SAM leads to a power conversion efficiency (PCE) of 23.46%, which outperforms devices modified with 2PACz or glycine alone. The Co-SAM-modified Sn-Pb PSC demonstrates enhanced thermal stability, maintaining 88% of its initial PCE under 65 °C thermal stress for 590 h.

The Promise and Challenges of Inverted Perovskite Solar Cells

Recently, there has been an extensive focus on inverted perovskite solar cells (PSCs) with a p-i-n architecture due to their attractive advantages, such as exceptional stability, high efficiency, low cost, low-temperature processing, and compatibility with tandem architectures, leading to a surge in their development. Single-junction and perovskite-silicon tandem solar cells (TSCs) with an inverted architecture have achieved certified PCEs of 26.15% and 33.9% respectively, showing great promise for commercial applications. To expedite real-world applications, it is crucial to investigate the key challenges for further performance enhancement. We first introduce representative methods, such as composition engineering, additive engineering, solvent engineering, processing engineering, innovation of charge transporting layers, and interface engineering, for fabricating high-efficiency and stable inverted PSCs. We then delve into the reasons behind the excellent stability of inverted PSCs. Subsequently, we review recent advances in TSCs with inverted PSCs, including perovskite-Si TSCs, all-perovskite TSCs, and perovskite-organic TSCs. To achieve final commercial deployment, we present efforts related to scaling up, harvesting indoor light, economic assessment, and reducing environmental impacts. Lastly, we discuss the potential and challenges of inverted PSCs in the future.

NJmat: Data-Driven Machine Learning Interface to Accelerate Material Design

Machine learning techniques have significantly transformed the way materials scientists conduct research. However, the widespread deployment of machine learning software in daily experimental and simulation research for materials and chemical design has been limited. This is partly due to the substantial time investment and learning curve associated with mastering the necessary codes and computational environments. In this paper, we introduce a user-friendly, data-driven machine learning interface featuring multiple "button-clicking" functionalities to streamline the design of materials and chemicals. This interface automates the processes of transforming materials and molecules, performing feature selection, constructing machine learning models, making virtual predictions, and visualizing results. Such automation accelerates materials prediction and analysis in the inverse design process, aligning with the time criteria outlined by the Materials Genome Initiative. With simple button clicks, researchers can build machine learning models and predict new materials once they have gathered experimental or simulation data. Beyond the ease of use, NJmat offers three additional features for data-driven materials design: (1) automatic feature generation for both inorganic materials (from chemical formulas) and organic molecules (from SMILES), (2) automatic generation of Shapley plots, and (3) automatic construction of "white-box" genetic models and decision trees to provide scientific insights. We present case studies on surface design for halide perovskite materials encompassing both inorganic and organic species. These case studies illustrate general machine learning models for virtual predictions as well as the automatic featurization and Shapley/genetic model construction capabilities. We anticipate that this software tool will expedite materials and molecular design within the scope of the Materials Genome Initiative, particularly benefiting experimentalists.

Towards High-Performance Inverted Mesoporous Perovskite Solar Cell by Using Bathocuproine (BCP)

Perovskite solar cells (PSCs) are considered the most promising photovoltaic devices to replace silicon-based solar cells because of their low preparation cost and high photoelectric conversion efficiency (PCE). Reducing defects in perovskite films is an effective means to improve the efficiency of PSCs. In this paper, a lead chelator was selected and mixed into hole transport layers (HTLs) to design and prepare mesoporous PSCs with the structure of ITO/PTAA(BCP)/Al2O3/PVK/PCBM/BCP/Ag, and its modification effect on the buried interface at the bottom of the perovskite layer in the mesoporous structure was explored. The experimental results show that in the presence of mesoporous alumina, the lead chelator can still play a role in modifying the bottom of the perovskite film. The use of lead chelator as passivation material added to the HTL can effectively reduce the residue of dimethyl sulfoxide (DMSO) and decrease the defects at the bottom of the perovskite film, which dramatically improves the device performance. The PCE of the device is increased from 18.03% to 20.78%, which is an increase of 15%. The work in this paper provides an effective method to enhance the performance of PSCs.

In Situ PL Probes the Effect of 2D SnSe Nanosheets on the Crystallization Process of CsPbI2Br Perovskite Solar Cells

Reducing defects in the active layer is important for improving the crystalline quality of all-inorganic perovskite solar cells (PSCs). Exploring novel additives is one of the most promising approaches to minimize active layer defects. In this work, two-dimensional (2D) SnSe nanosheets with excellent optoelectronic properties are prepared using an ultrasonic exfoliation method. The prepared 2D SnSe nanosheets are introduced into a CsPbI2Br precursor, which reduces the defect formation at grain boundaries and enhances the crystallinity of CsPbI2Br perovskites. We use the in situ photoluminescence (PL) technique to investigate the role of 2D materials in the crystallization process. The results show that SnSe nanosheets primarily shorten the grain boundary merging time and reduce the defect generation during the grain boundary merging stage, thereby regulating the crystallization of perovskite. In addition, SnSe nanosheets passivate uncoordinated Pb atoms at grain boundaries by Se atoms, further reducing the defect density in perovskite. As a result, PSCs exhibit a higher power conversion efficiency (PCE) of 14.24% and a Voc of 1.22 V. This study highlights the role of 2D materials in enhancing the crystalline quality and PCE of PSCs.

High-Efficiency Inverted Perovskite Solar Cells via In Situ Passivation Directed Crystallization

Lead halide perovskite solar cells (PSCs) have emerged as one of the influential photovoltaic technologies with promising cost-effectiveness. Though with mild processabilities to massive production, inverted PSCs have long suffered from inferior photovoltaic performances due to intractable defective states at boundaries and interfaces. Herein, an in situ passivation (ISP) method is presented to effectively adjust crystal growth kinetics and obtain the well-orientated perovskite films with the passivated boundaries and interfaces, successfully enabled the new access of high-performance inverted PSCs. The study unravels that the strong yet anisotropic ISP additive adsorption between different facets and the accompanied additive engineering yield the high-quality (111)-orientated perovskite crystallites with superior photovoltaic properties. The ISP-derived inverted perovskite solar cells (PSCs) have achieved remarkable power conversion efficiencies (PCEs) of 26.7% (certified as 26.09% at a 5.97 mm2 active area) and 24.5% (certified as 23.53% at a 1.28 cm2 active area), along with decent operational stabilities.

Suppressing interfacial nucleation competition through supersaturation regulation for enhanced perovskite film quality and scalability

The growing interest in cost-effective and high-performing perovskite solar cells (PSCs) has driven extensive research. However, the challenge lies in upscaling PSCs while maintaining high performance. This study focuses on achieving uniform and compact perovskite films without pinholes and interfacial voids during upscaling from small PSCs to large-area modules. Competition in nucleation at concavities with various angles on rough-textured substrates during the gas-pumping drying process, coupled with different drying rates across the expansive film, aggravates these issues. Consequently, substrate roughness notably influences the deposition window of compact large-area perovskite films. We propose a supersaturation regulation approach aimed at achieving compact deposition of high-quality perovskite films over large areas. This involves introducing a rapid drying strategy to induce a high-supersaturation state, thereby equalizing nucleation across diverse concavities. This breakthrough enables the production of perovskite photovoltaics with high efficiencies of 25.58, 21.86, and 20.62% with aperture areas of 0.06, 29, and 1160 square centimeters, respectively.

Efficient and stable perovskite mini-module via high-quality homogeneous perovskite crystallization and improved interconnect

The efficiency and stability of perovskite module devices are mainly limited by the quality of scalable perovskite films and sub-cells' lateral contact. Here, firstly, we report constant low temperature substrate to regulate the growth of perovskite intermediate films to slow down the crystallization for obtaining high-quality homogeneous perovskite films in large scale size, which avoid the effect of the ambient temperature on the film quality. Secondly, a scribing step named P1.5 was added before the top function layers deposition, the diffusion barrier layer can be formed "naturally" at the interconnection interface without introducing any additional materials, which well alleviates the diffusion degradation process. As a result, our inverted perovskite devices exhibit a very small efficiency loss with area expansion comparable to other photovoltaic devices (for example, Cadmium Telluride), the perovskite module (aperture area 14.61 cm2) shows a certified quasi-steady-state power conversion efficiency of 22.73%, and the module maintaining over 90% of its initial efficiency after 1000 hours of continuous operation under illumination.

An Equalized Flow Velocity Strategy for Perovskite Colloidal Particles in Flexible Perovskite Solar Cells

The non-uniform distribution of colloidal particles in perovskite precursor results in an imbalanced response to the shear force during flexible printing process. Herein, it is observed that the continuous disordered migration occurring in perovskite inks significantly contributes to the enlargement of colloidal particles size and diminishes the crystallization activity of the inks. Therefore, a molecular encapsulation architecture by glycerol monostearate to mitigate colloidal particles collisions in the precursor ink, while simultaneously homogenizing the size distribution of perovskite colloids to minimize their diffusion disparities, is devised. The utilization of colloidal particles with a molecular encapsulation structure enables the achievement of uniform deposition during the printing process, thereby effectively balancing the crystallization rate and phase transition in the film and facilitating homogeneous crystallization of perovskite films. The large-area flexible perovskite device (1.01 cm2 and 100 cm2) fabricated through printing processes, achieves an efficiency of 24.45% and 15.87%, respectively, and manifests superior environmental stability, maintaining an initial efficiency of 91% after being stored in atmospheric ambiences for 150 days (unencapsulated). This work demonstrates that the dynamic evolution process of colloidal particles in both the precursor ink and printing process represents a crucial stride toward achieving uniform crystallization of perovskite films.

Air-Processed Perovskite Solar Cells with >25% Efficiency and High Stability Enabled by Crystallization Modulation and Holistic Passivation

Organic semiconductors (e.g., PCBM and IDIC) frequently serve as interface passivants for perovskite solar cells (PSCs) due to their beneficial passivation effects on perovskite interfaces. However, their passivation to the interiors of perovskite films is greatly limited by their poor solubility in polar solvents and compatibility issues. Here the facile synthesis of organic semiconductor nanoparticle (NP) passivants that readily disperse in perovskite inks is reported. Adding these NPs into perovskite inks not only modulates perovskite crystallization, improves film quality and conductivity, but also achieves holistic bulk film passivation. Consequently, blade-coated p-i-n PSCs with ICBA NPs achieve an impressive efficiency of 25.1% (independently certified as 25.0%), the highest reported value for air-processed PSCs irrespective of fabrication methods or device structures. This work develops a novel approach for effective and holistic perovskite passivation by converting conventional passivants to perovskite-compatible NPs, paving the way for more efficient and stable perovskite solar devices.

Buried interface molecular hybrid for inverted perovskite solar cells

Perovskite solar cells with an inverted architecture provide a key pathway for commercializing this emerging photovoltaic technology because of the better power conversion efficiency and operational stability compared with the normal device structure. Specifically, power conversion efficiencies of the inverted perovskite solar cells have exceeded 25% owing to the development of improved self-assembled molecules1-5 and passivation strategies6-8. However, poor wettability and agglomeration of self-assembled molecules9-12 cause interfacial losses, impeding further improvement in the power conversion efficiency and stability. Here we report a molecular hybrid at the buried interface in inverted perovskite solar cells that co-assembled the popular self-assembled molecule [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) with the multiple aromatic carboxylic acid 4,4',4″-nitrilotribenzoic acid (NA) to improve the heterojunction interface. The molecular hybrid of Me-4PACz with NA could substantially improve the interfacial characteristics. The resulting inverted perovskite solar cells demonstrated a record certified steady-state efficiency of 26.54%. Crucially, this strategy aligns seamlessly with large-scale manufacturing, achieving one of the highest certified power conversion efficiencies for inverted mini-modules at 22.74% (aperture area 11.1 cm2). Our device also maintained 96.1% of its initial power conversion efficiency after more than 2,400 h of 1-sun operation in ambient air.

Surface Reconstruction for Efficient NiOx-Based Inverted Perovskite Solar Cells

Functional agents are verified to efficiently enhance device performance of perovskite solar cells (PSCs) through surface engineering. However, the influence of intrinsic characteristics of molecules on final device performance is overlooked. Here, a surface reconstruction strategy is developed to enhance the efficiency of inverted PSCs by mitigating the adverse effects of lead chelation (LC) molecules. Bathocuproine (BCP) is chosen as the representative of LC molecules for its easy accessibility and outstanding optoelectronic properties. During this strategy, BCP molecules on perovskite surface are first dissolved in solvents and then captured specially by undercoordinated Pb2+ ions, preventing adverse n-type doping by the molecules themselves. In this case, the BCP molecule exhibits outstanding passivation effect on perovskite surface, which leads to an obviously increased open-circuit voltage (VOC). Therefore, a record power conversion efficiency of 25.64% for NiOx-based inverted PSCs is achieved, maintaining over 80% of initial efficiency after exposure to ambient condition for ≈1500 h.

In Situ Buried Interface Engineering towards Printable Pb-Sn Perovskite Solar Cells

High-efficiency Pb-Sn narrow-bandgap perovskite solar cells (PSCs) heavily rely on PEDOT:PSS as the hole-transport layer (HTL) owing to its excellent electrical conductivity, dopant-free nature, and facile solution processability. However, the shallow work function (WF) of PEDOT:PSS consequently results in severe minority carrier recombination at the perovskite/HTL interface. Here, we tackle this issue by an in situ interface engineering strategy using a new molecule called 2-fluoro benzylammonium iodide (FBI) that suppresses nonradiative recombination near the Pb-Sn perovskite (FA0.6MA0.4Pb0.4Sn0.6I3)/HTL bottom interface. The WF of PEDOT:PSS increases by 0.1 eV with FBI modification, resulting in Pb-Sn PSCs with 20.5% efficiency and an impressive VOC of 0.843 V. Finally, we have successfully transferred our in situ buried interface modification strategy to fabricate blade-coated FA0.6MA0.4Pb0.4Sn0.6I3 PSCs with 18.3% efficiency and an exceptionally high VOC of 0.845 V.

High-Efficiency Perovskite Solar Cells with Improved Interfacial Charge Extraction by Bridging Molecules

The interface between the perovskite layer and electron transporting layer is a critical determinate for the performance and stability of perovskite solar cells (PSCs). The heterogeneity of the interface critically affects the carrier dynamics at the buried interface. To address this, a bridging molecule, (2-aminoethyl)phosphonic acid (AEP), is introduced for the modification of SnO2/perovskite buried interface in n-i-p structure PSCs. The phosphonic acid group strongly bonds to the SnO2 surface, effectively suppressing the surface carrier traps and leakage current, and uniforming the surface potential. Meanwhile, the amino group influences the growth of perovskite film, resulting in higher crystallinity, phase purity, and fewer defects. Furthermore, the bridging molecules facilitate the charge extraction at the interface, as indicated by the femtosecond transient reflection (fs-TR) spectroscopy, leading to champion power conversion efficiency (PCE) of 26.40% (certified 25.98%) for PSCs. Additionally, the strengthened interface enables improved operational durability of ≈1400 h for the unencapsulated PSCs under ISOS-L-1I protocol.

Indium Tin Oxide Induced Internal Positive Feedback and Indium Ion Transport in Perovskite Solar Cells

Stability is the most pressing challenge hindering the commercialization of perovskite solar cells (PSCs), and previous efforts focused more on enhancing the resistance of PSCs to external stimulus. Here, we found that the indium tin oxide (ITO) will deteriorate the photovoltaic performance of PSCs through positive feedback cycles. Specifically, the perovskite degradation products will cross the electron transport layer to chemically etch the electrode ITO to generate In3+, which will migrate upwards into the perovskite film. Then, the reaction that corrodes ITO consumes the decomposition products of perovskite and shifts the balance of the perovskite decomposition reaction, further promoting the degradation and thus falling into a positive feedback cycle. Moreover, the In3+ in the perovskite film was found to accumulate at the upper surface, which would lead to n-type doping of perovskite film to form the energy barrier for interface carrier extraction. Subsequently, the chelating molecule ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) was introduced onto ITO to firmly chelate the In3+ and prevent it from migrating upward, thus breaking this internal positive feedback cycle and significantly enhancing the efficiency and stability of PSCs. This work provides new perspectives for understanding the mechanism of photovoltaic performance loss and ionic transport in PSCs.

Bottom-Up Defect Modification Through Oily-Allicin Modified Buried Interface Achieving Highly Efficient and Stable Perovskite Solar Cells

The buried interface properties of the perovskite solar cells (PSCs) play a crucial role in the power conversion efficiency (PCE) and operational stability. The metal-oxide/perovskite heterogeneous interfaces are highly defective and cause serious ion migration. However, the buried and unexposed bottom interface and simultaneous stabilization of grain boundaries receive less attention and effective solutions. To tackle this problem, a solid-liquid strategy is employed by introducing oily-additive allicin at the buried interface to passivate the shallow (VI and Vo) and deep traps (VPb and PbI). Interestingly, oily status allicin fills the pinholes at the heterointerface and wraps the perovskite grains, suppressing the ion migration during the photoaging process. As a result, an outstanding PCE of 25.07% is achieved with a remarkable fill factor (FF) of 84.03%. The modified devices can maintain 94.51% of the original PCE after light soaking under 1-sun illumination for 1000 h. This work demonstrates a buried interface modification method that employs an eco-friendly additive, which helps promote the development of PSCs with high performance and stability.

A crystal capping layer for formation of black-phase FAPbI3 perovskite in humid air

Black-phase formamidinium lead iodide (α-FAPbI3) perovskites are the desired phase for photovoltaic applications, but water can trigger formation of photoinactive impurity phases such as δ-FAPbI3. We show that the classic solvent system for perovskite fabrication exacerbates this reproducibility challenge. The conventional coordinative solvent dimethyl sulfoxide (DMSO) promoted δ-FAPbI3 formation under high relative humidity (RH) conditions because of its hygroscopic nature. We introduced chlorine-containing organic molecules to form a capping layer that blocked moisture penetration while preserving DMSO-based complexes to regulate crystal growth. We report power conversion efficiencies of >24.5% for perovskite solar cells fabricated across an RH range of 20 to 60%, and 23.4% at 80% RH. The unencapsulated device retained 96% of its initial performance in air (with 40 to 60% RH) after 500-hour maximum power point operation.

Enhancing the Efficiency and Stability of Inverted Formamidinium-Cesium Lead-Triiodide Perovskite Solar Cells through Lewis Base Pretreatment of Buried Interfaces

Mixed components of formamidinium(FA) and cesium (Cs)-based perovskite solar cells are the most hopeful for commercialization owing to their excellent operational and phase stabilities, especially for devices with inverted structure. The nonradiative recombination of carriers can be effectively suppressed through interface optimization, therefore, the performance of devices can be improved. Notably, the buried interface emerges as critical aspects such as charge transport, charge recombination kinetics, and morphology of perovskite films. This study focuses on a straightforward yet effective approach to overcome buried interface challenges between organic polymers (poly(-triarylamine) (PTAA) and FACs-based perovskite films. The PTAA substrate is pretreated with a Lewis base known as 2-butynoic acid (BA) with a C═O functional group. First, it can be an interfacial buffering layer, harmonizing stress mismatch between the perovskite and PTAA layers, consequently optimizing crystallization and improving perovskite film quality. Second, Pb2+ defect can be passivated at the buried interface of the perovskite film through binding with the C═O group of the BA molecule. This dual-function strategy leads to a substantial enhancement in both photoelectric conversion efficiency (PCE) and stability of devices. Finally, the PCE of the device-modified buried interface with BA reaches an impressive 23.33%. Furthermore, unencapsulated devices with BA treatment maintain approximately 94% of their initial efficiency after aging at maximum power point tracking for 1000 h.

Fusing Science with Industry: Perovskite Photovoltaics Moving Rapidly into Industrialization

The organic-inorganic lead halide per materials have emerged as highly promising contenders in the field of photovoltaic technology, offering exceptional efficiency and cost-effectiveness. The commercialization of perovskite photovoltaics hinges on successfully transitioning from lab-scale perovskite solar cells to large-scale perovskite solar modules (PSMs). However, the efficiency of PSMs significantly diminishes with increasing device area, impeding commercial viability. Central to achieving high-efficiency PSMs is fabricating uniform functional films and optimizing interfaces to minimize energy loss. This review sheds light on the path toward large-scale PSMs, emphasizing the pivotal role of integrating cutting-edge scientific research with industrial technology. By exploring scalable deposition techniques and optimization strategies, the advancements and challenges in fabricating large-area perovskite films are revealed. Subsequently, the architecture and contact materials of PSMs are delved while addressing pertinent interface issues. Crucially, efficiency loss during scale-up and stability risks encountered by PSMs is analyzed. Furthermore, the advancements in industrial efforts toward perovskite commercialization are highlighted, emphasizing the perspective of PSMs in revolutionizing renewable energy. By highlighting the scientific and technical challenges in developing PSMs, the importance of combining science and industry to drive their industrialization and pave the way for future advancements is stressed.

Defect Passivation and Crystallization Regulation for Efficient and Stable Formamidinium Lead Iodide Solar Cells with Multifunctional Amidino Additive

Amidino-based additives show great potential in high-performance perovskite solar cells (PSCs). However, the role of different functional groups in amidino-based additives have not been well elucidated. Herein, two multifunctional amidino additives 4-amidinobenzoic acid hydrochloride (ABAc) and 4-amidinobenzamide hydrochloride (ABAm) are employed to improve the film quality of formamidinium lead iodide (FAPbI3) perovskites. Compared with ABAc, the amide group imparts ABAm with larger dipole moment and thus stronger interactions with the perovskite components, i.e., the hydrogen bonds between N…H and I- anion and coordination bonds between C = O and Pb2+ cation. It strengthens the passivation effect of iodine vacancy defect and slows down the crystallization process of α-FAPbI3, resulting in the significantly reduced non-radiative recombination, long carrier lifetime of 1.7 µs, uniformly large crystalline grains, and enhances hydrophobicity. Profiting from the improved film quality, the ABAm-treated PSC achieves a high efficiency of 24.60%, and maintains 93% of the initial efficiency after storage in ambient environment for 1200 hours. This work provides new insights for rational design of multifunctional additives regarding of defect passivation and crystallization control toward highly efficient and stable PSCs.

Precursor-Engineered Volatile Inks Enable Reliable Blade-Coating of Cesium-Formamidinium Perovskites Toward Fully Printed Solar Modules

Reliable fabrication of large-area perovskite films with antisolvent-free printing techniques requires high-volatility solvents, such as 2-methoxyethanol (2ME), to formulate precursor inks. However, the fabrication of high-quality cesium-formamidinium (Cs-FA) perovskites has been hampered using volatile solvents due to their poor coordination with the perovskite precursors. Here, this issue is resolved by re-formulating a 2ME-based Cs0.05FA0.95PbI3 ink using pre-synthesized single crystals as the precursor instead of the conventional mixture of raw powders. The key to obtaining high-quality Cs-FA films lies in the removal of colloidal particles from the ink and hence the suppression of colloid-induced heterogeneous nucleation, which kinetically facilitates the growth of as-formed crystals toward larger grains and improved film crystallinity. Employing the precursor-engineered volatile ink in the vacuum-free, fully printing processing of solar cells (with carbon electrode), a power conversion efficiency (PCE) of 19.3%, a T80 (80% of initial PCE) of 1000 h in ISOS-L-2I (85 °C/1 Sun) aging test and a substantially reduced bill of materials are obtained. The reliable coating methodology ultimately enables the fabrication of carbon-electrode mini solar modules with a stabilized PCE of 16.2% (average 15.6%) representing the record value among the fully printed counterparts and a key milestone toward meeting the objectives for a scalable photovoltaic technology.

Defect Engineering at Buried Interface of Perovskite Solar Cells

Perovskite solar cells (PSC) have developed rapidly since the past decade with the aim to produce highly efficient photovoltaic technology at a low cost. Recently, physical and chemical defects at the buried interface of PSC including vacancies, impurities, lattice strain, and voids are identified as the next formidable hurdle to the further advancement of the performance of devices. The presence of these defects has unfavorably impacted many optoelectronic properties in the PSC, such as band alignment, charge extraction/recombination dynamics, ion migration behavior, and hydrophobicity. Herein, a broad but critical discussion on various essential aspects related to defects at the buried interface is provided. In particular, the defects existing at the surface of the underlying charge transporting layer (CTL) and the bottom surface of the perovskite film are initially elaborated. In situ and ex situ characterization approaches adopted to unveil hidden defects are elucidated to determine their influence on the efficiency, operational stability, and photocurrent-voltage hysteresis of PSC. A myriad of innovative strategies including defect management in CTL, the introduction of passivation materials, strain engineering, and morphological control used to address defects are also systematically elucidated to catalyze the further development of more efficient, reliable, and commercially viable photovoltaic devices.

Controlled NiOx Defect Engineering to Harnessing Redox Reactions in Perovskite Photovoltaic Cells via Atomic Layer Deposition

Albeit the undesirable attributes of NiOx, such as low conductivity, unmanageable defects, and redox reactions occurring at the perovskite/NiOx interface, which impede the progress in inverted perovskite solar cells (i-PSCs), it is the most favorable choice of technology for industrialization of PSCs. In this study, we propose a novel Ni vacancy defect modulate approach to leverage the conformal growth and surface self-limiting reaction characteristics of the atomic layer deposition (ALD)-fabricated NiOx by varying the O2 plasma injection time (tOE) to induce self-doping. Consequently, NiOx thin films with enhanced conductivity, an appropriate Ni3+/Ni2+ ratio, stable surface states, and ultrathinness are realized as hole-transporting layers (HTLs) in p-i-n PSCs. As a result of these improvements, ALD-NiOx-based devices exhibit the highest power conversion efficiency (PCE) of 19.86% and a fill factor (FF) of 81.86%. Notably, the optimal interfacial defects effectively suppressed the severe reaction between the perovskite and NiOx. This suppression is evidenced by the lowest decay rate observed in a harsh environment, lasting for 500 consecutive hours. The proposed approach introduces the possibility of a hierarchical distribution of defects and offers feasibility for the fabrication of large-area, uniform, and high-quality films.

Eliminating Voids and Residual PbI2 beneath a Perovskite Film via Buried Interface Modification for Efficient Solar Cells

The commercialization process of perovskite solar cells (PSCs) is markedly restricted by the power conversion efficiency (PCE) and long-term stability. During fabrication and operation, the bottom interface of the organic-inorganic hybrid perovskite layer frequently exhibits voids and residual PbI2, while these defects inevitably act as recombination centers and degradation sites, affecting the efficiency and stability of the devices. Therefore, the degradation and nonradiative recombination originating from the buried interface should be thoroughly resolved. Here, we report a multifunctional passivator by introducing malonic dihydrazide as an interfacial chemical bridge between the electron transport layer and the perovskite (PVK) layer. MADH with hydrazine groups improves the surface affinity of SnO2 and provides nucleation sites for the growth of PVK, leading to the reduced residual PbI2 and the voids resulting from the inhomogeneous solvent volatilization at the bottom interface. Meanwhile, the hydrazine group and carbonyl group synergistically coordinate with Pb2+ to improve the crystal growth environment, reducing the number of Pb-related defects. Eventually, the PCE of the PSCs is significantly enhanced benefiting from the reduced interfacial defects and the increased carrier transport. Moreover, the reductive nature of hydrazide further inhibits I2 generation during long-term operation, and the device retains 90% of the initial PCE under a 1 sun continuous illumination exposure of 700 h.

Efficient Blade-Coated p-i-n Perovskite Solar Cells and Modules Enabled by Effective Molecular N Doping

N doping is an essential strategy to prolong electron diffusion length and improve the photovoltaic performance of p-i-n structured perovskite solar devices, but current n-dopants generally suffer from air instability, poor compatibility with perovskites, and the compensation from perovskite intrinsic defects, thus limiting their doping effectiveness. To address these issues, in this work, a new perovskite n-doping strategy is developed by incorporating an air-stable n-dopant (1-ethyl-3-methylimidazolium-2-carboxylate, EMIC) that has no detrimental effects on perovskite crystallinity and morphology. EMIC is soluble in most polar solvents and can be readily introduced into perovskite precursor solutions. Upon thermal annealing of perovskite films, the decarboxylation of EMIC releases imidazolylidene, a reactive species that highly tends to donate electrons and thus efficiently prolongs the electron diffusion length from 0.57 µm to over 1.21 µm. As a result, the blade-coated perovskite solar cells and modules realize high power conversion efficiencies of 24.3% and 20.6% at 7.4 mm2 and 25.0 cm2 aperture areas, respectively.

Flexible Indoor Perovskite Solar Cells by In Situ Bottom-Up Crystallization Modulation and Interfacial Passivation

A robust perovskite-buried interface is pivotal for achieving high-performance flexible indoor photovoltaics as it significantly influences charge transport and extraction efficiency. Herein, a molecular bridge strategy is introduced utilizing sodium 2-cyanoacetate (SZC) additive at the perovskite-buried interface to simultaneously achieve in situ passivation of interfacial defects and bottom-up crystallization modulation, resulting in high-performance flexible indoor photovoltaic applications. Supported by both theoretical calculations and experimental evidences, it illustrates how SZCs serve as molecular bridges, establishing robust bonds between SnO2 transport layer and perovskite, mitigating oxygen vacancy defects and under-coordinated Pb defects at interface during flexible fabrication. This, in turn, enhances interfacial energy level alignment and facilitates efficient carrier transport. Moreover, this in situ investigation of perovskite crystallization dynamics reveals bottom-up crystallization modulation, extending perovskite growth at the buried interface and influencing subsequent surface recrystallization. This results in larger crystalline grains and improved lattice strain of the perovskite during flexible fabrication. Finally, the optimized flexible solar cells achieve an impressive efficiency exceeding 41% at 1000 lux, with a fill factor as high as 84.32%. The concept of the molecular bridge represents a significant advancement in enhancing the performance of perovskite-based flexible indoor photovoltaics for the upcoming era of Internet of Things (IoT).

Suppressing Ion Migration by Synergistic Engineering of Anion and Cation toward High-Performance Inverted Perovskite Solar Cells and Modules

Ion migration-induced intrinsic instability and large-area fabrication pose a tough challenge for the commercial deployment of perovskite photovoltaics. Herein, an interface heterojunction and metal electrode stabilization strategy is developed by suppressing ion migration via managing lead-based imperfections. After screening a series of cations and nonhalide anions, the ideal organic salt molecule dimethylammonium trifluoroacetate (DMATFA) consisting of dimethylammonium (DMA+) cation and trifluoroacetate (TFA-) anion is selected to manipulate the surface of perovskite films. DMA+ enables the conversion of active excess and/or unreacted PbI2 into stable new phase DMAPbI3, inhibiting photodecomposition of PbI2 and ion migration. Meanwhile, TFA- can suppress iodide ion migration through passivating undercoordinated Pb2+ and/or iodide vacancies. DMA+ and TFA- synergistically stabilize the heterojunction interface and silver electrode. The DMATFA-treated inverted perovskite solar cells and modules achieve a maximum efficiency of 25.03% (certified 24.65%, 0.1 cm2) and 20.58% (63.74 cm2), respectively, which is the record efficiency ever reported for the devices based on vacuum flash evaporation technology. The DMATFA modification results in outstanding operational stability, as evidenced by maintaining 91% of its original efficiency after 1520 h of maximum power point continuous tracking.

Realizing Stable Perovskite Solar Cells with Efficiency Exceeding 25.6% Through Crystallization Kinetics and Spatial Orientation Regulation

Organic-inorganic hybrid perovskites have emerged as highly promising candidates for photovoltaic applications, owing to the exceptional optoelectronic properties and low cost. Nonetheless, the performance and stability of solar cells suffer from the defect states of perovskite films aroused by non-optically active phases and non-centralized crystal orientation. Herein, a versatile organic molecule, Hydantoin, to modulate the crystallization of perovskite, is developed. Benefiting from the diverse functional groups, more spatially oriented perovskite films with high crystallinity are formed. This enhancement is accompanied by a conspicuous reduction in defect density, yielding efficiency of 25.66% (certified 25.15%), with superb environmental stability. Notably, under the standard measurement conditions (ISOS-L-1I), the maximum power point (MPP) output maintains 96.8% of the initial efficiency for 1600 h and exhibits excellent ion migration suppression. The synergistic regulation of crystallization and spatial orientation offers novel avenues for propelling perovskite solar cell (PSC) development.

Unlocking interfaces in photovoltaics

Eliminating defects at interfaces enables perovskites to approach efficiency limits.

Modulating secondary growth of perovskite grains through residual solvent evaporation

Over the past decade, perovskite solar cells (PSCs) have attracted enormous attention due to their high performance. One key to fabricating high-quality perovskite films lies in controlling the volatilization rate of residual solvents during the annealing process. This study systematically investigates how different protective substrates affect the volatilization rate of residual solvent in perovskite films. By adjusting the direction and rate of evaporation, the supersaturation time of the solution was precisely controlled, leading to effective recrystallization of the grains. Concurrently, the annealing time was optimized to enhance film quality further. This optimization aimed to increase crystallinity, reduce defects, and thereby minimize non-radiative recombination centers. Implementing these methodologies, particularly the use of filter paper as a protective substrate during a 2-minute annealing process, significantly improved the fill factor (FF) and open-circuit voltage (VOC) of the PSCs. This led to a remarkable 5.26% improvement in power conversion efficiency (PCE) compared to control devices. The strategies employed in this work demonstrate significant potential in improving PSC film quality. This approach not only advances our understanding of film formation dynamics but also provides a practical guideline for future PSC fabrication.

Highly Efficient and Scalable p-i-n Perovskite Solar Cells Enabled by Poly-metallocene Interfaces

Inverted p-i-n perovskite solar cells (PSCs) are easy to process but need improved interface characteristics with reduced energy loss to prevent efficiency drops when increasing the active photovoltaic area. Here, we report a series of poly ferrocenyl molecules that can modulate the perovskite surface enabling the construction of small- and large-area PSCs. We found that the perovskite-ferrocenyl interaction forms a hybrid complex with enhanced surface coordination strength and activated electronic states, leading to lower interfacial nonradiative recombination and charge transport resistance losses. The resulting PSCs achieve an enhanced efficiency of up to 26.08% for small-area devices and 24.51% for large-area devices (1.0208 cm2). Moreover, the large-area PSCs maintain >92% of the initial efficiency after 2000 h of continuous operation at the maximum power point under 1-sun illumination and 65 °C.

Equally Efficient Perovskite Solar Cells and Modules Fabricated via N-Ethyl-2-Pyrrolidone Optimized Vacuum-Flash

Efficiency reduction in perovskite solar cells (PSCs) during the magnification procedure significantly hampers commercialization. Vacuum-flash (VF) has emerged as a promising method to fabricate PSCs with consistent efficiency across scales. However, the slower solvent removal rate of VF compared to the anti-solvent method leads to perovskite films with buried defects. Thus, this work employs low-toxic Lewis base ligand solvent N-ethyl-2-pyrrolidone (NEP) to improve the nucleation process of perovskite films. NEP, with a mechanism similar to that of N-methyl-2-pyrrolidone in FA-based perovskite formation, enhances the solvent removal speed owing to its lower coordination ability. Based on this strategy, p-i-n PSCs with an optimized interface attain a power conversion efficiency (PCE) of 24.19% on an area of 0.08 cm2. The same nucleation process enables perovskite solar modules (PSMs) to achieve a certified PCE of 23.28% on an aperture area of 22.96 cm2, with a high geometric fill factor of 97%, ensuring nearly identical active area PCE (24%) in PSMs as in PSCs. This strategy highlights the potential of NEP as a ligand solvent choice for the commercialization of PSCs.

Efficient and Stable Inverted Perovskite Solar Modules Enabled by Solid-Liquid Two-Step Film Formation

A considerable efficiency gap exists between large-area perovskite solar modules and small-area perovskite solar cells. The control of forming uniform and large-area film and perovskite crystallization is still the main obstacle restricting the efficiency of PSMs. In this work, we adopted a solid-liquid two-step film formation technique, which involved the evaporation of a lead iodide film and blade coating of an organic ammonium halide solution to prepare perovskite films. This method possesses the advantages of integrating vapor deposition and solution methods, which could apply to substrates with different roughness and avoid using toxic solvents to achieve a more uniform, large-area perovskite film. Furthermore, modification of the NiOx/perovskite buried interface and introduction of Urea additives were utilized to reduce interface recombination and regulate perovskite crystallization. As a result, a large-area perovskite film possessing larger grains, fewer pinholes, and reduced defects could be achieved. The inverted PSM with an active area of 61.56 cm2 (10 × 10 cm2 substrate) achieved a champion power conversion efficiency of 20.56% and significantly improved stability. This method suggests an innovative approach to resolving the uniformity issue associated with large-area film fabrication.

Key Roles of Interfaces in Inverted Metal-Halide Perovskite Solar Cells

Metal-halide perovskite solar cells (PSCs), an emerging technology for transforming solar energy into a clean source of electricity, have reached efficiency levels comparable to those of commercial silicon cells. Compared with other types of PSCs, inverted perovskite solar cells (IPSCs) have shown promise with regard to commercialization due to their facile fabrication and excellent optoelectronic properties. The interlayer interfaces play an important role in the performance of perovskite cells, not only affecting charge transfer and transport, but also acting as a barrier against oxygen and moisture permeation. Herein, we describe and summarize the last three years of studies that summarize the advantages of interface engineering-based advances for the commercialization of IPSCs. This review includes a brief introduction of the structure and working principle of IPSCs, and analyzes how interfaces affect the performance of IPSC devices from the perspective of photovoltaic performance and device lifetime. In addition, a comprehensive summary of various interface engineering approaches to solving these problems and challenges in IPSCs, including the use of interlayers, interface modification, defect passivation, and others, is summarized. Moreover, based upon current developments and breakthroughs, fundamental and engineering perspectives on future commercialization pathways are provided for the innovation and design of next-generation IPSCs.

Regulating Charge Transport Dynamics at the Buried Interface and Bulk of Perovskites by Tailored-phase Two-dimensional Crystal Seed Layer

Targeting the trap-assisted non-radiative recombination losses and photochemical degradation occurring at the interface and bulk of perovskite, especially the overlooked buried bottom interface, a strategy of tailored-phase two-dimensional (TP-2D) crystal seed layer has been developed to improve the charge transport dynamics at the buried interface and bulk of perovskite films. Using this approach, TP-2D layer constructed by TP-2D crystal seeds at the buried interface can induce the formation of homogeneous interface electric field, which effectively suppress the accumulation of charge carriers at the buried interface. Additionally, the presence of TP-2D crystal seed has a positive effect on the crystallization process of the upper perovskite film, leading to optimized crystal quality and thus promoted charge transport inside bulk perovskites. Ultimately, the best performing PSCs based on TP-2D layer deliver a power conversion efficiency of 24.58 %. The devices exhibit an improved photostability with 88.4 % of their initial PCEs being retained after aging under continuous 0.8-sun illumination for 2000 h in air. Our findings reveal how to regulate the charge transport dynamics of perovskite bulk and interface by introducing homogeneous components.

Gas-Liquid Interface Route to Hybrid Copper Bromine Perovskite Single-Crystal Membrane with Dielectric Transitions and Ferromagnetic Exchanges

Single-crystal membranes (SCMs) show great promise in the fields of sensors, light-emitting diodes, and photodetection. However, the growth of a large-area single-crystal membranes is challenging. We report a new organic-inorganic SCMs [HCMA]2CuBr4 (HCMA = cyclohexanemethylamine) crystallized at the gas-liquid interface. It also has low-temperature ferromagnetic order, high-temperature dielectric anomalies, and narrow band gap indirect semiconductor properties. Specifically, the reversible phase transition of the compound occurs at 350/341 K on cooling/heating and exhibits dielectric anomalies and stable switching performance near the phase transition temperature. The ferromagnetic exchange interaction in the inorganic octahedra and the organic layer enables ferromagnetic ordering at low-temperature 10 K. Finally, the single crystal exhibits an indirect semiconducting property with a narrow band gap of 0.99 eV. Such rich multichannel physical properties make it a potential application in photodetection, information storage and sensors.

Narrow Bandgap Metal Halide Perovskites for All-Perovskite Tandem Photovoltaics

All-perovskite tandem solar cells are attracting considerable interest in photovoltaics research, owing to their potential to surpass the theoretical efficiency limit of single-junction cells, in a cost-effective sustainable manner. Thanks to the bandgap-bowing effect, mixed tin-lead (Sn-Pb) perovskites possess a close to ideal narrow bandgap for constructing tandem cells, matched with wide-bandgap neat lead-based counterparts. The performance of all-perovskite tandems, however, has yet to reach its efficiency potential. One of the main obstacles that need to be overcome is the─oftentimes─low quality of the mixed Sn-Pb perovskite films, largely caused by the facile oxidation of Sn(II) to Sn(IV), as well as the difficult-to-control film crystallization dynamics. Additional detrimental imperfections are introduced in the perovskite thin film, particularly at its vulnerable surfaces, including the top and bottom interfaces as well as the grain boundaries. Due to these issues, the resultant device performance is distinctly far lower than their theoretically achievable maximum efficiency. Robust modifications and improvements to the surfaces of mixed Sn-Pb perovskite films are therefore critical for the advancement of the field. This Review describes the origins of imperfections in thin films and covers efforts made so far toward reaching a better understanding of mixed Sn-Pb perovskites, in particular with respect to surface modifications that improved the efficiency and stability of the narrow bandgap solar cells. In addition, we also outline the important issues of integrating the narrow bandgap subcells for achieving reliable and efficient all-perovskite double- and multi-junction tandems. Future work should focus on the characterization and visualization of the specific surface defects, as well as tracking their evolution under different external stimuli, guiding in turn the processing for efficient and stable single-junction and tandem solar cell devices.

Current State and Future Perspectives of Printable Organic and Perovskite Solar Cells

Photovoltaic technology presents a sustainable solution to address the escalating global energy consumption and a reliable strategy for achieving net-zero carbon emissions by 2050. Emerging photovoltaic technologies, especially the printable organic and perovskite solar cells, have attracted extensive attention due to their rapidly transcending power conversion efficiencies and facile processability, providing great potential to revolutionize the global photovoltaic market. To accelerate these technologies to translate from the laboratory scale to the industrial level, it is critical to develop well-defined and scalable protocols to deposit high-quality thin films of photoactive and charge-transporting materials. Herein, the current state of printable organic and perovskite solar cells is summarized and the view regarding the challenges and prospects toward their commercialization is shared. Different printing techniques are first introduced to provide a correlation between material properties and printing mechanisms, and the optimization of ink formulation and film-formation during large-area deposition of different functional layers in devices are then discussed. Engineering perspectives are also discussed to analyze the criteria for module design. Finally, perspectives are provided regarding the future development of these solar cells toward practical commercialization. It is believed that this perspective will provide insight into the development of printable solar cells and other electronic devices.

In-Situ Polymer Framework Strategy Enabling Printable and Efficient Perovskite Solar Cells by Mitigating "Coffee Ring" Effect

Organic-inorganic hybrid perovskites are considered ideal candidates for future photovoltaic applications due to their excellent photovoltaic properties. Although solution-printed manufacturing has shown inherent potential for the low-cost, high-throughput production of thin-film semiconductor electronics, the high-quality and high-reproducibility deposition of large-area perovskite remains a bottleneck that restricts their commercialization due to the droplet coffee-ring effect (CRE). In this study, these issues are addressed by introducing an in situ polymer framework. The 3D framework formed by spontaneous cross-linking improves the precursor viscosity and homogenizes its heat diffusion coefficient, counteracting the lateral capillary flow of the colloidal particles and anchoring their flocculent movement. Thus, the Marangoni convection intensity is properly controlled to ensure high-quality perovskite films, which significantly enhances reproducibility in printing efficient photovoltaics by mitigating the CRE. Subsequently, the perovskite solar cells and modules achieve power conversion efficiencies of 23.94 and 17.53%, and exhibit positive environmental stability, retaining over 90 and 78% efficiency after storage for 2500 and 1600 h, respectively. This work may serves as a foundation for exploring precursor rheology to match the homogeneous deposition requirements of perovskite photovoltaics and facilitating the advancement of their printing manufacturing and commercialization transition.

Double-side 2D/3D heterojunctions for inverted perovskite solar cells

Defects at the top and bottom interfaces of three-dimensional (3D) perovskite photoabsorbers diminish the performance and operational stability of perovskite solar cells owing to charge recombination, ion migration and electric-field inhomogeneities1-5. Here we demonstrate that long alkyl amine ligands can generate near-phase-pure 2D perovskites at the top and bottom 3D perovskite interfaces and effectively resolve these issues. At the rear-contact side, we find that the alkyl amine ligand strengthens the interactions with the substrate through acid-base reactions with the phosphonic acid group from the organic hole-transporting self-assembled monolayer molecule, thus regulating the 2D perovskite formation. With this, inverted perovskite solar cells with double-side 2D/3D heterojunctions achieved a power conversion efficiency of 25.6% (certified 25.0%), retaining 95% of their initial power conversion efficiency after 1,000 h of 1-sun illumination at 85 °C in air.

Strain regulates the photovoltaic performance of thick-film perovskites

Perovskite photovoltaics, typically based on a solution-processed perovskite layer with a film thickness of a few hundred nanometres, have emerged as a leading thin-film photovoltaic technology. Nevertheless, many critical issues pose challenges to its commercialization progress, including industrial compatibility, stability, scalability and reliability. A thicker perovskite film on a scale of micrometres could mitigate these issues. However, the efficiencies of thick-film perovskite cells lag behind those with nanometre film thickness. With the mechanism remaining elusive, the community has long been under the impression that the limiting factor lies in the short carrier lifetime as a result of defects. Here, by constructing a perovskite system with extraordinarily long carrier lifetime, we rule out the restrictions of carrier lifetime on the device performance. Through this, we unveil the critical role of the ignored lattice strain in thick films. Our results provide insights into the factors limiting the performance of thick-film perovskite devices.

Manipulation of Crystal Orientation and Phase Distribution of Quasi-2D Perovskite through Synergistic Effect of Additive Doping and Spacer Engineering

The diammonium precursor 1,4-phenylenedimethanammonium (PDMA) was used as a large organic spacer for the preparation of Dion-Jacobson-type quasi-2D perovskites (PDMA)(MA)n-1PbnI3n+1 (MA = methylammonium). Films with composition ⟨n⟩ = 5 comprised randomly orientated grains and multiple microstructural domains with locally differing n values. However, by mixing the Dion-Jacobson-type spacer PDMA and the Ruddlesden-Popper-type spacer propylammonium (PA), the crystal orientation in both the vertical and the horizonal directions became regulated. High crystallinity owing to well-matched interlayer distances was observed. Combining this spacer-engineering approach with the addition of methylammonium chloride (MACl) led to full vertical alignment of the crystal orientation. Moreover, the microstructural domains at the substrate interface changed from low-n (n = 1, 2, 3) to high-n (n = 4, 5), which may be beneficial for hole extraction at the interface between perovskite and hole transport layer due to a more finely tuned band alignment. Our work sheds light on manipulating the crystallization behavior of quasi-2D perovskite and further paves the way for highly stable and efficient perovskite devices.

Chiral-Achiral Cations Intercalation Induced Lead-Free Chiral-Polar Hybrid Perovskites Enable Self-Powered X-Ray and Ultraviolet-Visible-Near-Infrared Photo Detection

Lead halide hybrid perovskites have made great progress in direct X-ray detection and broadband photodetection, but the existence of toxic Pb and the demand for external operating voltage have severely limited their further applications and operational stability improvements. Therefore, exploring "green" lead-free hybrid perovskite that can both achieve X-ray detection and broadband photodetection without external voltage is of great importance, but remains severely challenging. Herein, using centrosymmetric (BZA)3BiI6 (1, BZA = benzylamine) as a template, a pair of chiral-polar lead-free perovskites, (BZA)2(R/S-PPA)BiI6 (2-R/S, R/S-PPA = (R/S)-1-Phenylpropylamine) are successfully obtained by introducing chiral aryl cations of (R/S)-1-Phenylpropylamine. Compared to 1, chiral-polar 2-R presents a significant irradiation-responsive bulk photovoltaic effect (BPVE) with an open circuit photovoltage of 0.4 V, which enables it with self-powered X-ray, UV-vis-NIR broadband photodetection. Specifically, 2-R device exhibits an ultralow detection limit of 18.5 nGy s-1 and excellent operational stability. Furthermore, 2-R as the first lead-free perovskite achieves significant broad-spectrum (377-940 nm) photodetection via light-induced pyroelectric effect. This work sheds light on the rational crystal reconstruction engineering and design of "green" hybrid perovskite toward high-demanded self-powered radiation detection and broadband photodetection.

Retarding Ion Migration for Stable Blade-Coated Inverted Perovskite Solar Cells

The fabrication of perovskite solar cells (PSCs) through blade coating is seen as one of the most viable paths toward commercialization. However, relative to the less scalable spin coating method, the blade coating process often results in more defective perovskite films with lower grain uniformity. Ion migration, facilitated by those elevated defect levels, is one of the main triggers of phase segregation and device instability. Here, a bifunctional molecule, p-aminobenzoic acid (PABA), which enhances the barrier to ion migration, induces grain growth along the (100) facet, and promotes the formation of homogeneous perovskite films with fewer defects, is reported. As a result, PSCs with PABA achieved impressive power conversion efficiencies (PCEs) of 23.32% and 22.23% for devices with active areas of 0.1 cm2 and 1 cm2 , respectively. Furthermore, these devices maintain 93.8% of their initial efficiencies after 1 000 h under 1-sun illumination, 75 °C, and 10% relative humidity conditions.

Moisture-Resilient Perovskite Solar Cells for Enhanced Stability

With the rapid rise in device performance of perovskite solar cells (PSCs), overcoming instabilities under outdoor operating conditions has become the most crucial obstacle toward their commercialization. Among stressors such as light, heat, voltage bias, and moisture, the latter is arguably the most critical, as it can decompose metal-halide perovskite (MHP) photoactive absorbers instantly through its hygroscopic components (organic cations and metal halides). In addition, most charge transport layers (CTLs) commonly employed in PSCs also degrade in the presence of water. Furthermore, photovoltaic module fabrication encompasses several steps, such as laser processing, subcell interconnection, and encapsulation, during which the device layers are exposed to the ambient atmosphere. Therefore, as a first step toward long-term stable perovskite photovoltaics, it is vital to engineer device materials toward maximizing moisture resilience, which can be accomplished by passivating the bulk of the MHP film, introducing passivation interlayers at the top contact, exploiting hydrophobic CTLs, and encapsulating finished devices with hydrophobic barrier layers, without jeopardizing device performance. Here, existing strategies for enhancing the performance stability of PSCs are reviewed and pathways toward moisture-resilient commercial perovskite devices are formulated.

Enhancing the Stability and Efficiency of Inverted Perovskite Solar Cells with a Mixed Ammonium Ligands Passivation Strategy

The perovskite solar cell (PSC), which has achieved efficiencies of more than 26%, is expected to be a promising technology that can alternate silicon-based solar cells. However, the performance of PSCs is still limited due to defects and ion migration that occur at the large number of grain boundaries present in perovskite thin films. In this study, the mixed ammonium ligands passivation strategy (MAPS) is demonstrated, which combines n-octylammonium iodide (OAI) and 1,3-diaminopropane (DAP) can effectively suppress the grain boundary defects and ion migration through grain boundaries by the synergistic effect of OAI and DAP, resulting in improved efficiency and stability of PSCs. It has also been revealed that MAPS not only enhances crystallinity and reduces grain boundaries but also improves charge transport while suppressing charge recombination. The MAPS-based opaque PSC shows the best power conversion efficiency (PCE) of 21.29% with improved open-circuit voltage (VOC ) and fill factor (FF), and retained 84% of its initial PCE after 1900 h at 65 °C in N2 atmosphere. Amazingly, the MAPS-based semi-transparent PSC (STP-PSC) retained 94% of their maximum power (21.00% at around 10% AVT) after 1000 h under 1 sun illumination and MAPS-based perovskite submodule (PSM) achieved a PCE of 19.59%, which is among the highest values reported recently.

Crystallization Control Based on the Regulation of Solvent-Perovskite Coordination for High-Performance Ambient Printable FAPbI3 Perovskite Solar Cells

The critical requirement for ambient-printed formamidinium lead iodide (FAPbI3 ) lies in the control of nucleation-growth kinetics and defect formation behavior, which are extensively influenced by interactions between the solvent and perovskite. Here, a strategy is developed that combines a cosolvent and an additive to efficiently tailor the coordination between the solvent and perovskite. Through in situ characterizations, the direct crystallization from the sol-gel phase to α-FAPbI3 is illustrated. When the solvent exhibits strong interactions with the perovskite, the sol-gel phases cannot effectively transform into α-FAPbI3 , resulting in a lower nucleation rate and confined crystal growth directions. Consequently, it becomes challenging to fabricate high-quality void-free perovskite films. Conversely, weaker solvent-perovskite coordination promotes direct crystallization from sol-gel phases to α-FAPbI3 . This process exhibits more balanced nucleation-growth kinetics and restrains the formation of defects and microstrains in situ. This strategy leads to improved structural and optoelectronic properties within the FAPbI3 films, characterized by more compact grain stacking, smoother surface morphology, released lattice strain, and fewer defects. The ambient-printed FAPbI3 perovskite solar cells fabricated using this strategy exhibit a remarkable power conversion efficiency of 24%, with significantly reduced efficiency deviation and negligible decreases in the stabilized output.