A systematic discrepancy between the short circuit current and the integrated quantum efficiency in perovskite solar cells

Controlling the Growth of Cs2PbX4 Nanostructures Enhances the Stability of Inorganic Cesium-Based Perovskite Solar Cells for Potential Low Earth Orbit Applications

Incorporating low-dimensional (LD) materials in perovskite solar cells (PSCs) for interfacial engineering is an effective approach to enhance device performance. However, the growth mechanisms for inorganic LD perovskite nanostructures in cesium-based systems via solution processing are underexplored. This work demonstrates the importance of controlling solvent evaporation dynamics during solution processing to modulate Cs2PbX4 nanomorphology. An evolution of growing Cs2PbX4 nanostructures is demonstrated on CsPbI2Br thin films. Cs2PbX4 nanostructures at CsPbI2Br grain boundaries introduce a passivation effect, improving interfacial quality with the hole transport layer (HTL). Systematic characterization reveals that careful engineering of LD nanostructures strongly impacts the optoelectronic properties of PSCs. Optimized CsPbI2Br/Cs2PbX4 heterostructures enhance the power conversion efficiency (PCE) from an average of 10.8% to 13.5%, achieving a 25% improvement over devices without interfacial engineering. Under a 100 h photovoltaic aging test, the PCE of the control device degraded by 30.7%, whereas the CsCl-treated devices retained 98% of their PCE from the start of the measurement. Post-proton-irradiated PSCs based on Cs2PbX4-modified CsPbI2Br retain up to 96% of their initial PCE of 12.2% after exposure to low Earth orbit-like conditions, maintaining a PCE of 11.7%. In contrast, the control device exhibits significant degradation, with the PCE dropping from 11.5% to 3.1%. These findings deepen our understanding of controlling the morphology of inorganic LD nanomaterials via a solution process. The promising stability of PSCs after interfacial engineering highlights their potential for robust performance under harsh conditions.

Progress and Developments in the Fabrication and Characterization of Metal Halide Perovskites for Photovoltaic Applications

Metal halide perovskites have emerged as a groundbreaking material class for photovoltaic applications, owing to their exceptional optoelectronic properties, tunable bandgap, and cost-effective fabrication processes. This review offers a comprehensive analysis of recent advancements in synthesis, structural engineering, and characterization of metal halide perovskites for efficient solar energy conversion. We explore a range of fabrication techniques, including solution processing, vapor deposition, and nanostructuring, emphasizing their impact on material stability, efficiency, and scalability. Additionally, we discuss key characterization methods, such as X-ray diffraction, electron microscopy, impedance spectroscopy, and optical analysis, that provide insights into the structural, electrical, and optical properties of these materials. Despite significant progress, challenges related to long-term stability, degradation mechanisms, and environmental sustainability persist. This review delves into current strategies for enhancing the durability and performance of perovskite-based photovoltaics and highlights emerging trends in device integration and commercialization. Finally, we provide future perspectives on optimizing material design and overcoming existing limitations to guide continued research in this rapidly advancing field.

Modulating Perovskite Surface Energetics Through Tuneable Ferrocene Interlayers for High-Performance Perovskite Solar Cells

Achieving rational control over chemical and energetic properties at the perovskite/electron transport layer (ETL) interface is crucial for realizing highly efficient and stable next-generation inverted perovskite solar cells (PSCs). To address this, we developed multifunctional ferrocene (Fc)-based interlayers engineered to exhibit adjustable passivating and electrochemical characteristics. These interlayers are designed to reduce non-radiative recombination, and to modulate the work function (WF) and uniformity of the perovskite surface, thereby enhancing device performance. The key role played by the highest occupied molecular orbital energies (EHOMO) of the Fc compounds relative to the perovskite valance band maximum (EVBM) is revealed. This relationship is pivotal in controlling band bending and optimizing charge extraction. Notably, the conformationally flexible and more easily oxidized ferrocenyl-bis-furyl-2-carboxylate (2) is found to more effectively bind with undercoordinated Pb2+ surface sites and modulate interfacial energetics, resulting in inverted PSCs achieving champion efficiencies of 25.16 %. These cells also displayed excellent stability, retaining >92 % of the initial efficiency after 1,000 h of maximum power point operation at 65 °C. By correlating the broadly tunable Fc-EHOMO with a decreased and homogenized perovskite surface WF, our work advances our understanding of Fc-based interlayers and opens new pathways for their application in high-efficiency solar technologies.

Unravelling the Role of Indium in Enhancing the Stability of Mixed Tin-Lead Perovskite Solar Cells

Tin-lead metal halide perovskites show promise as light-absorbing materials with a tunable band gap (1.2-1.4 eV) for efficient perovskite solar cells (PSCs) with less toxicity. However, the instability of the tin(II) ionic state limits the lifetime of their PSCs, which reduces their real-world feasibility. Herein, indium(III) iodide (InI3) is used to modulate the Sn-Pb perovskite crystal lattice to improve the stability of the film, in addition to improving the photovoltaic performance of the corresponding PSC devices. It is found that the indium cation shows an ability to substitute tin(II) vacancies in the perovskite crystal structure, resulting in a more stable structure. The InI3-modified films exhibit enhanced surface morphology and crystallinity, reduced trap state density, and nonradiative recombination in the solar cells expressed in improved device performance of the Sn-Pb-based PSCs from 17.2 to 18.1% and an enhancement in the stability of the perovskite during exposure to elevated temperature and humid atmospheric air.

Incorporating thermal co-evaporation in current-matched all-perovskite triple-junction solar cells

Thermal co-evaporation of halide perovskites is a solution-free, conformal, scalable, and controllable deposition technique with great potential for commercial applications, particularly in multi-junction solar cells. Monolithic triple-junction perovskite solar cells have garnered significant attention because they can achieve very high efficiencies. Nevertheless, challenges arise in fabricating these devices, as they require multiple layers and precise current matching across complex absorber stacks. Here we demonstrate a current-matched monolithic all-perovskite p-i-n triple-junction solar cell enabled by controlled thermal co-evaporation of various absorber layers in the stack. The top and middle subcells were fabricated by developing optimized thermally co-evaporated Cs0.3FA0.7Pb(I0.56Br0.44)3 (1.80 eV bandgap) and FAPbI3 (1.53 eV) perovskites, respectively, while the bottom subcell employed a solution-processed Cs0.25FA0.75Pb0.5Sn0.5I3 (1.25 eV) perovskite. By optimising absorber thicknesses and compositions through optical modelling, we achieve excellent current matching between the top (9.6 mA cm-2), middle (9.3 mA cm-2), and bottom subcells (9.0 mA cm-2), achieving an overall efficiency of 15.8%. Optical modelling simulations suggest that current matching and efficiency up to 11.4 mA cm-2 and 37.6% respectively could be attainable using the latest interlayer materials. This work highlights the potential of scalable vapour-based deposition techniques for advancing multi-junction perovskite-based solar cells, paving the way for future developments in this field.

Regulation of Wide Bandgap Perovskite by Rubidium Thiocyanate for Efficient Silicon/Perovskite Tandem Solar Cells

Developing high-quality wide bandgap (WBG) perovskites with ≈1.7 eV bandgap (Eg) is critical to couple with silicon and create efficient silicon/perovskite tandem devices. The sufferings of large open-circuit voltage (VOC) loss and unstable power output under operation continuously highlight the criticality to fully develop high-quality WBG perovskite films. In this study, rubidium and thiocyanate as additive regulators in WBG perovskites are incorporated, significantly reducing non-radiative recombination, ion-migration, and phase segregation. The optimized 1.66 eV Eg perovskite solar cells achieved state-of-art 1.3 V VOC (0.36 V deficit), and delivered a stabilized power conversion efficiency of 24.3%, along with good device stability (20% degradation (T80) after over 994 h of operation under 1 sun at ≈65°C). When integrated with a flat front side silicon cell, silicon/perovskite two-terminal tandem device (30% efficient) is obtained with a 1.97 V VOC, and T90 operational lifetime of more than 600 h at room temperature.

Solution-Crystalized AgBiS2 Films for Solar Cells Generating a Photo-Current Density Over 31 mA cm-2

In response to the toxic heavy metal absorbers in perovskite solar cells (PSCs), this work focuses on the development of an environmentally friendly simple solution-processed infrared (IR) absorber. In this work, a simple solution-crystallized IR-absorbing AgBiS2 film is reported by spin-coating silver, bismuth nitrates, and thiourea dissolved in dimethylformamide (DMF) to produce thick AgBiS2 film. Extensive optimization of the precursor concentrations thicknesses and conductive substrates used allow for obtaining 250 nm AgBiS2 film with different crystal sizes. When applied as an absorber in solar cells, solution-crystalized AgBiS2 thick film delivers an extraordinarily high current density of over 31 mA cm-2. The devices show high stability under continuous 100 mW cm-2 illumination and when stored in the dark for more than six months. When the AgBiS2 layer is fabricated in a gradient fashion combining one layer of 0.25 m and three layers of 0.5 m precursor concentrations, the efficiency of 5.15% is registered which is the highest reported for the simple solution-crystallized AgBiS2 films.

Approaching Splendid Catalysts for Li-CO2 Battery from the Theory to Practical Designing: A Review

Lithium carbon dioxide (Li-CO2) batteries, noted for their high discharge voltage of approximately 2.8 V and substantial theoretical specific energy of 1876 Wh kg-1, represent a promising avenue for new energy sources and CO2 emission reduction. However, the practical application of these batteries faces significant hurdles, particularly at high current densities and over extended cycle lives, due to their complex reaction mechanisms and slow kinetics. This paper delves into the recent advancements in cathode catalysts for Li-CO2 batteries, with a specific focus on the designing philosophy from composition, geometry, and homogeneity of the catalysts to the proper test conditions and real-world application. It surveys the possible catalytic mechanisms, giving readers a brief introduction of how the energy is stored and released as well as the critical exploration of the relationship between material properties and performances. Specifically, optimization and standardization of test conditions for Li-CO2 battery research is highlighted to enhance data comparability, which is also critical to facilitate the practical application of Li-CO2 batteries. This review aims to bring up inspiration from previous work to advance the design of more effective and sustainable cathode catalysts, tailored to meet the practical demands of Li-CO2 batteries.

In Situ Electrochemical Cobalt Doping in Perovskite-Structured Lanthanum Nickelate Thin Film Toward Energy Conversion Enhancement of Polymer Solar Cells

This study demonstrates that the electrochemical doping of lanthanum nickelate (LNO) with cobalt ions is a promising strategy for enhancing its physical and electrochemical properties, which are critical for energy storage and conversion devices. LNO emerges as a promising hole transport layer (HTL) in solar cells due to its stability, large band gap, and high transparency. Nevertheless, its low conductivity and improperly aligned band positions are persistent problems. Here, in a pioneering endeavor, Co-doped LNO thin films were synthesized electrochemically and applied as the HTL in polymer solar cells (PSCs). Characterization revealed the impact of Co doping on the electrochemical, structural, morphological, and optical properties of LNO thin films. Depending on the Co doping level, PSCs based on 10 mol % Co-doped LNO outperformed pure LNO, achieving a champion efficiency of 6.11% with enhanced short-circuit current density (12.84 mA cm-2), fill factor (68%), open-circuit voltage (0.70 V), and external quantum efficiency (82.6%). This enhancement resulted from decreased series resistance, refined surface morphology, minimized trap-assisted recombination, enhanced conductivity, increased charge carrier production, favorable energy level alignment, and improved current extraction facilitated by LNC0.10O HTL. Moreover, the unencapsulated PSC-LNC0.10O long-term stability notably improved and retained 86% of its initial PCE after 450 h storage in ambient air, 82% after being continuously heated to 85 °C for 300 h, and 80% after operating at maximum power point for 300 h. These findings offer a straightforward approach to enhancing PSC performance through Co doping of LNO, supported by density functional theory (DFT) calculations that validate the experimental results and confirm the improvement in optical properties and stability of PSCs as an HTL.

An Integrated Deposition and Passivation Strategy for Controlled Crystallization of 2D/3D Halide Perovskite Films

This work introduces a simplified deposition procedure for multidimensional (2D/3D) perovskite thin films, integrating a phenethylammonium chloride (PEACl)-treatment into the antisolvent step when forming the 3D perovskite. This simultaneous deposition and passivation strategy reduces the number of synthesis steps while simultaneously stabilizing the halide perovskite film and improving the photovoltaic performance of resulting solar cell devices to 20.8%. Using a combination of multimodal in situ and additional ex situ characterizations, it is demonstrated that the introduction of PEACl during the perovskite film formation slows down the crystal growth process, which leads to a larger average grain size and narrower grain size distribution, thus reducing carrier recombination at grain boundaries and improving the device's performance and stability. The data suggests that during annealing of the wet film, the PEACl diffuses to the surface of the film, forming hydrophobic (quasi-)2D structures that protect the bulk of the perovskite film from humidity-induced degradation.

Passivating Defects via Retarding the Reaction Rate of FAI and PbI2 Enables Stable Perovskite Solar Cells

The two-step sequential deposition strategy has garnered widespread usage in the fabrication of high-performance perovskite solar cells based on FAPbI3. However, the rapid reaction between FAI and PbI2 during preparation often leads to incomplete reactions, reducing the device efficiency and stability. Herein, we introduced a multifunctional additive, 2-thiophenyl trifluoroacetone (TTA), into the FAI precursor. The incorporation of TTA has proven to be highly effective in slowing the reaction rate between FAI and PbI2, resulting in increased perovskite formation and improved efficiency and stability of the devices. TTA's CF3 groups interact with FAI via hydrogen bonding, effectively suppressing FA+ defects. The S and C═O groups share lone pair electrons with uncoordinated Pb2+, leading to a reduction in perovskite film defects and suppressing nonradiative recombination. Additionally, the CF3 groups impart hydrophobicity, protecting the perovskite film from moisture-induced erosion. As a result, the TTA-modified perovskite film achieves a Champion efficiency of 23.42% compared to the control's 21.52, with 20.58% efficiency for a 25 cm2 solar module. Remarkably, the unencapsulated Champion device retains 86% of its initial PCE after 1080 h under dark conditions (60 ± 5 °C, 35 ± 5% RH), indicating enhanced long-term stability. These findings offer a promising and cost-effective tactic for high-quality perovskite film fabrication.

Lamination of >21% Efficient Perovskite Solar Cells with Independent Process Control of Transport Layers and Interfaces

Transport layer and interface optimization is critical for improving the performance and stability of perovskite solar cells (PSCs) but is restricted by the conventional fabrication approach of sequential layer deposition. While the bottom transport layer is processed with minimum constraints, the narrow thermal and chemical stability window of the halide perovskite (HP) layer severely restricts the choice of top transport layer and its processing conditions. To overcome these limitations, we demonstrate lamination of HPs─where two transport layer-perovskite half-stacks are independently processed and diffusion-bonded at the HP-HP interface─as an alternative fabrication strategy that enables self-encapsulated solar cells. Power conversion efficiencies (PCE) of >21% are realized using cells that incorporate a novel transport layer combination along with dual-interface passivation via self-assembled monolayers, both of which are uniquely enabled by the lamination approach. This is the highest reported PCE for any laminated PSC encapsulated between glass substrates. We further show that this approach expands the processing window beyond traditional fabrication processes and is adaptable for different transport layer compositions. The laminated PSCs retained >75% of their initial PCE after 1000 h of 1-sun illumination at 40 °C in air using an all-inorganic transport layer configuration without additional encapsulation. Furthermore, a laminated 1 cm2 device maintained a Voc of 1.16 V. The scalable lamination strategy in this study enables the implementation of new transport layers and interfacial engineering approaches for improving performance and stability.