Efficient and Stable Perovskite Solar Cells by B-Site Compositional Engineered All-Inorganic Perovskites and Interface Passivation

Tailored Colloidal Shapes in Precursor Solutions for Efficient Blade-Coated Perovskite Solar Modules

Metal halide perovskite solar cells (PSCs) have emerged as one of the most promising candidates for next-generation photovoltaic technologies. However, perovskite films deposited by blade-coating usually exhibit inferior film morphology compared to those fabricated by spin-coating, which hinders the power conversion efficiency (PCE) and stability of the scalable perovskite solar modules (PSMs). Herein, ellipsoidal colloids are tailored in the perovskite precursor solution by incorporating perovskite colloids and polymer additives. Compared to unregulated spherical colloids, the ellipsoidal colloids demonstrate more oriented packing during the blade-coating process, which is due to the anisotropic driven force from the fluidic flow in the meniscus. As a result of the improved film morphology, the regulated PSCs and PSMs achieve superior PCE of 24.31% and 21.67% (21.37% certified), respectively, for aperture areas of 0.09 and 13.94 cm2, and 89% initial PCE after 600 h continuous operation.

Powering the Future: Opportunities and Obstacles in Lead-Halide Inorganic Perovskite Solar Cells

Efficiency, stability, and cost are crucial considerations in the development of photovoltaic technology for commercialization. Perovskite solar cells (PSCs) are a promising third-generation photovoltaic technology due to their high efficiency and low-cost potential. However, the stability of organohalide perovskites remains a significant challenge. Inorganic perovskites, based on CsPbX₃ (X = Br-/I-), have garnered attention for their excellent thermal stability and optoelectronic properties comparable to those of organohalide perovskites. Nevertheless, the development of inorganic perovskites faces several hurdles, including the need for high-temperature annealing to achieve the photoactive α-phase and their susceptibility to transitioning into the nonphotoactive δ-phase under environmental stressors, particularly moisture. These challenges impede the creation of high-efficiency, high-stability devices using low-cost, scalable manufacturing processes. This review provides a comprehensive background on the fundamental structural, physical, and optoelectronic properties of inorganic lead-halide perovskites. It discusses the latest advancements in fabricating inorganic PSCs at lower temperatures and under ambient conditions. Furthermore, it highlights the progress in state-of-the-art inorganic devices, particularly those manufactured in ambient environments and at reduced temperatures, alongside simultaneous advancements in the upscaling and stability of inorganic PSCs.

2D Phase Formation on 3D Perovskite: Insights from Molecular Stiffness

Several studies have demonstrated that low-dimensional structures (e.g., two-dimensional (2D)) associated with three-dimensional (3D) perovskite films enhance the efficiency and stability of perovskite solar cells. Here, we aim to track the formation sites of the 2D phase on top of the 3D perovskite and to establish correlations between molecular stiffness and steric hindrance of the organic cations and their influence on the formation and crystallization of 2D/3D. Using cathodoluminescence combined with a scanning electron microscopy technique, we verified that the formation of the 2D phase occurs preferentially on the grain boundaries of the 3D perovskite. This helps explain some passivation mechanisms conferred by the 2D phase on 3D perovskite films. Furthermore, by employing in situ grazing-incidence wide-angle X-ray scattering, we monitored the formation and crystallization of the 2D/3D perovskite using three cations with varying molecular stiffness. In this series of molecules, the formation and crystallization of the 2D phase are found to be dependent on both steric hindrance around the ammonium group and molecular stiffness. Finally, we employed a 2D/3D perovskite heterointerface in a solar cell. The presence of the 2D phase, particularly those formed from flexible cations, resulted in a maximum power conversion efficiency of 21.5%. This study provides insight into critical aspects related to how bulky organic cations' stiffness and steric hindrance influence the formation, crystallization, and distribution of 2D perovskite phases.

Atomic Imaging of Multi-Dimensional Ruddlesden-Popper Interfaces in Lead-Halide Perovskites

Ruddlesden-Popper (RP) interface with defined stacking structure will fundamentally influence the optoelectronic performances of lead-halide perovskite (LHP) materials and devices. However, it remains challenging to observe the atomic local structures in LHPs, especially for multi-dimensional RP interface hidden inside the nanocrystal. In this work, the advantages of two imaging modes in scanning transmission electron microscopy (STEM), including high-angle annular dark field (HAADF) and integrated differential phase contrast (iDPC) STEM, are successfully combined to study the bulk and local structures of inorganic and organic/inorganic hybrid LHP nanocrystals. Then, the multi-dimensional RP interfaces in these LHPs are atomically resolved with clear gap and blurred transition region, respectively. In particular, the complex interface by the RP stacking in 3D directions can be analyzed in 2D projected image. Finally, the phase transition, ion missing, and electronic structures related to this interface are investigated. These results provide real-space evidence for observing and analyzing atomic multi-dimensional RP interfaces, which may help to better understand the structure-property relation of LHPs, especially their complex local structures.

Crystallization Kinetics of Hybrid Perovskite Solar Cells

Metal halide perovskites (MHPs) are considered ideal photovoltaic materials due to their variable crystal material composition and excellent photoelectric properties. However, this variability in composition leads to complex crystallization processes in the manufacturing of Metal halide perovskite (MHP) thin films, resulting in reduced crystallinity and subsequent performance loss in the final device. Thus, understanding and controlling the crystallization dynamics of perovskite materials are essential for improving the stability and performance of PSCs (Perovskite Solar Cells). To investigate the impact of crystallization characteristics on the properties of MHP films and identify corresponding modulation strategies, we primarily discuss the relevant aspects of MHP crystallization kinetics, systematically summarize theoretical methods, and outline modulation techniques for MHP crystallization, including solution engineering, additive engineering, and component engineering, which helps highlight the prospects and current challenges in perovskite crystallization kinetics.

Recent Progress of Low-Toxicity Poor-Lead All-Inorganic Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells (PSCs) have achieved an impressive certified efficiency of 25.7%, which is comparatively higher than that of commercial silicon solar cells (23.3%), showing great potential toward commercialization. However, the low stability and high toxicity due to the presence of volatile organic components and toxic metal lead in the perovskites pose significant challenges. To obtain robust and low-toxicity PSCs, substituting organic cations with pure inorganic cations, and partially or fully replacing the toxic Pb with environmentally benign metals, is one of the promising methods. To date, continuous efforts have been made toward the construction of highly performed low-toxicity inorganic PSCs with astonishing breakthroughs. This review article provides an overview of recent progress in inorganic PSCs in terms of lead-reduced and lead-free compositions. The physical properties of poor-lead all-inorganic perovskites are discussed to unveil the major challenges in this field. Then, it reports notable achievements for the experimental studies to date to figure out feasible methods for efficient and stable poor-lead all-inorganic PSCs. Finally, a discussion of the challenges and prospects for poor-lead all-inorganic PSCs in the future is presented.

Improved Comprehensive Photovoltaic Performance and Mechanisms by Additive Engineering of Ti3C2Tx MXene into CsPbI2Br

CsPbI₂Br is promising in the application of perovskite solar cells (PSCs) owing to its reasonable bandgap and good thermal stability. However, the reported power conversion efficiency (PCE) of the CsPbI₂Br solar cells is still much lower than that of the organic-inorganic hybrid PSCs, mainly due to relatively poor CsPbI₂Br crystal quality. Herein, additive engineering to the photoactive layer of CsPbI₂Br using the Ti₃C₂T_x MXene nanosheets is reported. Thanks to the improved crystallinity/reduced defect density, together with the formation of the Schottky junction between the MXene nanosheets and CsPbI₂Br, enhanced separation and transfer of the photogenerated electron-hole pairs can be achieved for optimal MXene addition. A simple device configuration of ITO/SnO₂/Ti₃C₂T_x-added CsPbI₂Br/P3HT/Ag can thus deliver a significantly boosted PCE of 15.10%, i.e., a ∼16.69% relative increment compared with that (12.94%) of the control device without adding MXene. In addition, the enhanced humidity resistance is achieved for the MXene-added CsPbI₂Br layers.

Introduction of cadmium chloride additive to improve the performance and stability of perovskite solar cells

With the increase in the importance of using green energy sources to meet the world's energy demands, attempts have been made to push perovskite solar cell technology toward industrialization all around the world. Improving the properties of perovskite materials as the heart of PSCs is one of the methods to fabricate favorable photovoltaic (PV) solar cells based on perovskites. Here, cadmium chloride (CdCl2) was used as an additive source for the perovskite precursor to improve its PV properties. Results indicated CdCl2 improves the perovskite growth and tailors its crystalline properties, suggesting boosted charge transport processes in the bulk and interfaces of the perovskite layer with electron-hole transport layers. Overall, by incorporation of 1.0% into the MAPbI3 layer, a maximum power conversion efficiency of 15.28% was recorded for perovskite-based solar cells, higher than the 12.17% for the control devices. The developed method not only improved the PV performance of devices but also boosted the stability behavior of solar cells due to the passivated domain boundaries and enhanced hydrophobicity in the CdCl2-based devices.