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.