A General Low-Temperature Strategy to Prepare High-Quality Metal Sulfides Charge-Transporting Layers for All-Inorganic CsPbI2Br Perovskite Solar Cells

Inorganic perovskite solar cells (I-PSCs) have attracted great attention due to the high thermal stability of inorganic perovskites versus the organic-inorganic perovskites. To ensure the thermal stability of I-PSCs, using effective and stable inorganic charge-transporting layers (CTLs) to replace organic ones is quite desirable. The use of low-temperature-prepared inorganic CTLs can also lower the total cost of I-PSCs. Herein, a general strategy to prepare high-quality inorganic nanoparticles-based electron transport layers (ETLs) below 70 degrees C by ligand exchange on top of inorganic perovskites is developed. The ETLs possess a suitable energy-level structure, favorable conductivity, and chemical stability. Furthermore, all-inorganic CTLs-based CsPbI2Br I-PSCs with p-i-n architecture are fabricated without using any thermally unstable organic components. Consequently, the as-fabricated I-PSCs based on CdS ETLs yielded the highest power conversion efficiency (PCE) of up to 15.04%, among the most efficient CsPbI2Br inverted PSCs. Inspiringly, the unencapsulated all-layer-inorganic PSCs present outstanding stabilities, which maintained 94.8% and 95.2% of their initial PCEs after aging at 85 degrees C in the dark and operating under continuous light illumination at 45 degrees C for 480 h in N-2 atmosphere, respectively.