Highly efficient semitransparent CsPbIBr2 perovskite solar cells via low-temperature processed In2S3 as electron-transport-layer

Inorganic perovskite solar cells (IPSCs) with CsPbIBr2 as the light harvester have attracted tremendous attention owing to its thermal stability, low cost and facile manufacture, where electron transport layer (ETL) plays indispensable roles of charge separation, electron transportation and hole-blocking. Although TiO2 is widely used as an ETL, its high-temperature fabrication and low electron mobility hinder the performance and application of IPSCs. Herein, we have proposed a low-temperature (70 °C) chemical bath deposition (CBD) method with different time to prepare In2S3 films as the ETL of IPSCs. By regulating the deposition time of In2S3 films to 85 min, our best-performing device has obtained a high PCE of 5.59% with reduced hysteresis, which is a relative high efficiency for CsPbIBr2 IPSCs by low-temperature fabrication at present. However, the TiO2-based device shows a low efficiency of 5.02% and serious hysteresis. Meanwhile, the In2S3-based devices exhibit improved stability under ambient conditions without encapsulation. Experimental results precisely clarify that this enhanced photovoltaic performance is attributed to the suitable band alignment, low resistance, low recombination of photo-generated carriers at the interface of ETL/perovskite. Promisingly, our low temperature fabricated perovskite and ETL layers might broaden new insights for solution-processed flexible devices.