Significant efficiency enhancement of carbon-based CsPbI 2 Br perovskite solar cells enabled by optimizing tin oxide electron transport layer

Carbon-based perovskite solar cells (C-PSCs) have been popular for achieving low-cost and stable photovoltaics. To overcome an obstacle of high-temperature annealing process for producing titanium dioxide (TiO 2 ), CsPbI 2 Br C-PSCs based on a device structure of FTO/tin oxide (SnO 2 )/CsPbI 2 Br/carbon electrode can be fabricated at the low-temperature annealing process of 280 °C for 180 s, where SnO 2 is used as the electron transporting layer (ETL). Experimental results showed that the suitable concentration of SnO 2 ETL could yield smooth surface CsPbI 2 Br films with free-pinhole and larger grain-sized crystallization. In combination with prolonging annealing time, a champion power conversion efficiency of 9.68% with a larger open-circuit voltage ( V oc ) of 1.14 V was obtained for CsPbI 2 Br C-PSC based on SnO 2 ETL. Here, a simple low-temperature fabricating process of SnO 2 ETL can be adapted to flexible substrates for C-PSCs and furtherly reduce the manufacturing cost.