Solvent Engineering of Cs3bi2i9 Perovskite Films for Lead-Free Flexible Semi-Transparent Perovskite Solar Cell Devices with Enhanced Efficiency

Solvent engineering method is very facile approach for the growth of compact perovskite thin films. Herein, we have used solvent engineering approach for the compact and uniform growth of Cs3Bi2I9 using 2-methoxy ethanol (2-ME) additive in N,N-Dimethylformamide (DMF) solvent. We found that 4:1 mixing ratio of DMF:2-ME facilitates compact perovskite films with better crystallinity and enhanced absorbance in comparison to DMF only counterpart. Furthermore, all solution processed semi-transparent lead-free flexible perovskite solar cell devices have been fabricated in regular device architecture and their photovoltaic performance have been compared. Devices fabricated using DMF:2-ME yields power conversion efficiency 1.56%.