Dual-functional passivators for highly efficient and hydrophobic FA-based perovskite solar cells

Ionic defects and humidity instability are the main limitations to realize the commercialization of FA-based perovskite solar cells. To overcome these issues, here, we report a dual-functional molecular 2-Fluorothiophenol (FTP) to achieve high-quality FA-based perovskites with simultaneously efficient defects passivation and improved hydrophobicity. It is revealed that SH- groups of FTP induce highly oriented crystallization toward (001) crystal plane of cubic-phase Cs(0.05)FA(0.95)PbI(3) perovskite structure, thus improving the charge carrier transport. Moreover, a strong Lewis acid-base interaction between the SH- group and Pb2+ in perovskite is of great benefit to passivate the surface and grain boundary defects, with additional merit for improving humidity stability of the FA-based perovskite films in conjunction with the hydrophobic group of FTP. The introduction of FTP boosts the efficiency from 20.30% to 22.66% for 0.04 cm(2) solar cells and from 16.86% to 20.01% for 1.0 cm(2) devices. More importantly, the solar cells demonstrate excellent humidity stability, which can retain 90% of their original efficiency after being kept for 80 days under ambient air conditions.

Automated summary

This study reports the use of a dual-functional molecular 2-Fluorothiophenol (FTP) to address the issues of ionic defects and humidity instability in FA-based perovskite solar cells. The results show that FTP can passivate defects and improve humidity stability, leading to an increase in solar cell efficiency. This research provides important technical support for the commercialization of FA-based perovskite solar cells.