C60-CN: A bifunctional interface modification material for perovskite solar cells

Titanium dioxide (TiO2) is regularly used as an electron transport material in n-i-p perovskite solar cells (PSCs). However, massive defects exist on the TiO2 surface, which will lead to serious hysteresis and interface charge recombination of the device, thus affecting the device's efficiency. In this study, a cyano fullerene pyrrolidine derivative (C60-CN) was synthesized and applied to PSCs for the first time to modify the TiO2 electron transport layer. Systematic studies have shown that the addition of the C60-CN modification layer on the TiO2 surface will enlargement the perovskite grain size, improve the perovskite film quality, enhance electron transport, and reduce charge recombination. The C60-CN layer can significantly reduce the density of trap states in the perovskite solar cells. As a result, the PSCs based on C60-CN/TiO2 obtained a power conversion efficiency (PCE) of 18.60%, suppressing the hysteresis and improving the stability, whereas the PCE of the control device using the original TiO2 ETL was lower, 17.19%.