From Macroscopic to Nanoscopic Current Hysteresis Suppressed by Fullerene in Perovskite Solar Cells

Abstract

In perovskite solar cells (PSCs), hybrid perovskite:fullerene phases are proposed to suppress macroscopic current hysteresis behavior by alleviating ion migration. However, the understanding of how fullerenes exactly alleviate the current hysteresis and what is the influence of fullerenes in such hybrid phases are still unclear from a microscopic viewpoint. Herein, the intentional incorporation of fullerene into perovskite is used to examine how fullerene exactly reduces the macroscopic current hysteresis. The location and distribution of fullerenes in the hybrid phase are confirmedly visualized using conductive atomic force microscopy and Kelvin probe force microscopy measurements. Fullerenes located at grain boundaries function as a source of beneficial effect on choking the channels of ion migration and also as the electron traps that compromise the photocarrier extraction. Macroscopic current hysteresis originating from the influxes of all nanoscopic grain boundary current signals is avoided in PSCs based on the hybrid perovskite:fullerene phases. These results not only provide a strong correlation between nanoscopic and macroscopic current hysteresis behaviors but also clearly clarify how fullerenes play a role in reducing the current hysteresis in hybrid phases and thus prototype devices.