Understanding Interface Engineering for High‐Performance Fullerene/Perovskite Planar Heterojunction Solar Cells

TLDR

Interface engineering is critical for efficient solar cells, but the interface between a metal electrode and ETL remains poorly understood. The authors examined the metal–ETL interface with electrical measurements and KPFM, revealing a uniform work‑function decrease induced by the fulleropyrrolidine interlayer. Inserting a fulleropyrrolidine interlayer between the silver electrode and ETL doubled the PCE from 7.5 % to 15.5 %, increased recombination resistance, electron extraction, and carrier lifetime, and the devices remained stable in ambient air.

Abstract

Interface engineering is critical for achieving efficient solar cells, yet a comprehensive understanding of the interface between a metal electrode and electron transport layer (ETL) is lacking. Here, a significant power conversion efficiency (PCE) improvement of fullerene/perovskite planar heterojunction solar cells from 7.5% to 15.5% is shown by inserting a fulleropyrrolidine interlayer between the silver electrode and ETL. The interface between the metal electrode and ETL is carefully examined using a variety of electrical and surface potential techniques. Electrochemical impedance spectroscopy (EIS) measurements demonstrate that the interlayer enhances recombination resistance, increases electron extraction rate, and prolongs free carrier lifetime. Kelvin probe force microscopy (KPFM) is used to map the surface potential of the metal electrode and it indicates a uniform and continuous work function decrease in the presence of the fulleropyrrolidine interlayer. Additionally, the planar heterojunction fullerene/perovskite solar cells are shown to have good stability under ambient conditions.