3,5-Difluorophenylboronic acid-modified SnO2 as ETLs for perovskite solar cells: PCE > 22.3%, T82 > 3000 h

SnO2 has recently emerged as a promising Electron transportation layer (ETL) for perovskite solar cells (PeroSCs). However, its inherent trap-states usually cause charge recombination, and its conductive band does not match well with that of the perovskite film. In order to solve these problems, we herein employed 3,5-Difluorophenylboronic acid (denoted by FPBA) to modify SnO2. After modification, the trap state density of SnO2 is drastically reduced, and better energy-level alignment is formed with perovskite owing to the interfacial dipole of FPBA. Consequently, the champion Power conversion efficiency (PCE) of Pero-SCs is increased from 20.38% to 22.36% after SnO2 being modified with FPBA. Moreover, the unencapsulated device based on FPBA-modified SnO2 maintains 82% of the initial PCE after being stored in nitrogen atmosphere for more than 3000 h.

Automated summary

By modifying SnO2 with FPBA, the trap state density of SnO2 was significantly reduced and better energy-level alignment was achieved, leading to an increased power conversion efficiency of perovskite solar cells. Additionally, the FPBA-modified SnO2-based unencapsulated device showed good stability with over 82% of initial PCE retained after long-term storage.