Controlling Interfacial Hole Tunneling To Mitigate Reverse-Bias Breakdown in Perovskite Solar Cells

Abstract

Reverse-bias degradation, including local shunting and hot spot formation, remains a critical obstacle to the operation of perovskite solar cells (PSCs). Here, we introduce a TiO2 hole blocking layer (HBL) between the SnO2 electron transporting layer and fluorine-doped tin oxide electrode to suppress reverse-bias-induced hole injection and leakage current. Combined with conformal SnO2 chemical bath deposition (CBD), the TiO2 HBL increases the breakdown voltage beyond –10 V and mitigates local shunt formation and thermal degradation, as confirmed by conductive atomic force microscopy and thermal imaging. Time-resolved photoluminescence (TRPL) analysis further reveals enhanced interfacial charge extraction and reduced trap-assisted recombination. Consequently, HBL-containing PSCs show improved reverse-bias recovery and increased power conversion efficiency from 23.47% to 23.88% for nanoparticle-SnO2 devices and from 25.81% to 26.22% for CBD SnO2 devices.