Localized Oxidation Embellishing Strategy Enables High-Performance Perovskite Solar Cells

Perovskite solar cell (pero-SC) has attracted extensive studies as a promising photovoltaic technology, wherein the electron extraction and transfer exhibit pivotal effect to the device performance. The planar SnO₂ electron transport layer (ETL) has contributed the recent record power conversion efficiency (PCE) of the pero-SCs, yet still suffers from surface defects of SnO₂ nanoparticles which brings energy loss and phase instability. Herein, we report a localized oxidation embellishing (LOE) strategy by applying (NH₄)₂CrO₄ on the SnO₂ ETL. The LOE strategy builds up plentiful nano-heterojunctions of p-Cr₂O₃/n-SnO₂ and the nano-heterojunctions compensate the surface defects and realize benign energy alignment, which reduces surface non-radiative recombination and voltage loss of the pero-SCs. Meanwhile, the decrease of lattice mismatch released the lattice distortion and eliminated tensile stress, contributing to better stability of the devices. The pero-SCs based on α-FAPbI₃ with the SnO₂ ETL treated by the LOE strategy realized a PCE of 25.72 % (certified as 25.41 %), along with eminent stability performance of T₉₀>700 h. This work provides a brand-new view for defect modification of SnO₂ electron transport layer.