Additive Combining Passivator for Inverted Wide‐Bandgap Perovskite Solar Cells with 22% Efficiency and Reduced Voltage Loss

Abstract

Wide‐bandgap (WBG) perovskite solar cells (PSCs) play a crucial role in tandem devices. However, the severe nonradiative recombination that occurs at the interface between perovskite and electron transport layer (ETL) leads to excessive open‐circuit voltage (VOC) loss, which hinders the further improvement of the photovoltaic conversion efficiency (PCE). To mitigate the VOC loss in WBG PSCs, the defects in grains and grain boundaries are reduced as well as the energy‐level alignment between perovskite layer and ETL, so as to improve the carrier collection efficiency, is optimized. Herein, potassium thiocyanate is introduced as an additive and 2‐thiophenethylammonium bromide (TEABr) is used to passivate perovskite/C60 interface. The synergistic treatment reduces the defect density and prolongs the carrier lifetime, implying that nonradiative recombination is effectively suppressed. Meanwhile, the energy‐level alignment of the perovskite and C60 is optimized, leading to the improvement of VOC. Finally, WBG PSCs with a bandgap of 1.68 eV achieve a VOC of 1.22 V (with a VOC loss of 0.46 V) and a PCE of 22.02%.