Photocationic Initiator Induced Synergy for High-Performance Perovskite Solar Cells

Abstract

The perovskite structures are prone to decomposition due to the formation of defect sites under various stressors. As a result, the stability of perovskite materials has been an Achilles’ heel in actual commercialization. Herein, photocationic initiator based on 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (TPFB) is introduced into perovskite film through the antisolvent process to enhance the efficiency and stability of perovskite solar cells. The hypervalent iodine part serves as a Lewis acid to passivate the negatively charged defects, while the pentafluorophenyl borate part is used to tailor the crystallization process by forming strong hydrogen bonding. Furthermore, the superior hydrophobicity of TPFB insulates the perovskite films. The resulted MAPbI3 devices show maximum power conversion efficiency (PCE) reaching 20.41% and ultrahigh open voltage (Voc) up to 1.15 V with the remaining 85% efficiency after 1000 h shelf storage. Furthermore, by introducing TPFB through a simple posttreatment process, the device delivers a PCE of 23.4% (steady-state PCE of 23.2%), features useful for advanced double cation-based perovskite device. In sum, these findings develop a universal passivation strategy and open a novel field of Lewis acid-based passivation agent.