Interfacial Modification of NiO_x for Highly Efficient and Stable Inverted Perovskite Solar Cells

Abstract

Nickel oxide is one of the most promising hole‐transporting materials in inverted perovskite solar cells (PSCs) but suffers from undesired reactions with perovskite which leads to limited device performance and stability. Self‐assembled monolayers (SAMs) are demonstrated to effectively optimize the NiOx/perovskite interface, but the significance of the compactness of the SAM at the interface is less investigated. Here, a series of methoxy‐substituted triphenylamine functionalized benzothiadiazole (TBT) based SAM molecules, TBT‐BA, TBT‐FBA, and TBT‐DBA, with benzoic acid, 2‐fluorobenzoic acid and isophthalic acids as anchoring groups are used to modify NiOx. TBT‐BA with the simplest structure is demonstrated to form the densest SAM on NiOx, thus optimized NiOx/SAM/perovskite interface is achieved with enhanced charge collection and suppressed interfacial reaction and recombination. TBT‐BA can also passivate the perovskite most effectively due to the highest binding energy toward perovskite, thus the corresponding inverted PSCs show the highest PCE of 24.8% and maintain 88.7% of the initial PCE after storage at 60 °C for 2635 h in the glovebox. The work provides important insights into designing SAM molecules for modification transporting layers for efficient and stable PSCs.