Polymerizable Ammonium Salt Interlayer for Efficient and Stable NiOx-Based Perovskite Solar Cells

Abstract

Although the research of formal perovskite solar cells (PSCs) has achieved great breakthroughs, the use of doped small-molecule organic hole transport layers limits the improvement of stability. PSCs with an inverted form show great potential in a more stable device structure. In this paper, a NiOx/3D perovskite interface in inverted PSCs was modified with a polymerizable amine salt (2-methylallylamine hydroiodide (CTBAI)) interlayer. The double bonds contained in CTBAI thermally induced polymerization of a thin film after heat treatment, resulting in the formation of amine salts with longer molecular chains. The modified layer can improve crystallinity and reduce defects in the film, as well as optimize the interface energy level and reduce interface recombination. The efficiency of NiOx-based inverted PSCs based on the optimized interface increased from 17.0% to 18.2%. After 280 h of MPP testing, the encapsulated device tested in ambient air (RH = 50–60%) demonstrated a robust light stabilization and maintained over 93% efficiency.