Heterocyclic D–A–D hole-transporting material for high-performance inverted perovskite solar cells

Abstract

Small-molecule hole-transporting materials (HTMs) have gained much attention due to their structural flexibility, material properties, and stabilities, allowing for enhanced operational durability in perovskite photovoltaics. We synthesized and investigated a new class of donor–acceptor–donor (D–A–D) configured ligand type hetero-structured small molecule, WWC106, serving as the HTM to enable high-efficiency mixed-halide lead perovskite solar cells. WWC106 is a benzimidazole-centered dopant-free HTM composed of three donors: two 4-methoxy-N-(4-methoxyphenyl)-N-phenylanilines (TPAs) and one 2-(2,2-bis(4-methoxyphenyl)vinyl)-5-methylthiophene. One of the two TPA donors is linked to the benzimidazole via a pyridine unit. Scanning electron microscopy, photoluminescence (PL) time-resolved PL, and space charge limited current measurements on WWC106 HTMs show perovskite formation with good morphology, efficient hole extraction, and hole mobility. The new D–A–D configured WWC106-based device exhibited a high open-circuit voltage of 1.09 V and a high short circuit current density of 20.76 mA cm⁻², with the highest power conversion efficiency of 17.75%.