A chlorinated polythiophene-based polymer as a dopant-free hole transport material in perovskite solar cells

Abstract

Despite the remarkable strides made in perovskite solar cell (PSC) research, the incorporation of doped hole transport materials (HTMs) presents a commercialization bottleneck. This study presents a chlorine-substituted polythiophene-based, dioxobenzodithiophene-containing conjugated polymer (P2T-Cl) as a promising dopant-free HTM. The highest occupied molecular orbital of P2T-Cl aligns well with PSCs, and flash-photolysis time-resolved microwave conductivity (TRMC) measurements reveal a high hole transfer yield of 0.99 for P2T-Cl compared to the non-chlorinated analogue of P2T (0.97) and non-doped polytriarylamine (PTAA) (0.79). Consequently, P2T-Cl exhibits a higher power conversion efficiency (PCE) without dopants (15.40%) compared to P2T (15.18%) and the standard polymer HTM PTAA (12.74%). This work presents a compelling example of a dopant-free polymer HTM with a simple structure for PSCs.