Triarylamine-Functionalized Imidazolyl-Capped Bithiophene Hole Transporting Material for Cost-Effective Perovskite Solar Cells

Triarylamine end-capped-functionalized arylene-imidazole derivatives were synthesized from readily accessible, inexpensive precursors and employed as hole transporting materials (HTMs) in perovskite solar cells (PSCs). All the HTMs displayed high thermal decomposition temperatures (>410 degrees C), which is beneficial for realizing stable PSC devices. In addition, the new HTMs show appropriate energy level alignment with the perovskite layer, ensuring efficient hole transfer from perovskites to HTMs. Interestingly, PSCs fabricated with the triarylamine-functionalized imidazolyl-capped bithiophene molecule (DImBT-4D) as the HTM exhibited the best power conversion efficiency of 20.11%, comparable to that of the benchmark HTM spiro-OMeTAD, prompting it be a prospective candidate for large-scale PSC applications.