Sulfur-Rich Benzodithieno[3,2-B]Thiophene-Cored Hole Transporting Materials For Long-Time Stability Of Perovskite Solar Cells

Two novel benzodithieno [3,2-b]thiophene-cored hole-transporting materials (HTMs), DTmBDT-TPA and DTmBDT-OMeTPA were synthesized and their thermal, photophysical, and electrochemical characteristics were systematically investigated. The devices based on DTmBDT-TPA and DTmBDT-OMeTPA exhibited power conversion efficiencies of 16.62% and 18.22%, respectively. The S atoms in thiophene moieties were involved in the passivation interaction with perovskite; accordingly, the long-term stabilities of both DTmBDT-based perovskite solar cells (PSCs) were superior to that of the 2,2 ',7,7 '-tetrakis (N,N-di-p-methoxyphenylamine)-9,9 '-spirobifluorene (spiro-OMeTAD)-based PSC. After 1440 h storage, the unencapsulated DTmBDT-TPA- and DTmBDTOMeTPA-based PSCs retained over 81% and 90% of their initial efficiencies, respectively; whereas, the spiroOMeTAD device lost approximately 50% of its original efficiency. These results show that DTmBDT-based compounds are promising HTMs for constructing high-stability PSCs.