Heteroatom engineering on spiro-type hole transporting materials for perovskite solar cells

A series of spiro-type hole transporting materials, spiro-OMeTAD, spiro-SMeTAD and spiro-OSMeTAD, with methoxy, methylsulfanyl or half methoxy and half methylsulfanyl terminal groups are designed and prepared. The impact of varied terminal groups on bulk properties, such as photophysical, electro-chemical, thermal, hole extraction, and photovoltaic performance in perovskite solar cells is investigated. It is noted that the terminal groups of the hole transporting material with half methoxy and half methyl-sulfanyl exhibit a better device performance and decreased hysteresis compared with all methoxy or methylsulfanyl counterparts due to better film-forming ability and improved hole extraction capability. Promisingly, the spiro-OSMeTAD also shows comparable performance than high-purity commercial spiro-OMeTAD. Moreover, the highest power conversion efficiency of the optimized device employing spiro-OSMeTAD exceeding 20% has been achieved. CO 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.