A new synthesis of dihexyl-DTT using inexpensive CuI and S₈ in the cyclization step is reported. DTT core-based π-extended oligoarenes are fabricated as effective hole-transporting materials (HTM) for inverted perovskite solar cells (iPSC).

Abstract

A new synthetic route to 3,5-dihexyl-dithienothiophene (DTT) and related dithienoheteroaryls was reported. Unlike all existing approaches using costly sulfur-supplying reagents (S-agent), in this work inexpensive and readily available copper salt and elemental sulfur were employed as catalyst and S-agent in the essential cyclization step, in which the reaction parameters were thoroughly optimized, giving targeted DTT in isolated yields up to 86%. Purification was not required after most of steps in this five-step synthesis of dihexyl-DTT. Gram-scale synthesis of dihexyl-DTT was also successfully achieved. Furthermore, π-extension from DTT was facilely carried out either by direct C-H/C-Br couplings or the most succinct cross-dehydrogenative C-H/C-H coupling reactions. The obtained oligoaryls KHC01–04 were fabricated as effective hole-transporting materials (HTM) for inverted perovskite solar cells (iPSC). Solar cell devices utilizing KHC03 as HTM revealed promising power conversion efficiencies of up to 15.27%.