New Synthetic Pathway with Improvements and Optoelectronic Applications of 3,5‐Dihexyl‐dithienothiophene (DTT)

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%.