Pd-Free synthesis of dithienothiophene-based oligoaryls for effective hole-transporting materials by optimized Cu-catalyzed annulation and direct C-H arylation

Dithienothiophene (DTT), a versatile building block for pi-conjugated organic materials, has been efficiently synthesized through copper-catalysis with an inexpensive sulfur source in the essential ring-closure/C-S bond formation step, instead of using previously often reported n-butyllithium, costly bis(phenylsulfonyl)sulfide, or palladium-based catalysis. Furthermore, pi-extension from DTT was also achieved step-economically by optimized copper-catalyzed direct C-H arylation reactions, giving three new oligoaryls that were used as effective hole-transporting materials (HTMs) in perovskite solar cells. One of the solar devices demonstrated the highest energy conversion efficiency of 14.67%. For the first time, [Cu]-catalyzed direct C-H/C-I couplings were used as key transformations to access small molecular HTMs.

Automated summary

Dithienothiophene (DTT), a versatile building block, has been synthesized efficiently through copper-catalysis. Pi-extension from DTT was achieved using optimized copper-catalyzed reactions, resulting in new hole-transporting materials for perovskite solar cells. The highest energy conversion efficiency of 14.67% was achieved in one of the solar devices. [Cu]-catalyzed direct C-H/C-I couplings were used as key transformations for accessing small molecular hole-transporting materials for the first time.