Benzo[d][1,2,3]thiadiazole (isoBT): Synthesis, Structural Analysis, and Implementation in Semiconducting Polymers

Benzo[d][2,1,3]thiadiazole (BT) is a markedly electron-deficient heterocycle widely employed in the realization of organic semiconductors for applications spanning transistors, solar cells, photodetectors, and thermoelectrics. In this contribution, we implement the corresponding isomer, benzo[d][1,2,3]thiadiazole (isoBT), along with new 6-fluoro-isoBT and 5,6-difluoro-isoBT units as synthons for constructing alternating copolymers with tetrathiophene (P1–P3). New isoBT-based small molecules as well as the corresponding BT-quaterthiophene based polymers (P4–P6) are synthesized and characterized to probe architectural, electronic structural, and device performance differences between the two families. The results demonstrate that isoBT complements BT in enabling high-performance optoelectronic semiconductors with P3 exhibiting hole mobilities surpassing 0.7 cm2/(V s) in field-effect transistors and power conversion efficiencies of 9% in bulk-heterojunction solar cells.