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.