Unravelling the Correlation between Charge Mobility and Cocrystallization in Rod–Rod Block Copolymers for High-Performance Field-Effect Transistors

Cocrystallization involving two or more components aggregating into cocrystals allows the preparation of materials with markedly improved charge mobility. This approach however, is little explored in all-conjugated block copolymers (BCPs). Herein, we report the first investigation into the correlation between cocrystals and charge mobility in a series of new all-conjugated BCPs: poly(3-butylthiophene)-b-poly(3-hexylselenophene) (P3BT-b-P3HS) for high-performance field-effect transistors. These rationally synthesized rod–rod BCPs self-assemble into cocrystals with high charge mobilities. Upon one-step thermal annealing, their charge mobilities decrease slightly despite their increased crystallinities. After two-step thermal annealing, P3BT-b-P3HS (P3BT/P3HS=2:1) and (1:1) cocrystals disappear and phase separation occurs, leading to greatly decreased charge mobilities. In contrast, P3BT-b-P3HS (1:2) retains its cocrystalline structure and its charge mobility.