Regulating simple π-bridges of Y-series polymer acceptor enables various High-Performance All-Polymer photodetectors

All-polymer optoelectronic devices have drawn extensive attention recently due to their outstanding thermal and mechanical stabilities. As one of the most promising acceptors, Y-series polymer have been widely utilized in allpolymer solar cells, but their applications in all-polymer photodetectors (all-PPDs) are rarely reported. Hence, developing a high-performance Y-series polymer acceptor with excellent universality for all-PPDs is urgently needed. Herein, we presented four polymer acceptors, P1-P4, by polymerizing Y-series small molecules with thiophene, bithiophene, difluoro-bithiophene, and thienothiophene pi-bridges, respectively. Benefiting from improving the molecular symmetry without introducing disordered single bonds, P4 exhibited fine molecular stacking and orientation in the film state compared with P1-P3. Moreover, owing to the large torsion angle between thienothiophene and the end group of Y-unit, P4 displayed a more suitable aggregation behavior in the solution state, which gives P4 excellent miscibility with various donors. As a result, J71:P4 devices achieved remarkable specific detectivity of 1.4 x 1014 Jones at - 0.1 V, which is the highest detectivity reported for allPPDs, as well as 1.3 x 1014 Jones for PM6:P4 devices and 8.0 x 1013 Jones for PTB7-Th:P4 devices. This work indicates that high-performance Y-series polymer acceptors with excellent universality can be realized by changing pi-bridge units, which may accelerate the commercialization of all-PPDs.