Bandgap Engineering of Dual Acceptor-Containing Naphthalene Diimide Polymers for All-Polymer Solar Cells

Naphthalene diimide (NDI)-based polymers, as nonfullerene acceptors for all-polymer solar cells (all-PSCs), are usually investigated by manipulating electron donating units, which have a narrow bandgap showing absorption spectra mostly overlapping with high-performance donor polymers like PTB7-Th. In order to gain complementary absorptions between NDI-based polymers and PTB7-Th, we report three NDI-based polymers (P1-P3) designed by a dual-acceptor strategy and systematically study their effect on the bandgap, molecular configuration, and charge transport property. The absorption bands of these polymers range from 300 to 800 nm; in particular, P1 with a maximum absorption at 530 nm exhibits a good complementary absorption with the PTB7-Th. The device based on the PTB7-Th:P1 blend provides higher J(sc) and efficiency than those based on other two polymers. The result suggests that the dual-acceptor strategy is effective to design acceptor polymers with adjustable absorption and molecular configuration for the all-PSCs.