Naphthalenediimide-based n-type polymer acceptors with pendant twisted perylenediimide units for all-polymer solar cells

Abstract

Polymeric acceptor based all-polymer solar cells have attracted wide interest due to their excellent mechanical properties. In order to combine the advantages of both the polymer and perylenediimide-based small-molecular acceptors, we designed and prepared a series of random copolymers via linking perylenediimide to the polymeric backbone of (naphthalenediimide/quinoxaline)-thieno[3,2-b]thiophene, which were successfully applied as polymer acceptors in solar cells. The effects of the pendant perylenediimide on the optical, electrochemical and photovoltaic performance were tuned via varying ratios of (quinoxaline-perylenediimide2) and naphthalenediimide. Atomic-force microscopic images showed that all random copolymers exhibited significantly improved miscibility with donor compared with an alternating copolymer reference, which coincided with the higher electron mobility measured by the space charge limited current method. The all-polymer solar cell based on the polymeric acceptor with high perylenediimide content achieved a power conversion efficiency of 4.81%. Although there is minimal conjugation between the perylenediimides and main chains, perylenediimides can also contribute to photocurrent generation.