Influence of molecular weight on the solar cell performance of double-crystalline donor-acceptor block copolymers

We investigate the influence of the molecular weight of double-crystalline donor-acceptor block copolymers comprised of poly(3-hexylthiophene) as donor and poly(perylene bisimide acrylate) as acceptor segments on the device performance of polymer solar cells. Two block copolymers 1 and 2 exhibiting different molecular weights but the same composition are compared. Block copolymer 2 with the higher molecular weight shows an improvement in the hole carrier mobility mu(OFET) of more than two orders of magnitude, and an improvement in the external quantum efficiency of one order of magnitude reaching 31%, which is the highest reported value for a block copolymer system.