New polymer acceptors for organic solar cells: the effect of regio-regularity and device configuration

Two polymers, r-PDI-diTh and i-PDI-diTh, were synthesized as acceptors applicable for solution-processed BHJ OSCs. By introducing a bulky, dove tailed side chain and thereby suppressing the π–π interactions between perylenediimide units in the backbones of acceptor polymers, more effective phase segregation of these acceptors with a donor polymer (P3HT) was realized. By employing the inverted device configuration to better match the vertical phase separation of donor–acceptor polymers produced by solution processing, undesirable polaron pair recombination was suppressed, and PCE up to 2.17% was achieved from the regio-regular acceptor r-PDI-diTh.