Enhanced crystalline morphology of a ladder-type polymer bulk-heterojunction device by blade-coating

A blade-coating process was employed to fabricate bulk-heterojunction (BHJ) polymer solar cells based on a ladder-type polymer (PIDT-PhanQ) with low crystallinity. Compared to the devices processed by a conventional spin-coating method, an intriguing morphology with enhanced phase-separation and increased crystallinity was achieved. As a result, power conversion efficiency up to 7.25% could be achieved from the blade-coated PIDT-PhanQ:PC71BM BHJ film, surpassing the original value obtained by spin-coating (6.29%). This improved photovoltaic performance is attributed to the improved charge carrier mobilities, which correlates well with the increased crystallinity and the organized network of the donor-acceptor phases that produce efficient charge-transporting pathways.