Morphology manipulation of photoactive layer through block copolymer to improve the photovoltaic performances of polymer solar cells

Abstract

Additive treatment is an effective method for manipulating the bulk heterojunction (BHJ) photoactive layer morphology of polymer solar cells (PSCs). In this work, block copolymer, polystyrene-block-poly(acrylic acid) (PS-b-PAA), was elaborately selected (according to Flory–Huggins theory) as an additive for active layer to manipulate the BHJ morphology and to enhance the photovoltaic performance of devices. As results, with a PS-b-PAA concentration of 0.4 mg/ml, the corresponding devices achieve a significant power conversion efficiency (PCE) improvement to 13.08%. By systematically analysis, the improved PCE can be ascribed to more appreciate phase separation induced by incorporation of PS-b-PAA. For the instance of the photovoltaic physical process, more suitable morphology can induce improved charge transport efficiency, suppressed bimolecular recombination and monomolecular recombination or trap-assisted recombination. In comparing, the photovoltaic performance of devices with PS-b-PAA is obviously better than that of devices with insulating polymer polystyrene (PS) and polyacrylic acid (PAA). Hence, this work checks the morphology manipulation effects of block copolymer PS-b-PAA and provides an effective and facile method to improve the morphology and photovoltaic performances of PSCs.