Semi-crystalline Random Conjugated Copolymers with Panchromatic Absorption for Highly Efficient Polymer Solar Cells

Abstract

Extension of the light absorption range of the conjugated polymer is one of the most important factors for enhancement of power conversion efficiency of polymer solar cells (PSCs) because the limited absorption of most conjugated polymers leads to lower current density. An effective approach to extend light absorption range is synthesis of copolymers composed of at least two different chromophores with complementary absorption range. To broaden the light absorption range and thus to enhance the performance of PSCs, we synthesized random conjugated copolymers consisting of DPP and isoindigo as co-electron deficient units in donor-acceptor type copolymer. The random copolymers exhibited both broad light absorption and low-lying HOMO levels. Furthermore, the predominant face-on orientation of the random copolymers on the substrate is beneficial for charge transport in the device. Combination of excellent optoelectrical properties and favorable molecular orientation renders this random copolymer a promising candidate for active layer material in PSCs