Synthesis of Polythiophene with a Photo-Crosslinkable Side Chain

We have synthesized a photo-crosslinkable polythiophene copolymer functionalized with a cinnamate moiety to improve the stability of organic photovoltaic (OPV) cells. The active layer of OPV cells is generally bulk heterojunction (BHJ) that consists of two or more organic semiconductors. When BHJ forms a micro-phase-separated structure with a blend of two organic materials, its structure inclines to change into a macro-phase-separated one after some time. To stabilize the BHJ morphology, we used a crosslinkable polymer containing a cinnamate moiety. The copolymer film became insoluble after UV irradiation because of [2+2] dimerization of the cinnamate groups.