Efficiency enhancement of polymer photovoltaic devices using thieno-thiophene based copolymers as nucleating agents for polythiophene crystallization

Abstract

A copolymer including thieno-thiophene units (DHPT3) has been synthesized and used as crystallization nucleating agent in the active layer of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) bulk heterojunction photovoltaic devices. We demonstrate in this work that the addition of DHPT3 in P3HT/PCBM thin films induces a marked structural ordering of the polythiophene phase. This structural order enhances the charge carrier transport properties and enlarges the active layer absorption spectrum. The photovoltaic devices power conversion efficiency prior to thermal annealing could be enhanced by a factor of 2 by adding 5% of DHPT3 into the blend.