High open circuit voltage organic solar cells based upon fullerene free bulk heterojunction active layers

Abstract

We have recently reported on a small organic molecule containing a bithiophene core with end-capping phthalimide units (PthTh2Pth) that exhibited a H-aggregation tendency in the solid state and high electron mobility in organic field effect transistors. In this contribution, we have studied both the physical and electrical properties of poly(3-hexylthiophene) (P3HT) and PthTh2Pth thin films by measuring the optical absorption, Frontier molecular orbital energy levels, photoluminescence quenching, thermal properties, and photovoltaic response. Our results have provided a useful insight into the use of PthTh2Pth as an electron acceptor material for organic photovoltaic applications. In comparison with high-performance, fullerene-based, solution-processed bulk heterojunction solar cells reported in the literature, a relatively high open circuit voltage (∼0.94 V) was obtained for various donor–acceptor blend ratios. These results highlight the potential for PthTh2Pth to act as an alternative to fullerenes as acceptors in organic solar cell devices.