Significantly improved photovoltaic performance of the triangular-spiral TPA(DPP-PN)3 by appending planar phenanthrene units into the molecular terminals

Abstract

A novel triangular-spiral conjugation molecule of TPA(DPP-PN)3 using triphenylamine (TPA) as the donor core, diketopyrrolopyrrole (DPP) as the acceptor arm and phenanthrene (PN) as the planar arene terminal, as well as its counterpart of TPA-3DPP without the PN terminal, were prepared. Their UV-vis absorption, electrochemistry and thermal stability, as well as hole mobility were investigated. Significantly red-shifted UV-vis absorption profiles were observed for TPA(DPP-PN)3 instead of TPA-3DPP in solution and solid state. A hole mobility of 1.67 × 10-4 cm2 V-1 s-1 was obtained for the TPA(DPP-PN)3/PC71BM blended film, which is 2.1 times higher than that of the TPA-3DPP/PC71BM blended film. Furthermore, the TPA(DPP-PN)3/PC71BM-based organic solar cells presented better photovoltaic property with a maximum power conversion efficiency of 3.67%, which is 1.9 times higher than that of TPA-3DPP/PC71BM-based devices. The results confirm that appending planar PN terminals to TPA-3DPP with a triangular-spiral shape is an efficient approach to improve the photovoltaic performance of its resulting molecules.