Synthesis, characterization and photovoltaic properties of three new 3,4-dithienyl-substituted polythiophene derivatives

Abstract

Three 3,4-dithienyl-substituted polythiophene derivatives have been synthesized and characterized. Polymer P2 exhibits the widest light absorption spectrum of the polymers in its polymer chain, which has an alternative donor-acceptor structure. Copolymers blended with 6,6-phenyl-C71-butyric acid methyl ester(PC71BM) as active layers are used to fabricate polymer solar cells (PSCs), and a variety of post-treatments are employed to optimize the PSCs performance. A maximum power conversion efficiency (PCE) of 1.22% is achieved for the conventional configuration device based on P2, and the inverted configuration device of P2 is also prepared for comparison. The results show that the inverted P2 device exhibits a better PCE (1.47%) than that of the conventional device due to the TiO2 nanoparticles and the close energy alignment between the work function of the MoO3 and the HOMO energy levels, which facilitate a light absorption increase and improved charge transport. Three new copolymers P1, P2, P3 have been synthesized and characterized. A variety of post-treatments are employed to optimize the performance of solar cells based on these copolymers. A maximum power conversion efficiency (PCE) of 1.22% is achieved by P2 in conventional configuration cells. The PCE of P2 can be further enhanced with inverted configuration, which is ascribe to the more light absorption by TiO2 nanoparticles and the close energy alignment between the work function of MoO3 and the HOMO energy levels of P2.