A Novel Benzo[1,2-<i>b</i>:4,5-<i>b</i>′]dithiophene-Based Conjugated Polymer with a Pendant Diketopyrrolopyrrole Unit for High-Performance Solar Cells

Abstract

A novel conjugated polymer of PBDT-TDPP-S was synthesized, which contains a donor unit of benzo[1,2-b:4,5-b′]dithiophene in main chain and an acceptor unit of diketopyrrolopyrrole in side chain. This kind of side-chain donor–acceptor (D–A) polymer exhibited better solution processability, lower HOMO level (−5.34 eV), and more balanced carrier mobility relative to its corresponding main-chain D–A conjugated polymers. Using PBDT-TDPP-S as electron donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as electron acceptor, the resulting polymer solar cells exhibited outstanding photovoltaic properties with a power conversion efficiency of 4.89%, an open-circuit voltage of 0.84 V, a short-circuit current of 10.04 mA cm–2, and a fill factor of 56.0%.