Effective side chain selection for enhanced open circuit voltage of polymer solar cells based on 2D-conjugated anthracene derivatives

Abstract

Two novel conjugated donor–acceptor polymers were synthesized by combining anthracene donor and benzothiadiazole acceptor with two different side chains (conjugated and non-conjugated). Their absorption spectroscopy, thermogravimetric analysis, electrochemical cyclic voltammetry, theoretical prediction, surface morphology, and photovoltaic performance were investigated. The resultant two-dimensional configuration showed good optical and electrochemical properties. By selectively introducing branched conjugated side chains and non-conjugated linear side chains on the polymer back-bone, the highest occupied molecular orbital levels are low lying which results in an increased open circuit voltage for polymer solar cells. The open circuit voltage of 1.02 V in this work was among the highest value for anthracene-based polymer solar cells ever. Our results suggest a good way to regulate the molecular energy levels by selecting appropriate side chains.