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

• Two novel conjugated donor–acceptor polymers were synthesized and characterized.
• By fine tuning side chains, polymers with low lying HOMO and high VOC of 1.02 V were obtained.
• The VOC of the polymer containing 3-hexylthiophene was enhanced without sacrificing the JSC.
• The VOC of 1.02 V is among the highest value for anthracene-based polymer solar cells reported.
• This work exhibits a good way to regulate the molecular energy levels by fine tuning side chains.

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.