Molecular Engineering on Conjugated Side Chain for Polymer Solar Cells with Improved Efficiency and Accessibility

Recent advances in the power conversion efficiency (PCE) of polymer solar cells (PSCs) have demonstrated their potential for alternative photovoltaic technology. Besides photovoltaic performance, material cost and device fabrication process are among the key factors for practical applications. Herein, we report a facile molecular engineering approach with 4-methoxy modified thiophene as the conjugated side chain for polymer donors, which afforded lower highest occupied molecular orbital (HOMO) energy level and enhanced interchain interactions. Therefore, the corresponding PSCs exhibit enhanced open-circuit voltage and PCE compared with the counterparts with thiophene as the conjugated side chain. When fabricated from a nonhalogenated solvent without any additives, over 8% efficiency could be achieved in a representative polymer, PMOT5. Both the synthetic simplicity of materials and high performance from environmentally friendly solvent improve the accessibility of PSCs.