Fine-tuning of the inner sidechain of donor polymers for efficient indoor organic photovoltaics

Recently, the performance of organic photovoltaics (OPVs) has increased with the advent of non-fullerene acceptors, and significant efforts have been devoted to improving the performance via the side-chain engineering of Y6 and its derivatives. However, research on optimizing indoor OPVs by modulating the side chains of polymer donors has seldom been conducted. Here, we intend to optimize the indoor performance of OPVs by substituting 3,7-dimethyl octane with PBDB-EH-3Cl (PM7), which has previously shown the highest power conversion efficiency (PCE). The optoelectrical, morphological, and electrochemical properties of the PM7 polymer donor were controlled by fine-tuning the inner alkyl side chain of PM7. Hence, the optimized OPVs exhibited an excellent PCE of 28.9% under a light emitting diode (LED) 1000 lx lamp and a maximum output power density of 359.7 mu W cm(-2) under a halogen 1000 lx lamp, which can be attributed to the effectively suppressed charge recombination, high crystallinity, and suitable surface morphology.