Non-adiabatic Dynamical Simulations to the Radiative and Non-radiative Recombinations of the Non-fullerene Acceptor Excited State To Optimize Its Photoluminescence Quantum Yield

Optimizing the photoluminescence quantum yield (PLQY) of non-fullerene acceptor (NFA) molecules is critical for reducing the non-radiative recombination energy loss in NFA-based organic solar cells. In this letter, by developing a non-adiabatic dynamical method combined with different electron population rate equations, we separately simulate the radiative and non-radiative recombination process of the NFA molecular excited state, and thus clarify the quantitative correlations of typical characteristics of NFA molecules with their PLQY, including the analyses for the corresponding mechanisms directed against the conventional "energy gap law". The main findings include: weakening the intramolecular electron-phonon coupling and electronic push-pull potential can optimize the competition between radiative and non-radiative recombinations, thus improving PLQY; furthermore, increasing the intermolecular J-aggregation ratio should be an effective strategy to alleviate the aggregation-induced reduction in PLQY. These findings provide clear directions for the rational design of NFA molecules and morphology optimization toward a higher PLQY.