四旋翼NFA小分子端基变化对光电性能影响的理论研究

he ternary blending strategy, where a third component is introduced into binary organic solar cells (OSCs) to optimize the active layer morphology and photovoltaic properties, is commonly used to enhance the photoelectric conversion efficiency of OSCs. Non-fullerene acceptor (NFA) small molecules of the A2-A1-D-A1-A2 type, as an important branch of NFAs, have received particular attention in ternary OSC systems in recent years. In particular, a non-planarfour-bladed propellers A2-A1-D-A1-A2 type NFA small molecule, SF-BTA1, SF-BTA2, and SF-BTA3, has demonstrated outstanding photovoltaic performance in the PM6:Y6 binary system. The subtle end-group differences in these molecules significantly affect the performance of ternary OSCs, especially SF-BTA1 with the rhodanine end-group. However, theoretical research on how end-group changes affect the performance of these four-rotor NFAs is still in its infancy. This study selected SF-BTA1, SF-BTA2, and SF-BTA3 as the research objects and applied Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TDDFT) to conduct an in-depth theoretical analysis of their ground and excited state properties, in order to reveal the specific impact of end-group changes on the molecular photovoltaic properties. It is found that the computational results are in good agreement with the experiments. Specifically,the exciton binding energies of these three molecules are comparable, while SF-BTA1 has the smallest singlet-triplet energy gap, indicating that the rhodanine end-group may help reduce charge loss in four-rotor small molecules. Therefore, further structural modifications based on SF-BTA1 are expected to develop even better third-component materials.