Extended Conjugation and End-Group Modification of Silicon-Bridged Carbazole-Based Non-Fullerene Acceptors in Indoor Organic Photovoltaics

In this work, the strategies of extended conjugation and end-group modification are used to design four non-fullerene acceptors, DTTSiC-2F, DTTSiC-2Cl, DTTSiC-4F, and DTTSiC-4Cl. To investigate the influence of extended conjugation and end-group modification, grazing-incidence wide-angle X-ray scattering is used to analyze the packing alignment of the molecules. Photovoltaic performances under both AM 1.5G and indoor conditions are examined. Owing to the push-pull effect, DTTSiC-2F and DTTSiC-2Cl manifest a much higher lowest unoccupied molecular orbital, resulting in higher V_OC. DTTSiC-4F and DTTSiC-4Cl manifest higher J_SC due to the red-shifted and stronger absorption. Under indoor conditions, devices based on PM6:DTTSiC-4Cl exhibit a power conversion efficiency of 19.18% with a V_OC of 0.79 V, a J_SC of 92.15 μA/cm², and an FF of 73.21%, proving that extended conjugation and end-group modification are particularly promising strategies for developing indoor organic photovoltaics.