Effective Regulation of Photovoltaic Performance of Organic Solar Cells by External Electric Field: A Comprehensive Theoretical Study

Improving the performance of organic solar cells (OSCs) has emerged as a central research focus within organic photovoltaics in recent years. Applying an external electric field (<b><i>F</i></b>_ext) to the photoactive layer in organic solar cells (OSCs) is an effective strategy to enhance device performance. Compared with conventional chemical modification techniques, this method offers advantages, such as tunability and reversibility. However, studies on its underlying microregulatory mechanisms remain limited. This study theoretically investigated the influence of <b><i>F</i></b>_ext on charge transfer and transport rate in the 4,4'-(9<i>H</i>-fluorene-9,9-diyl)bis(<i>N</i>,<i>N</i>-diphenylaniline):(1,3,5-triazine-2,4,6-triyl)tris(benzene-3,1-diyl)tris(diphenylphosphine oxide) (DTF:PO-T2T) system. The results reveal that <b><i>F</i></b>_ext mainly enhances the charge transfer rate by modulating the reorganization energy and further improves charge transport by affecting the electron and hole transfer integrals. Finally, parameters relevant to experimental characterization were theoretically evaluated. The results demonstrate that <b><i>F</i></b>_ext exerts a substantial influence on the power conversion efficiency (PCE). When <b><i>F</i></b>_ext = 3 × 10^-5 au, the competitive relationship between open-circuit voltage (<i>V</i>_OC) and short-circuit current density (<i>J</i>_SC) can be effectively balanced, thereby maximizing the PCE. This work offers theoretical insights and optimization strategies for achieving high-performance OSCs.