High-PerformancePolymer Solar Cells Based on Blue-Light-EmittingPolyfluorene Derivative-Doped Systems

The polymer solar cells (PSCs) have received a lot of research attention owing to their commendable qualities. However, the insufficient photoelectric conversion efficiency restricts their application and popularization, among which the existing problems can be summarized as low optical absorption leading to low spectral utilization of the device and the charge transfer obstructed due to energy level mismatch. Therefore, broadening the light absorption range of the active layer and promoting carrier transmission are the keys to improving the device performance. We synthesized blue polyfluorene derivatives containing a phenoxazine unit (PF-PO) and introduced in a PSC system based on PM6:IT-4F blends to improve the absorbance and improve the exciton dissociation efficiency and balanced charge carrier mobility. The power conversion efficiency (PCE) of the device improved from 12.64% when undoped to 13.97% after doping with PF-PO. The short-circuit density (<i>J</i>_SC) is improved from 21.23 to 22.47 mA/cm², and the fill factor (FF) is improved from 70.31 to 73.16%, which is the main factor for the improvement of device efficiency. These findings suggest that incorporating doping into the device is a highly effective method for improving the photovoltaic performance of the material.