Semitransparent Organic Solar Cells with Efficiency Surpassing 15%

Semitransparent organic solar cells (ST-OSCs) have promising prospects for building or vehicle integrated solar energy harvesting with energy generation and see-through function. How to achieve both an adequate average visible transmittance (AVT) and high-power conversion efficiency (PCE) is always the key issue. Herein, a simple but effective strategy for constructing high performance ST-OSCs by introducing a small molecule [2-(9-H-Carbazol-9-yl) ethyl] phosphonic acid (2PACz) into a low-donor content active layer is reported. The fill factor is improved from 70.5% to 75.5% and correlated to the mitigated charge recombination and strengthened charge extraction, further ascribed to the enhanced build-in potential, reduced charge transport resistance, and favorable film morphology. By combining the unique nature of 2PACz, that can spontaneously form in situ self-organized hole transport interlayers under bulk-heterojunction films, PEDOT-free ST-OSCs with a PCE of 15.2%, amongst the highest values in this field, is achieved with an AVT of 19.2%. Moreover, an outstanding light utilization efficiency of 3.39% is also obtained with an AVT of 30.0% and a PCE of 11.3% in a translucent device by tuning the electrode. The work demonstrates a new and simple strategy for achieving excellent AVT and PCE in ST-OSCs with simplified device structure.