Organic photovoltaic cells for low light applications offering new scope and orientation

Organic photovoltaic (OPV) cells have attracted significant interest for indoor applications with the arrival of the Internet of Things. However, the studies on the essential fundamental issues are still insufficiency under low light. Thus, the properties of OPV cells for low light applications need further clarification. Here, we systematically studied the effect of series resistance (R-s) on the PBDB-TF:IT-M-based device by introducing external R-s and tuning active layer thickness. Regardless of enlarging external R-s or increasing active layer thickness, the efficiencies were observably improved under low light, compared with the AM 1.5G condition. The phenomenon can be mainly attributed to impressive fill factor (FF) under low light due to the restrained recombination processes. Furthermore, we provided the energy distribution through the optical analysis for the OPV cells. The fabricated OPV cells (4 cm(2)) via the blade-coating method output an outstanding power conversion efficiency (PCE) of 21.2% and 10.5% with optimal thicknesses of 181 +/- 37 nm under weak LED light and 0.5% sun, respectively, which are significantly higher than the value of 5.02% under the AM 1.5G condition. Our work shows that OPV cells have great potential in industrialization for low light applications.