Nonradiative Energy Loss Generated by Two Hidden Trade-Offs in Non-Fullerene Organic Solar Cells with the Positive Correlation between JS']JSC and VOC

Non-fullerene organic solar cells (OSCs) achieve the simultaneous enhancement of short-circuit current density (JSC) and open-circuit voltage (VOC), which will be defined as positive correlation in this work. However, it has not ushered in a breakthrough of power conversion efficiency (PCE). We reveal that the essence lies in two hidden trade-offs, issued from the two-sidedness of electronic coupling (Vel) and thus resulting in the competition between the increasing magnitudes of JSC and VOC. A great Vel could improve the energy of the charge-transfer state, leading to a phenomenon called positive correlation. Nevertheless, it also induces the large nonradiative energy loss and is adverse to the increasing magnitude of JSC or VOC simultaneously, limiting the great improvement in PCE. Overall, we reveal the qualitative change point of trade-offs in non-fullerene OSCs by the quantitative change of microscopic difference under the loss pathway.