Non-Radiative Recombination of Triplet Charge-Transfer State as the Key of Limiting Efficiency Mediates the Positive Relevance of JSC and VOC

Abstract Non-fullerene organic solar cells (NF OSCs) with A-D-A acceptors have realized the positive relevance of short-circuit current density (JSC) and open-circuit voltage (VOC), because of the restricted energy loss. However, non-radiative energy loss remains unclear, resulting in the positive relevance could not maximize power conversion efficiency (PCE). Here, the impact of non-radiative recombination directly related to the singlet- and triplet-charge-transfer (1CT and 3CT) states on the positive relevance is explored. It establishes the essential connection between 3CT-state non-radiation and positive relevance, points out the former mainly hinders PCE. The root reason is that decisive factors of decay rates in two pathways are completely different, but hard to adjust coordinately. Especially, another trade-off is still detected in NF OSCs, causing a bottleneck in PCE. To the end, we propose the defects of A-D-A molecular design by revealing 3CT-state non-radiation mediates the positive relevance.