Reduced Nonradiative Energy Loss Caused by Aggregation of Nonfullerene Acceptor in Organic Solar Cells

Reducing energy loss (E-loss) is of critical importance to improving the photovoltaic performance of organic solar cells (OSCs). Although nonradiative recombination (E-loss(nonrad)) is investigated in quite a few works, the method for modulating E-loss(nonrad) is seldom reported. Here, a new method of depressing E-loss is reported for nonfullerene OSCs. In addition to ternary-blend bulk heterojunction (BHJ) solar cells, it is proved that a small molecular material (NRM-1) can be selectively dispersed into the acceptor phase in the PBDBT:IT-4F-based OSC, resulting in lower E-loss(rad) and E-loss(nonrad), and hence a significant improvement in the open-circuit voltage (V-OC); under an optimal feed ratio of NRM-1, an enhanced power conversion efficiency can also be gained. Moreover, the role of NRM-1 in the method is illustrated and its applicability for several other representative OSCs is validated. This work paves a new pathway to reduce the E-loss for nonfullerene OSCs.