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

Reducing energy loss (Eloss) is of critical importance to improving the photovoltaic performance of organic solar cells (OSCs). Although nonradiative recombination (Elossnonrad) is investigated in quite a few works, the method for modulating Elossnonrad is seldom reported. Here, a new method of depressing Eloss 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 PBDB‐T:IT‐4F‐based OSC, resulting in lower Elossrad and Elossnonrad, and hence a significant improvement in the open‐circuit voltage (VOC); 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 Eloss for nonfullerene OSCs. [ABSTRACT FROM AUTHOR]