Ternary strategy is one of the most effective methods to further boost the power conversion efficiency (PCE) of organic photovoltaic cells (OPVs). In terms of high-efficiency PM6:Y6 binary systems, there is still room to further reduce energy loss (E_loss) through regulating molecular packing and aggregation by introducing a third component in the construction of ternary OPVs. Here we introduce a simple molecule BR1 based on an acceptor-donor-acceptor (A-D-A) structure with a wide bandgap and high crystallinity into PM6:Y6-based OPVs. It is proved that BR1 can be selectively dispersed into the donor phase in the PM6:Y6 and reduce disorder in the ternary blends, thus resulting in lower E_{loss, non-rad} and E_loss. Furthermore, the mechanism study reveals well-develop phase separation morphology and complemented absorption spectra in the ternary blends, leading to higher charge mobility, suppressed recombination, which concurrently contributes to the significantly improved PCE of 17.23% for the ternary system compared with the binary ones (16.21%). This work provides an effective approach to improve the performance of the PM6:Y6-based OPVs by adopting a ternary strategy with a simple molecule as the third component.