<p>Balancing the high photocurrent production and the nonradiative recombination suppression is of practical importance to design high-performance organic bulk heterojunction (BHJ) solar cells. Most efforts in this field have been directed towards the understanding of the electronic charge and photogenerated exciton related optoelectronic and transient processes. Little is known about the spin polaron pairs (PPs) dependent dissociation and nonradiative decay at charge transfer states (CTS), where the coherent spin mixing plays a key role. In this work, we combine magneto-photocurrent (MPC) and coherent spin mixing analyses for the IT- and Y-series, i.e., prototypical nonfullerene acceptors (NFA), based organic BHJ systems. We find that increasing polaron pair dissociation rates at singlet charge transfer states (CTS)^S give rise to the photocurrent generation. Within the same systems, strong internal fields that include the hyperfine (HF) fields, spin-orbit coupling (SOC), and Δ<i>g</i> value may promote the intersystem crossing (ISC) and the polaron back transfer (PBT), leading to the energy loss. By exploring the impact of the coherent spin mixing on the molecular functionality, our study opens new directions for improving photovoltaic performance of BHJ systems.</p>