Controlling the Third Component Distribution Toward High‐Efficient Ternary Organic Solar Cells

Abstract Ternary organic solar cells (T‐OSCs) based on energy transfer can significantly boost the light absorption efficiency, thereby improving their power conversion efficiency (PCE). However, the uncontrolled distribution of the third component in bulk heterojunction (BHJ) device often results in low energy transfer efficiency ( E FRET ), and also tends to compromise the interpenetrating network structure of active layer. Herein, a localized deposition strategy is proposed and establish a bulk heterojunction with a controlled distribution of the third component (CDBHJ). Take PM6:Y6:IBC‐F for example, IBC‐F serves as the energy donor and PM6 as the energy acceptor. Compared with BHJ‐based devices, the proportion of IBC‐F within the PM6 phase increases from 25.1% to 72.7%, enhancing E FRET from 46.5% to 66.8% in CDBHJ‐based devices. Furthermore, the localized deposition strategy improves crystallization and phase separation kinetics during film‐forming process. Thus, the CDBHJ‐based device exhibits superior exciton generation, diffusion, and dissociation process, along with higher and more balanced charge transport. Consequently, the CDBHJ‐based device achieves PCE of 18.29%, which ranks among the best for PM6:Y6‐based T‐OSCs. This work demonstrates the effectiveness of the localized deposition strategy in controlling the distribution of the third component, presenting an innovative pathway for the development of highly efficient T‐OSCs.