Suppressing Nonradiative Voltage Losses in Ternary Organic Solar Cells via Additional CT States

Abstract Ternary organic solar cells (TOSCs) have attracted considerable attention due to their high power conversion efficiency (PCE). However, they still suffer from large nonradiative voltage losses ΔVnr, which impede further progress. The fundamental mechanisms responsible for this remain under debate, and the addition of a third component introduces further complexity that warrants deeper theoretical investigation.Here, we construct a model based on a five-state framework incorporating spin-dependent, quantum-evolving states to assess how the third component mitigates ΔVnr. This framework explains previous experiments and provides a theoretical basis with quantitative predictions of energy level to minimize ΔVnr. From our results, we derive two design guidelines for high-performance TOSCs: (i) selecting a third component with good miscibility to ensure tight state coupling; (ii) employing a third component whose relevant energy level lies between the HOMO (or LUMO) of the donor and that of the acceptor.