Modulating Aggregation Behavior by Ternary Strategies for Efficient and Stable Thick‐Film Organic Solar Cells

Abstract Functional third components targeted to improve a specific property of organic solar cells is an effective strategy. However, introducing a third component to simultaneously improve efficiency and stability and achieve good performance in thick‐film devices has rarely been reported. Herein, low diffusion third components IDCN and ID2CN are reported to achieve a power conversion efficiency (PCE) of 18.08% and a high short‐circuit current ( J _SC ) of 27.82 mA cm ⁻² , one of the highest values based on PM6:Y6. They increase light harvesting in the range of 400–500 nm while enhancing energy transfer via Förster resonance energy transfer (FRET). A tightly ordered molecular arrangement is achieved by modulating the preaggregation and film formation kinetics of Y6, which enhance exciton dissociation and charge transport. Moreover, the low‐diffusion third component can effectively restrict the diffusion of Y6 to improve the morphology stability, and the T ₉₀ lifetime is increased from 689 to 1545 h. In 300 nm thick‐film devices, PM6:ID2CN:Y6 achieves a PCE of 15.01%, much higher than PM6:Y6's 12.83%, demonstrating the great potential of ID2CN in thick‐film devices.