Isogenous Acceptor Strategy Enables Highly Efficient Ternary Organic Solar Cells via Synergistic Morphology Regulation and Charge Recombination Reduction

Isogenous acceptor strategy is considered to be able to effectively improve the power conversion efficiency (PCE) of ternary organic solar cells (OSCs) by maximizing the absorption and optimizing the morphologies of active layers. Herein, a Y6-like small-molecular non-fullerene acceptor of m-BTP-PhC6 is employed as the second acceptor to tune the photovoltaic performance of D18-CI: Y6:m-BTP-PhC6-based ternary OSCs. A highest PCE up to 18.03% is achieved with an optimized Y6:m-BTP-PhC6 blend ratio of 4:1, with a V-OC of 0.871 V, a/(SC) of 26.80 mA cm(-2) , and a FF of 77.32%, respectively. Compared to D18-CI:Y6 binary system, it was found that the introduction of m-BTP-PhC6 expanded the spectral absorption range and provided a good cascade energy level matching. The light intensity dependence results demonstrate that ternary blending could significantly promote the photogenerated charge dissociation and transporting, meanwhile suppressing the bimolecular recombination. Transient absorption (TA) results further depicted a decay lifetime of 0.84 ps of D18-CI:Y6 binary in contrast to 0.69 ps of the D18-CI:Y6:m-BTP-PhC6 ternary film, indicating a faster hole transfer dynamic. The work presents a promising isogenous acceptor strategy to improve the efficiency of ternary OSCs.

Automated summary

The isogenous acceptor strategy is shown to effectively enhance the efficiency of ternary organic solar cells. By introducing m-BTP-PhC6 as the second acceptor, the absorption range is expanded and the energy level alignment is optimized, resulting in improved photovoltaic performance.