Nanoscale Balance of Energy Loss and Quantum Efficiency for High-Efficiency Polythiophene-Based Organic Solar Cells

Polythiophene donors offer scalable and cost-effective solutions for the organic photovoltaic industry. A thorough understanding of the structure–property–performance relationship is essential for advancing polythiophene-based organic solar cells (PTOSCs) with high power conversion efficiencies (PCEs). Herein, we develop two polythiophene donors─PTTz-CN and PTTz-CN(T2)─to verify the energy loss–quantum efficiency relationship. The strong preaggregation property of PTTz-CN improves quantum efficiency in spite of high nonradiative recombination energy loss, while PTTz-CN(T2) chains are weakly preaggregated, causing low quantum efficiency, accompanied by low nonradiative recombination energy loss though. Synergistically optimized energy loss and quantum efficiency are achieved by judiciously mixing PTTz-CN and PTTz-CN(T2), delivering outstanding PCEs of up to 16.4% in the PTOSC system and 19.6% in an archetype of a high-performing OSC containing the optimal PTTz-CN:PTTz-CN(T2) composition. We highlight the significance of a desirable balance between energy loss and quantum efficiency via molecular interaction tuning of polythiophene donors to improve the PTOSC performances.