Nanoscale Balance\nof Energy Loss and Quantum Efficiency\nfor High-Efficiency Polythiophene-Based Organic Solar Cells

Polythiophene donors offer scalable and cost-effective\nsolutions\nfor the organic photovoltaic industry. A thorough understanding of\nthe structure–property–performance relationship is essential\nfor advancing polythiophene-based organic solar cells (PTOSCs) with\nhigh power conversion efficiencies (PCEs). Herein, we develop two\npolythiophene donorsPTTz-CN and PTTz-CN(T2)to verify\nthe energy loss–quantum efficiency relationship. The strong\npreaggregation property of PTTz-CN improves quantum efficiency in spite of high nonradiative\nrecombination energy loss, while PTTz-CN(T2) chains are weakly preaggregated,\ncausing low quantum efficiency, accompanied by low nonradiative recombination\nenergy loss though. Synergistically optimized energy loss and quantum\nefficiency are achieved by judiciously mixing PTTz-CN and PTTz-CN(T2),\ndelivering outstanding PCEs of up to 16.4% in the PTOSC system and\n19.6% in an archetype of a high-performing OSC containing the optimal\nPTTz-CN:PTTz-CN(T2) composition. We highlight the significance of\na desirable balance between energy loss and quantum efficiency via\nmolecular interaction tuning of polythiophene donors to improve the\nPTOSC performances.