Jiang Kui, Westbrook Robert J E, Xia Tian, Zhong Cheng, Lu Jianxun, Khasbaatar Azzaya, Liu Kaikai, Lin Francis R, Jang Sei-Hum, Zhang Jie, Li Yuqing, Diao Ying, Wei Zhanhua, Yip Hin-Lap, Ginger David S, Jen Alex K-Y
Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong.
Department of Chemistry, University of Washington, Seattle, WA, USA.
Nat Commun. 2025 Apr 3;16(1):3176. doi: 10.1038/s41467-025-58352-x.
Efficient delocalization of photo-generated excitons is a key to improving the charge-separation efficiencies in state-of-the-art organic photovoltaic (OPV) absorber. While the delocalization in non-fullerene acceptors has been widely studied, we expand the scope by studying the properties of the conjugated polymer donor D18 on both the material and device levels. Combining optical spectroscopy, X-ray diffraction, and simulation, we show that D18 exhibits stronger π-π interactions and interchain packing compared to classic donor polymers, as well as higher external photoluminescence quantum efficiency (~26%). Using picosecond transient absorption spectroscopy and streak camera photoluminescence measurements, we show that the initial D18 excitons form delocalized intermediates, which decay radiatively with high efficiency in neat films. In single-component OPV cells based on D18, these intermediate excitations can be harvested with an internal quantum efficiency >30%, while in blends with acceptor Y6 they provide a pathway to free charge generation that partially bypasses performance-limiting charge-transfer states at the D18:Y6 interface. Our study demonstrates that donor polymers can be further optimized using similar design strategies that have been successful for non-fullerene acceptors, opening the door to even higher OPV efficiencies.
光生激子的有效离域是提高现有有机光伏（OPV）吸收体中电荷分离效率的关键。虽然非富勒烯受体中的离域已得到广泛研究，但我们通过在材料和器件层面研究共轭聚合物供体D18的性质来扩大研究范围。结合光谱学、X射线衍射和模拟，我们表明，与经典供体聚合物相比，D18表现出更强的π-π相互作用和链间堆积，以及更高的外部光致发光量子效率（约26%）。使用皮秒瞬态吸收光谱和条纹相机光致发光测量，我们表明初始的D18激子形成离域中间体，其在纯薄膜中高效地辐射衰减。在基于D18的单组分OPV电池中，这些中间激发可以以大于30%的内量子效率被捕获，而在与受体Y6的共混物中，它们提供了一条自由电荷产生的途径，部分绕过了D18:Y6界面处限制性能的电荷转移态。我们的研究表明，可以使用对非富勒烯受体成功的类似设计策略进一步优化供体聚合物，为实现更高的OPV效率打开了大门。
