Zhu Lingyun, Zhang Jianqi, Guo Yuan, Yang Chen, Yi Yuanping, Wei Zhixiang
CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China.
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
Angew Chem Int Ed Engl. 2021 Jul 5;60(28):15348-15353. doi: 10.1002/anie.202105156. Epub 2021 Jun 8.
Organic solar cells (OSCs) with nonfullerene acceptors (NFAs) exhibit efficient charge generation under small interfacial energy offsets, leading to over 18 % efficiency for the single-junction devices based on the state-of-the-art NFA of Y6. Herein, to reveal the underlying charge generation mechanisms, we have investigated the exciton binding energy (E ) in Y6 by a joint theoretical and experimental study. The results show that owing to strong charge polarization effects, Y6 has remarkable small E of -0.11-0.15 eV, which is even lower than perovskites in many cases. Moreover, it is peculiar that the photoluminescence is enhanced with temperature, and the energy barrier for separating excitons into charges is evidently lower than the thermal energy according to the temperature dependence of photoluminescence, manifesting direct photogeneration of charge carriers enabled by weak E in Y6. Thus, charge generation in NFA-based OSCs shows little dependence on interfacial driving forces.
具有非富勒烯受体（NFAs）的有机太阳能电池（OSCs）在小界面能差下表现出高效的电荷产生，基于Y6这种最先进的NFA的单结器件效率超过18%。在此，为了揭示潜在的电荷产生机制，我们通过理论与实验联合研究对Y6中的激子结合能（E）进行了研究。结果表明，由于强烈的电荷极化效应，Y6具有显著小的E，为-0.11 - 0.15 eV，在许多情况下甚至低于钙钛矿。此外，奇特的是光致发光随温度增强，并且根据光致发光的温度依赖性，将激子分离为电荷的能量势垒明显低于热能，这表明Y6中弱的E使得电荷载流子能够直接光生。因此，基于NFA的OSCs中的电荷产生对界面驱动力的依赖性很小。
