Li Jiacong, Ji Qing, Wang Rui, Zhang Zhi-Guo, Wang Xiaoyong, Xiao Min, Lu Yan-Qing, Zhang Chunfeng
National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, China.
College of Physics, Nanjing University of Aeronautics and Astronautics, and Key Laboratory of Aerospace Information Materials and Physics (NUAA), MIIT, Nanjing 211106, China.
J Am Chem Soc. 2024 Jul 24;146(29):20312-20322. doi: 10.1021/jacs.4c05786. Epub 2024 Jul 9.
Organic photovoltaic (OPV) devices attain high performance with nonfullerene acceptors by utilizing the synergistic dual channels of charge generation that originate from excitations in both the donor and acceptor materials. However, the specific intermediate states that facilitate both channels are subject to debate. To address this issue, we employ time-resolved terahertz spectroscopy with improved sensitivity (Δ/ < 10), enabling direct probing of charge generation dynamics in a prototypical PM6:Y6 bulk heterojunction system under one-sun-equivalent excitation density. Charge generation arising from donor excitations is characterized with a rise time of ∼9 ps, while that from acceptor excitations shows a rise time of ∼18 ps. Temperature-dependent measurements further reveal notably distinct activation energies for these two charge generation pathways. Additionally, the two channels of charge generation can be substantially manipulated by altering the ratio of bulk to interfaces. These findings strongly suggest the presence of two distinct intermediate states: interfacial and intramoiety excitations. These states are crucial in mediating the transfer of electrons and holes, driving charge generation within OPV devices.
有机光伏（OPV）器件通过利用源自供体和受体材料中激发的电荷产生协同双通道，使用非富勒烯受体实现了高性能。然而，促进这两个通道的特定中间态仍存在争议。为了解决这个问题，我们采用了具有更高灵敏度（Δ/ < 10）的时间分辨太赫兹光谱，能够在等效于一个太阳的激发密度下直接探测典型的PM6:Y6体异质结系统中的电荷产生动力学。供体激发产生的电荷产生的上升时间约为9皮秒，而受体激发产生的电荷产生的上升时间约为18皮秒。温度相关测量进一步揭示了这两种电荷产生途径具有明显不同的活化能。此外，通过改变体相与界面的比例，可以显著调控电荷产生的两个通道。这些发现有力地表明存在两种不同的中间态：界面激发和部分内激发。这些态对于介导电子和空穴的转移、推动OPV器件中的电荷产生至关重要。
