南京大学张春峰研究团队利用高灵敏度太赫兹光谱，检测单太阳等效光照下有机光伏共混物的电荷生成动力学。相关研究成果于2024年7月9日发表在国际顶尖学术期刊《美国化学会志》。

有机光伏(OPV)器件通过利用来自供体和受体材料激发的电荷产生的协同双通道，获得了非富勒烯受体的高性能。然而，促进这两种通道的具体中间状态仍有待商榷。

为了解决这个问题，研究人员使用了灵敏度提高的时间分辨太赫兹光谱（ΔE/E<10^–6），从而能够在一个标准阳光等效激发密度下，直接探测原型PM6:Y6体异质结系统中的电荷生成动力学。由施主激发产生的电荷的上升时间为～9ps，而由受主激发产生的则为～18ps。与温度相关的测量进一步揭示了这两种电荷产生途径明显不同的活化能。此外，可以通过改变体与界面的比率来基本上操纵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：界面激发和物质内激发。这些状态在介导电子和空穴的转移、驱动OPV器件内的电荷产生方面至关重要。

附：英文原文

Title: Charge Generation Dynamics in Organic Photovoltaic Blends under One-Sun-Equivalent Illumination Detected by Highly Sensitive Terahertz Spectroscopy

Author: Jiacong Li, Qing Ji, Rui Wang, Zhi-Guo Zhang, Xiaoyong Wang, Min Xiao, Yan-qing Lu, Chunfeng Zhang

Issue&Volume: July 9, 2024

Abstract: 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 (ΔE/E < 10–6), 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.

DOI: 10.1021/jacs.4c05786

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c05786