非富勒烯有机体异质结中磁光电流及相干自旋混合理论研究进展

Research Progresses on Magneto-photocurrent and Coherent Spin Mixing Theory in Nonfullerene Organic Bulk Heterojunctions

有机非富勒烯分子受体,又称稠环电子受体,由于其优良的光电转换性质,现已成为备受关注的有机光电子材料之一。基于该类材料所发展的有机体异质结太阳能电池,其能量转换效率已逼近20%。而制备高效稳定的有机体异质结太阳能电池离不开对材料物性和光伏过程的深入探索。在众多研究体系中,非富勒烯光伏自旋动力学的发展尚处于起步阶段,其内在的光物理机理尚未明确。而光激发磁光电流技术能通过监测有机体异质结中极化子对的解离,在器件工作状态下,原位表征光伏自旋动力学过程。本文结合实验和理论研究,科学地阐述目前主流的有机磁光电流理论基础及函数模型,如低磁场下的超精细耦合效应和自旋-轨道耦合效应,高磁场下的Δg机制;探讨不同有机体异质结在不同表征条件下如偏压、温度、光强的信号差异;最后,讨论了超快光谱技术在有机体异质结体系中的应用。

Organic nonfullerene acceptors,also called fused-ring electron acceptors,are the present one of the mostly attractive organic optoelectronic materials due to their prominent photoelectric conversion property.Based on these materials for the development of organic bulk heterojunction solar cells,their power conversion efficiencies have approached 20%already.Fabrications of highly efficient and stable organic photovoltaic devices are insepara‐ble with continuous explorations on material properties and photovoltaic processes.Among many research systems,the growth of the nonfullerene photovoltaic spin dynamics remains in its infant stage,and its underlying physical mechanism is not yet clear.The photoexcited magneto-photocurrent technique can rationally monitor the polaron pair dissociation at charge transfer states,for a device at working conditions,the technique acts as a powerful tool for in-situ characterizations of photovoltaic spin dynamics.This article contains a joint of experimental and theoretical stud‐ies,to scientifically elucidate the present mainstream theories and functional models.These include the hyperfine in‐teraction and the spin-orbit coupling effect at low magnetic fields,and theΔg mechanism at high magnetic fields.The paper explores signal differences in different organic heterojunctions under various characterization conditions,such as bias,temperature and light intensity.Finally,we discuss the applications of the ultrafast spectroscopic tech‐nique in the organic bulk heterojunction systems.