Li Shuang-Bao, Geng Yun, Duan Yu-Ai, Sun Guang-Yan, Zhang Min, Qiu Yong-Qing, Su Zhong-Min
Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People's Republic of China.
Department of Chemistry, Capital Normal University, Beijing 100048, People's Republic of China.
J Chem Phys. 2016 Dec 28;145(24):244705. doi: 10.1063/1.4972005.
A combined molecular dynamics (MD) and quantum chemical (QC) simulation method is utilized to investigate charge generation mechanism at TTF/TCNQ (tetrathiafulvalene/tetracyanoquinodimethane) heterojunction, which is a controversial donor/acceptor (D/A) interface for organic photovoltaic (OPV) devices. The TTF/TCNQ complexes extracted from MD simulation are classified into parallel and herringbone packings. And then, the amounts of charge transferred from ground states to different excited states and the corresponding energies of charge transfer (CT) state are compared and analyzed using QC simulation. Moreover, the electron transfer/recombination rates for these interfacial configurations are also studied. From these data, we have elucidated the underlying reason why TTF/TCNQ heterojunction is inadaptable to OPV application. One main reason is that large |ΔG| (the absolute value of Gibbs free energy change of CT) forms a large energy barrier, limiting exciton dissociation at the TTF/TCNQ heterojunction, and small |ΔG| (the absolute value of Gibbs free energy change of charge recombination) performs the easy recombination to the ground state.
采用分子动力学（MD）和量子化学（QC）相结合的模拟方法，研究了TTF/TCNQ（四硫富瓦烯/四氰基对苯二醌二甲烷）异质结处的电荷产生机制，该异质结是有机光伏（OPV）器件中一个存在争议的供体/受体（D/A）界面。从MD模拟中提取的TTF/TCNQ复合物分为平行堆积和人字形堆积。然后，使用QC模拟比较并分析了从基态转移到不同激发态的电荷量以及相应的电荷转移（CT）态能量。此外，还研究了这些界面构型的电子转移/复合速率。通过这些数据，我们阐明了TTF/TCNQ异质结不适用于OPV应用的根本原因。一个主要原因是大的|ΔG|（CT的吉布斯自由能变化的绝对值）形成了一个大的能垒，限制了TTF/TCNQ异质结处的激子解离，而小的|ΔG|（电荷复合的吉布斯自由能变化的绝对值）则使得容易复合到基态。
