Theoretical study on the charge transfer mechanism at donor/acceptor interface: Why TTF/TCNQ is inadaptable to photovoltaics?

Shuang-Bao Li; Yun Geng; Yu-Ai Duan; Guang-Yan Sun; Min Zhang; Yong-Qing Qiu; Zhong-Min Su

doi:10.1063/1.4972005

Theoretical study on the charge transfer mechanism at donor/acceptor interface: Why TTF/TCNQ is inadaptable to photovoltaics?

J Chem Phys. 2016 Dec 28;145(24):244705. doi: 10.1063/1.4972005.

Authors

Shuang-Bao Li¹, Yun Geng¹, Yu-Ai Duan², Guang-Yan Sun³, Min Zhang¹, Yong-Qing Qiu¹, Zhong-Min Su³

Affiliations

¹ Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People's Republic of China.
² Department of Chemistry, Capital Normal University, Beijing 100048, People's Republic of China.
³ Department of Chemistry, Faculty of Science, Yanbian University, Yanji 133002, People's Republic of China.

PMID: 28049323
DOI: 10.1063/1.4972005

Abstract

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_CT| (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_CR| (the absolute value of Gibbs free energy change of charge recombination) performs the easy recombination to the ground state.