The charge-transfer states and excitation energy transfers of halogen-free organic molecules from first-principles many-body Green's function theory

Yaoyao Wei; Yunzhi Li; Guangli Zhou; Guokui Liu; Xia Leng; Qiying Xia

doi:10.1016/j.saa.2022.121925

The charge-transfer states and excitation energy transfers of halogen-free organic molecules from first-principles many-body Green's function theory

Spectrochim Acta A Mol Biomol Spectrosc. 2023 Feb 5:286:121925. doi: 10.1016/j.saa.2022.121925. Epub 2022 Sep 27.

Authors

Yaoyao Wei¹, Yunzhi Li¹, Guangli Zhou¹, Guokui Liu¹, Xia Leng², Qiying Xia³

Affiliations

¹ School of Chemistry and Chemical Engineering, Linyi University, Linyi 276000, China.
² School of Chemistry and Chemical Engineering, Linyi University, Linyi 276000, China. Electronic address: lengxia@lyu.edu.cn.
³ School of Chemistry and Chemical Engineering, Linyi University, Linyi 276000, China. Electronic address: xiaqiying@lyu.edu.cn.

PMID: 36244154
DOI: 10.1016/j.saa.2022.121925

Abstract

The organic solar cells based on halogen-free components, have been the new favorites to develop green and renewable energy. PBDB-T and its derivatives are considered the superior electron donors to construct the solar cells. Although there are plenty of researches about them, the charge-transfer mechanisms and excitation energy transfers of relative organic solar cells are still unclear, the developments of photovoltaic devices are restricted consequently. In this work, we calculate the electronic structures and excited-state properties of PBDB-T, PBT1-C, PBT1-O and PBT1-S donors in the gas phase from the many-body Green's function theory. With BTP-IC and BTP-IS as the acceptors, we consider the Förster, Dexter, and overlap electronic couplings to compute the excitation energy transfers of the dimers. The ionization energies and excited-state energies of the four donors calculated by GW + BSE are in good agreement with experiments, and they are sensitive to the functionals in the computation. We find two charge transfer schemes. The thienyl of PBDB-T molecule makes its charge-transfer state at the lowest energy, and the total electronic coupling of PBDB-T based dimer is the strongest. The Dexter, and overlap types electronic couplings are significant to study the excitation energy transfer of organic heterojunctions. We provide a theoretical guide in the design and synthesis of higher-performance halogen-free donors.

Keywords: Electronic energy transfer; Halogen-free; Organic solar cell; PBDB-T.