Acta Phys. -Chim. Sin. ›› 2016, Vol. 32 ›› Issue (8): 1967-1976.doi: 10.3866/PKU.WHXB201604292

• ARTICLE • Previous Articles     Next Articles

Quasiparticle Band Structures and Optical Properties of Graphitic Carbon Nitrides

Dong-Mei LIANG1,2,Xia LENG1,Yu-Chen MA1,*()   

  1. 1 School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, P. R. China
    2 College of Physics and Electronic Engineering, Kaili University, KaiLi 556011, Guizhou Province, P. R. China
  • Received:2016-03-02 Published:2016-07-29
  • Contact: Yu-Chen MA E-mail:myc@sdu.edu.cn
  • Supported by:
    The project was supported by the National Natural Science Foundation of China(21173130);The project was supported by the National Natural Science Foundation of China(21433006);The project was supported by the National Natural Science Foundation of China(21573131)

Abstract:

The excited-state properties of two-dimensional carbon nitrides, including triazine and tri-s-triazine, were investigated using many-body Green's function theory. Their quasiparticle energies were calculated with the GW method. By solving the Bethe-Salpeter equation (BSE), which takes into account electron-hole interactions, excitation energies and optical spectra were obtained. Strong interactions, mainly originating from exchange interactions, were found between σ and π orbitals in the valence bands of the two carbon nitrides. The quasiparticle corrections for occupied σ and π orbitals are quite different, so both of them need to be calculated at the level of the GWmethod to obtain accurate results for both band gaps and optical spectra from the BSE. Compared with monolayer carbon nitrides, interlayer van der Waals interactions in bilayer systems lower the band gap by 0.6 eV, while the optical absorption spectrum red shifts by 0.2 eV. This is because of the smaller exciton binding energy in bilayer systems. Our calculated positions of the absorption peaks are in good agreement with experiments. The absorption peaks in experiments are dominated by transitions from deep π orbitals to π* orbitals. Coupling between ππ* and σπ* transitions can lead to a weak absorption tail in the long wavelength region. If we tune the polarization direction of the incident light, new strong absorption peaks originating from σπ* transitions emerge at lower energies.

Key words: Graphitic carbon nitride, Quasiparticle band structure, Optical spectrum, Transition, Many-body Green's function theory

MSC2000: 

  • O649