Spectroscopy and Theoretical Modeling of Phonon Vibration Modes and Band Gap Energy of Cu2ZnSn(S x Se1- x )4 Bulk Crystals and Thin Films

Ivan S Babichuk; Yurii A Romaniuk; Sergii Golovynskyi; Vitali G Hurtavy; Alexander V Mudryi; Vadim D Zhivulko; Iryna V Babichuk; Chengqun Xu; Chubin Lin; Mingxuan Cao; Oleksandr M Hreshchuk; Volodymyr O Yukhymchuk; Mykhailo Ya Valakh; Baikui Li; Jian Yang

doi:10.1021/acsomega.1c04356

Spectroscopy and Theoretical Modeling of Phonon Vibration Modes and Band Gap Energy of Cu₂ZnSn(S _x Se_{1- x} )₄ Bulk Crystals and Thin Films

ACS Omega. 2021 Oct 21;6(43):29137-29148. doi: 10.1021/acsomega.1c04356. eCollection 2021 Nov 2.

Authors

Ivan S Babichuk^{1

2}, Yurii A Romaniuk^{2

3}, Sergii Golovynskyi³, Vitali G Hurtavy⁴, Alexander V Mudryi⁴, Vadim D Zhivulko⁴, Iryna V Babichuk⁵, Chengqun Xu⁶, Chubin Lin¹, Mingxuan Cao¹, Oleksandr M Hreshchuk², Volodymyr O Yukhymchuk², Mykhailo Ya Valakh², Baikui Li³, Jian Yang¹

Affiliations

¹ Faculty of Intelligent Manufacturing, Wuyi University, Jiangmen 529020, P.R. China.
² V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, Kyiv 03680, Ukraine.
³ Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, P.R. China.
⁴ State Research and Production Association "Research and Practice Center for Material Science of the National Academy of Sciences of Belarus", Minsk 220072, Belarus.
⁵ National Center "Minor Academy of Sciences of Ukraine", Kyiv 04119, Ukraine.
⁶ School of Applied Physics and Materials, Wuyi University, Jiangmen 529020, P.R. China.

Abstract

Semiconductor Cu₂ZnSn(S _x Se_1-x )₄ (CZTSSe) solid solution is considered as a perspective absorber material for solar cells. However, during its synthesis or deposition, any modification in the resulting optical properties is hardly predicted. In this study, experimental and theoretical analyses of CZTSSe bulk crystals and thin films are presented based on Raman scattering and absorption spectroscopies together with compositional and morphological characterizations. CZTSSe bulk and thin films are studied upon a change in the x = S/(S + Se) aspect ratio. The morphological study is focused on surface visualization of the solid solutions, depending on x variation. It has been discovered for the first time that the surface of the bulk CZTSSe crystal with x = 0.35 has pyramid-like structures. The information obtained from the elemental analysis helps to consider the formation of a set of possible intrinsic lattice defects, including vacancies, self-interstitials, antisites, and defect complexes. Due to these results and the experimentally obtained values of the band gap within 1.0-1.37 eV, a deviation from the calculated band gap values is estimated in the range of 1.0-1.5 eV. It is suggested which defects can have an influence on such a band gap change. Also, on comparing the experimental Raman spectra of CZTSSe with the theoretical modeling results, an excellent agreement is obtained for the main Raman bands. The proposed theoretical approach allows to estimate the values of concentration of atoms (S or Se) for CZTSSe solid solution directly from the experimental Raman spectra. Thus, the visualization of morphology and the proposed theoretical approach at various x values will help for a deeper understanding of the CZTSSe structure to develop next-generation solar cells.