In-depth resolved Raman scattering analysis for the identification of secondary phases: Characterization of Cu2ZnSnS4 layers for solar cell applications

Abstract

This work reports the in-depth resolved Raman scattering analysis with different excitation wavelengths of Cu2ZnSnS4 layers. Secondary phases constitute a central problem in this material, particularly since they cannot be distinguished by x-ray diffraction. Raman spectra measured with 325 nm excitation light after sputtering the layers to different depths show peaks that are not detectable by excitation in the visible. These are identified with Cu3SnS4 modes at the surface region while spectra measured close to the back region show peaks from ZnS and MoS2. Observation of ZnS is enhanced by resonant excitation conditions achieved when working with UV excitation.

Crystal growth of Cu2ZnSnS4 solar cell absorber by chemical vapor transport with I2

“…Neutron diffraction and Raman spectroscopy analyses would be required in order to ascertain if the crystals obtained under different pressure conditions have significant structural differences. These two techniques are crucial, due to the great complexity of the phase identification for the Cu-Zn-Sn-S system solely by XRD [41,43,53,54].…”

Determination of secondary phases in kesterite Cu2ZnSnS4 thin films by x-ray absorption near edge structure analysis

“…Secondary phases (ZnS, ZnSe, Cu 3 SnS 4 ) have been identified by Raman spectroscopy. 12,13 However, this method suffers from the different absorption coefficients related to the primary and secondary phases making a quantitative analysis very difficult, and we are not aware of a report of a quantitative determination of secondary phases in CZTS by Raman spectroscopy. As will be shown, x-ray absorption spectroscopy (XAS) allows to identify the most important secondary phases and in particular enables the quantification of the ZnS content in CZTS thin film absorber layers.…”

Multiwavelength excitation Raman scattering study of polycrystalline kesterite Cu2ZnSnS4 thin films

“…[5][6][7][8] Raman spectroscopy is one of the most powerful tools for determining the crystalline structure and quality of semiconductor thin films, since the shape and position of Raman peaks are strongly influenced by the presence of defects in the material, either in the form of structural inhomogeneities or secondary phases. [9][10][11][12] In order to achieve better device performance in solar cells based on CZTS absorbers and to improve the usage of Raman spectroscopy as a control method for assessment of crystalline quality and identification of secondary phases in these promising emerging compound semiconductors, it is necessary to obtain better knowledge of their vibrational properties. Theoretical calculations on band structure, optical properties, and intrinsic defects have recently been reported.…”