Growth process monitoring and crystalline quality assessment of CuInS(Se) 2 based solar cells by Raman spectroscopy

Abstract

This work reviews the use of Raman scattering for the crystalline quality assessment of CuInS(Se) 2 thin film chalcopyrite materials for photovoltaic applications. The Raman spectra of these semiconductors show a dominant A 1 mode with spectral features sensitive to the microcrystalline quality of the layers. The spectra are also characterised by additional modes, which have been interpreted and modelled as related to the existence of polymorphic domains with Cu–Au ordering. This interpretation is supported by the detailed microstructural analysis of various specimens, including epi- and polycrystalline layers obtained under different stoichiometric regimes leading to significant differences in final solar cell efficiency. The relative intensity of these additional modes in the spectra is proposed for the monitoring and quality assessment of the absorber layers for photovoltaic devices. Besides, identification of the main vibrational modes related to secondary phases characteristic of the different thin film growth processes allows the use of the technique for process monitoring. Moreover, thanks to its non-destructive character, its implementation can be in principle designed at both in situ and ex situ levels.