Study of the Cu(In,Ga)Se₂ crystallization process through a combination of <i>in-situ</i> characterization techniques

Abstract This study investigates the crystallization process of amorphous Cu(In,Ga)Se 2 (CIGSe) through in-situ characterization techniques, specifically Raman spectroscopy, x-ray diffraction (XRD), and transmission electron microscopy (TEM). Amorphous CIGSe was deposited through sputtering of a ternary target with simultaneous supply of selenium by evaporation. A Se capping layer revealed to enhance crystallization at lower temperatures, yielding larger crystallites at 400 °C and larger crystal grains after the crystallization process. The A 1 Raman mode of CIGSe appears at a lower temperature and with higher intensity in samples with Se capping compared to those without capping layer. The effect of temperature on the Raman spectra was considered by fitting post-crystallization data with a three-phonon coupling model, allowing for deconvolution of the thermal and material crystallization effects. In-situ XRD data corroborate the Raman data and revealed the formation of MoSe 2 and Cu 2 Se secondary phases at 250 °C and 400 °C, respectively. Moreover, in-situ TEM allowed to further assess crystal growth during the crystallization process.