Raman investigations of Cu(In,Ga)Se2 thin films with various copper contents

Abstract CuIn1 − xGaxSe2 (CIGS) thin films with a Ga/(Ga + In) ratio x = 0.3 with various Cu contents were characterized by micro-Raman spectroscopy. All samples were investigated with a frequency-doubled Nd:YAG laser (532 nm) in the back-scattering geometry. The frequency of the CIGS Raman A1 mode decreases with increasing Cu content and reaches a minimum at a composition near stoichiometry. Furthermore, the full width at half maximum of the A1 mode decreases with increasing Cu content of the CIGS thin films due to better crystallinity and reduced disorder in the films. In addition to the CIGS A1 mode, CIGS with Cu/(Ga + In) 1 exhibit a non-chalcopyrite mode at 260 cm− 1 which is assigned to Cu2 − xSe. Mappings of Cu-rich samples revealed a lateral distribution of the Cu2 − xSe compound in domains of 1–2 μm.