Reversible Cu2−xSe↔Cu3Se2 phase transformation in copper selenide thin films prepared by chemical bath deposition

Abstract This paper reports the inter phase conversion of Cu 2− x Se and Cu 3 Se 2 thin films prepared using the chemical bath deposition (CBD) technique. Chemically prepared Cu 2− x Se phase is found to be less stable than the Cu 3 Se 2 phase in ambient conditions. With aging the Cu 2− x Se phase gets converted to the Cu 3 Se 2 phase along with the formation of copper oxide impurity. The Cu 3 Se 2 phase is stable in ambient conditions but is unstable at temperatures above 140°C where it reverts to the Cu 2− x Se phase. This inter phase conversion is found to be cyclic. The relative stability of these phases is studied in detail with the help of X-ray diffraction, optical absorption and X-ray photoelectron spectroscopy.