An Electron Paramagnetic Resonance and Photoelectron Spectroscopy Study on the Native Oxidation of CuGaSe2

Abstract

AbstractThe complementary techniques of electron paramagnetic resonance (EPR) and photoelectron spectroscopy (PES) have been used to study the native oxidation of CuGaSe2 crystals and polycrystalline thin films. After storage of specimen under ambient conditions for few months, an EPR signal occurred which is assigned to Cu2+ and is found independently from the sample morphology. This signal is due to the formation of a copper hydroxide surface phase, Cu(OH)2, observed only after long term oxidation. Chemical etching in KCN removes and thermal reduction by annealing in vacuum at 200°C reduces this Cu(OH)2 surface phase as proved by EPR and PES. Implications for solar cell device performance will be discussed.