Lateral inhomogeneities of Cu(In,Ga)Se2 absorber films

Abstract Scanning tunneling microscopy (STM) under laser illumination and microspot X-ray photoelectron spectroscopy (micro-ESCA) have been utilized to study the local variation of the photovoltaic properties and of the stoichiometry of Cu(In,Ga)Se 2 (CIGS) thin film solar cell absorbers. The STM results clearly demonstrate that the photovoltaic quantities like the local surface photovoltage (SPV) and photoinduced tunneling current (PITC) vary significantly between different grains. This observation is in accordance with the local variation of the chemical composition of CIGS absorber films derived by micro-ESCA. In addition, the (local) photoelectric parameters vary with exposure time to red light, in agreement with recently reported metastability effects.