Lateral inhomogeneities of Cu(In,Ga)Se-2 absorber films

Scanning tunneling microscopy (STM) under laser illumination and microspot X-ray photoelectron spectroscopy (micro-ESCA) have been utilized to study t he 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 cle arly demonstrate that the photovoltaic quantities like the local surface ph otovoltage (SPV) and photoinduced tunneling current (PITC) vary significant ly between different grains. This observation is in accordance with the loc al variation of the chemical composition of CIGS absorber films derived by micro-ESCA. In addition, the (local) photoelectric parameters vary with exp osure time to red light. in agreement with recently reported metastability effects. (C) 2000 Elsevier Science S.A. All rights reserved.