Influence of secondary phase CuxSe on the optoelectronic quality of chalcopyrite thin films

Abstract

The effect of secondary phase CuxSe on the absorber quality of epitaxial CuGaSe2 films is studied by spatially resolved photoluminescence combined with scanning electron microscopy. We show that the presence of CuxSe crystals on the absorber during growth under Cu excess results in a locally increased crystal quality in the vicinity of the CuxSe crystallites, affecting the defect structure of the absorber. This effect remains after removal of CuxSe and induces a local reduction in the recombination centers, resulting in locally higher excess carrier concentrations and larger splitting of quasi-Fermi levels.