Effects of Na incorporated at different periods of deposition on Cu(In,Ga)Se_2 films

Abstract

Sodium was incorporated into Cu(In,Ga)Se(2) (CIGS) thin films by evaporating NaF before the second and third stages and after the third stage of CIGS deposition. The Na-doping dosage was precisely controlled by a light-controlling method based on reflected light signals. X-ray diffraction and scanning electron microscopy results reveal that CIGS crystalline growth and microstructure can be strongly influenced by periods of Na incorporation, which leads to different device performance characteristics. Based on the analysis of results, incorporating Na before the second stage of the standard three-stage process is suggested.