Analysis of EBIC time-variation using 2D simulation including charge states in V _Se–V _Cu divacancy complex

Abstract

Electron beam induced current (EBIC) measurements have been widely used to investigate charge carrier collection in Cu(In,Ga)Se2 (CIGS) solar cells. However, we found that this electron beam irradiation can significantly change the EBIC signal intensity during the measurement. In this study, the charge state variation of the VSe–VCu divacancy proposed by Lany et al. was introduced into the device simulator to explain the phenomenon. In the simulation, the defects take three different charged states, i.e., positive, neutral, and negative states, where their transitions are affected by the quasi-Fermi level position in the bandgap. The transient response of the EBIC signal was successfully explained by incorporating these complex state defects.