Correlation of stability to varied CdCl2 treatment and related defects in CdS/CdTe PV devices as measured by thermal admittance spectroscopy

A correlation between the CdCl2 treatment and the change in conversion efficiency with light and heat stress indoors (stability) has been shown previously by our group for CdS/CdTe:Cu PV devices. In the present work CdTe devices were fabricated with various CdCl2 treatments and with and without a Cu containing back contact. The electrical characteristics of the defects acting as traps in these devices were studied using thermal admittance spectroscopy (TAS). The activation energy Et−EV, the apparent capture cross section and the densities of state functions (using Walter's method) of the traps in the devices were estimated.