Light-induced metastabilities in the interface region of Cu(In,Ga)Se2-based photovoltaic devices studied by Laplace transform junction spectroscopy

The combined method of Reverse-bias Deep Level Transient Spectroscopy (RDLTS) and inverse Laplace transform analysis provide a tool for investigation of interface states of superior spectral resolution compared to other junction techniques. It has been applied for studying response from interface states in ZnO/CdS/Cu(In,Ga)Se-2 thin film photovoltaic devices. The metastable enhancement of emission rates from interface due to illumination has been investigated. The results put in question former interpretation of junction-spectroscopic results based on the model of interface states equilibrating with the bands and suggest trap-assisted tunneling as a main path of carrier transport to interface states. Metastability of the interface response has been interpreted as due to the persisting increase of the tunneling probability.