Molecular beam deposition and characterization of wide-band-gap Cu(In,Ga)se2 for thin film solar cells

Abstract

Mo/ Cu(In, Ga)Se₂/CdS/ZnO thin film solar cells were fabricated and studied on their current transport mechanism. The current-voltage characteristics were measured in the dark and illuminated, at room temperature as well as variety of temperature. The dark and illuminated I-V characteristics were deduced for their diode ideality factor (A), series resistace (R₂) and the reverse saturation current density (Jo) which are related to current transport mechanism through the junction. The I-V characteristic curves at room temperature indicate that current transport process is controlled by the Shockley-Read-Hall (SRH) recombination in the space charge region. The analysis of temperature dependent current-voltage I(V,T) measurement indicates that the tunneling contributes to the recombination in the space charge region at low temperature. The studies of the effect of impurity concentration in the CdS buffer layer and the effect of illumination intensity on the I-V characteristics were analyzed and used to draw a possible energy band diagram of the device. It is also used to explain the current transport mechanism at junction.