The Stability and Performance of Amorphous-InZnO within CIGS Devices

NREL CIGS devices with up to 20% efficiency are prepared using a three-stage process for the CIGS layer with the last step of an intrinsic ZnO and conductive ZnO:Al bilayer. This work outlines the efficiency and performance parameters for these CIGs devices when this bilayer is replaced with indium zinc oxide (a-InZnO), an amorphous metal oxide. It is well known that metal oxides can serve a variety of important functions in thin film photovoltaics such as transparent electrical contacts (TCO's), antireflection coatings and chemical barriers. In the case of a-InZnO, we have reported on the determination of the relative roles of metals and oxygen stoichiometries on the opto-electronic properties of a-InZnO thin films as well as the stability of those films in damp heat. Since InZO has a tunable conductivity based on the amount of oxygen introduced during deposition, it can be used as both the intrinsic and TCO layers. We were able to establish preliminary metrics for an all InZnO bilayer whose performance was comparable to a common CIGs device.