CdTe Solar Cell with Industrial Al:ZnO on Soda-Lime Glass

One avenue to enhance CdTe cell performance is to improve the optical transmission of the transparent conductive oxide (TCO)/window layer stack. In this paper, we examine soda-lime float glass coated with an Al-doped ZnO layer and a buffer layer. The possible advantages of using a ZnO-based TCO include reduced surface roughness, improved transparency, and an integrated buffer layer that can be optimized for use in a CdTe PV device. Device processing was modified to address the chemical and thermal differences between the ZnO-based TCO stack produced by Saint-Gobain and the TCOs previously used at the National Renewable Energy Laboratory (NREL). These process modifications produced ∼ 8% efficiency for devices without a buffer layer. Incorporation of buffer layers has already produced devices with ∼ 11% and > 12% efficiency for CdTe deposition temperatures of 570° and 500°C, respectively.