Enabling High Efficiency, Flexible, and Lightweight CdTe Solar Cells with a Cadmium Stannate Transparent Conducting Oxide

Fabrication of high-efficiency solar cells using a light weight, flexible substrate has been a challenge due to the high-temperature device fabrication processes. One substrate that can withstand the process temperatures is Corning (R) Willow (R) glass; however, this material does not include a transparent conduction oxide (TCO), which is critical to high performance CdTe-based solar cells typically fabricated in the superstrate configuration. Here, we investigate the properties of cadmium stannate (CTO) as a TCO layer for CdTe solar cells. To improve the transmission, conductivity, and crystallinity of the as-deposited CTO layer, the Willow (R)/CTO films were put in contact with a CdS/substrate film and annealed at 600 degrees C under high vacuum condition. After this proximity anneal, the device was fabricated by depositing an indium gallium oxide (IGO) emitter, CdSe, and CdTe, followed by device processing. The efficiency of the devices improved to 16.1% with a specific power density of similar to 700 W/kg compared to devices in which the CTO did not undergo the proximity anneal have efficiency of 12.5%. These results CTO is a promising TCO for fabricating high efficiency, lightweight, flexible CdTe solar cells which could be applicable to space applications.