By Kari Williamson

Plansee alloys pure molybdenum with small amounts of corrosion-resistant tantalum, to increase the corrosion resistance of the back contact material.

In a corrosion experiment at elevated temperature (60°C) and high humidity (90%), the carved thin films (layer thickness: 300 nm) of molybdenum-tantalum exhibit a much better corrosion resistance, compared with pure molybdenum.

Especially on polymer-based substrates like polyimide, the high water and oxygen permeation can result in an increased corrosion of the CIGS back contact. With its higher corrosion resistance molybdenum-tantalum can minimise this effect, Plansee says.

Furthermore, on flexible substrates like stainless steel foil and polyimide the molybdenum-tantalum alloy can function as a corrosion resistant contact and protective layer. It effectively protects the backside of the stainless steel web during the selenisation step in the CIGS manufacturing process.