A comparison of window/buffer layer materials for CdTe thin film modules using environmental risk assessment

The chemical bath deposition of both cadmium sulphide (CdS) and zinc selenide (ZnSe) window layers has been compared and assessed in terms of the major reactants, transition materials, by-products and waste, using environmental risk assessment techniques. Data are presented from experimental measurements of CdS chemical bath deposition processes, showing that nonvolatile carcinogens such as CdS and thiourea can be dispersed into the gaseous environment via the aerosols produced by hot deposition baths. The paper compares the environmental implications of using CdS, currently the traditional window material, or ZnSe, the most promising of the available alternatives. In both cases, careful management and control of gaseous emissions, waste treatment and PV module recycling is necessary to meet the strict environmental criteria now demanded by US and EU legislation.