Cd_(1-x)Mg_xTe thin films and top-cells for possible applications in tandem solar cells

摘要

Thin films of the ternary material Cd_(1-x)Mg_xTe were developed by the co-evaporation of CdTe and Mg at substrate temperatures ranging from 300 to 400 ℃. Films with band gap close to 1.6 eV were deposited on both corning glass as well as CdS/Tec7 substrates depending on the end use. Films were characterized for structure, morphology, composition, optical and optoelectronic properties. Similar to CdTe based solar cells, Cd_(1-x)Mg_xTe/CdS devices also showed dependence on the vapor chloride annealing temperature and Cu diffusion process. Stability of the material during chloride annealing hampers high temperature annealing and recrystallization. With improved contact processing and post deposition treatments we were able to fabricate Cd_(1-x)Mg_xTe/CdS devices with efficiency over 7.5%.