Cadmium telluride films for lightweight solar cells for space and terrestrial applications

Deposition of cadmium telluride (CdTe) films on steel foil substrates was investigated. Adherent CdTe films were vacuum evaporated and a growth rate of 3 nm/sec was obtained at a substrate temperature of 533 K. As deposited films exhibited a preferred (111) orientation. A tellurium interlayer between CdTe and steel yielded larger grains in CdTe than a gold interlayer. Annealing of CdTe films at 823 K increased the grain size and reduced the film resistance; it also tended to transform p‐type CdTe into n‐type. This was attributed to the diffusion of tellurium from CdTe into steel and diffusion of iron from the steel substrate into the CdTe film. This diffusion was observed using energy dispersive X‐ray analysis. A photovoltage was obtained by depositing CdS on top of p‐CdTe and a V_oc of 360 mV was obtained.