Thin Film Cadmium Zinc Telluride Solar Cells

A process for fabricating thin film heterojunction solar cells with cadmium zinc telluride (Cd_1-xZn_xTe) absorbers is described. Cd_1-xZn_xTe films with composition from 0lesxles0.6 were deposited by a simple vapor transport (VT) process at 550degC onto moving CdS-coated substrates. Post-deposition thermal treatment in halide vapor ambient yielded high photocurrent, limited primarily by window layer optics. Similar cell performance is demonstrated for ZnCl₂ and CdCl₂ vapors using treatment protocols which retain film composition. Solar cell efficiency >12% has been achieved for cells with 0 < x < 0.10 (1.50 eV < E_g < 1.58 eV) and efficiency > 8.5% has been achieved for cells with 0.1 < x < 0.3 (1.58 < E_g < 1.60eV). No enhancement of V_oc with increasing band gap has been found and may be related to window-absorber interfacial reactivity and resulting junction non-uniformity