Study on the optoelectronic properties of the heterostructure ZnO/CdS/CdTe for its applications in CdTe solar cells

This work focuses on the development of a photovoltaic cell based on the CdS/CdTe heterostructure, the incorporation of a high resistivity ZnO layer was proposed, which could reduce the interfacial current density between the front contact and CdS in the device. CdS films on glass/SnO₂:F/ZnO substrates were obtained by chemical bath technique by varying the precursors concentrations. Subsequently, CdTe film was deposited on glass/SnO₂:F/ZnO/CdS heterostructure by close space sublimation to obtain an n-p union solar cell. Structural and optoelectronic characterization allowed the determination of the critical growth parameters under which the CdS film's properties were improved. Structural characterization performed by X-ray diffraction (XRD) and Raman spectroscopy suggests that CdS films have a mixture of cubic and hexagonal phases. CdS films have an optical transmittance maximum of 80%, in the visible region. Electrical measurements confirm the n-type conductivity of the CdS films. For the CdTe film, the cubic phase was identified by XRD. Raman characterization showed modes attributed to a Te-rich surface due to the thermal treatment. The device efficiency increases by 2% with the incorporation of a ZnO high resistive layer compared to the reference cells.