Preparation and characterization of ZnTe as an interlayer for CdS/CdTe substrate thin film solar cells on flexible substrates

ZnTe thin films have been prepared on Mo-coated stainless steel substrates by the close spaced sublimation (CSS) technique. Cu-doped ZnTe (ZnTe:Cu) films are prepared by immersing the as-deposited samples in a CuCl–H2O solution. The structural and morphological properties of the ZnTe films as a function of substrate temperature are investigated using X-ray diffraction and scanning electron microscopy. CdS/CdTe solar cells with and without the ZnTe and ZnTe:Cu interlayers are prepared and characterized with current–voltage (J–V), spectral response, and capacitance–voltage measurements. The structural and morphological properties of the ZnTe films prepared by CSS are found to be strongly influenced by the substrate temperature. The ‘roll-over’ behavior in the J–V characteristics of the CdS/CdTe solar cells due to a Schottky barrier at the back contact can be eliminated using ZnTe as the interlayer. Preliminary results on the application of ZnTe:Cu films suggest that the open circuit voltage and fill factor can be further improved, depending on processing conditions.

► Thin film CdTe solar cells on flexible stainless steel substrates are prepared.
► Using ZnTe can eliminate the ‘roll-over’ behavior in the current–voltage curve.
► Incorporating Cu can further improve the open circuit voltage and fill factor.