F. Fauzi

Development of ZnTe layers using an electrochemical technique for applications in thin-film solar cells

Zinc telluride layers were grown by an electrochemical technique using acidic and aqueous solutions containing ZnCl2 and TeO2. The layers were deposited on glass/fluorine-doped tin oxide substrates using a two-electrode system. The deposited ZnTe layers were characterized using x-ray diffraction, x-ray fluorescence, Raman spectroscopy, optical absorption, photoelectrochemical cell measurements, scanning electron microscopy and 3D-atomic force microscopy (3D-AFM) for the structural, optical, electrical and morphological properties. The electrodeposited ZnTe layers grow as columns, and have cubic crystal structure, the band gap in the range of (2.00–2.20) eV and p-type electrical conductivity. Surface morphology studies using SEM indicate the presence of two types of material clusters varying in size up to ~125 nm. 3D-AFM studies with higher magnification show that the material tends to grow as columns with different sizes leaving gaps in between in some areas.

Study of Fermi level movement during CdCl2 treatment of CdTe thin films using Ultra-violet Photoemission Spectroscopy

The CdCl2 treatment used in the development of high efficiency CdTe solar cells is an essential processing step but remains fully unexplored. What really happens during this treatment is not yet fully understood. The changes in doping concentrations during this processing step are a key parameter to investigate. Determination of the position of the Fermi level (FL) is a good method to explore these changes and therefore photoelectrochemical cell method and ultraviolet photoelectron spectroscopy method have been used to investigate these trends. Four different CdTe layers prepared by electroplating have been used for this investigation. The overall observations indicate the settling down of the FL in the upper half of the bandgap after CdCl2 treatment.

Study of Fermi level position before and after CdCl2 treatment of CdTe thin films using ultraviolet photoelectron spectroscopy

The CdCl2 treatment used in the development of high efficiency CdTe solar cells is an essential processing step but remains fully unexplored. What really happens during this treatment is not yet fully understood. The changes in doping concentrations during this processing step are a key parameter to investigate. Determination of the position of the Fermi level (FL) is a good method to explore these changes and therefore photoelectrochemical cell method and ultraviolet photoelectron spectroscopy method have been used to investigate these trends. Four different CdTe layers prepared by electroplating have been used for this investigation. The overall observations indicate the settling down of the FL in the upper half of the bandgap after CdCl2 treatment.

Electrodeposition and characterisation of ZnTe layers for application in CdTe based multi-layer graded bandgap solar cells

Zinc Telluride (ZnTe) thin films have been deposited on glass/conducting glass substrates using low-cost aqueous electrodeposition (ED) method. The structural, optical and morphological properties of the resulting films have been characterized using X-ray diffraction (XRD), spectrophotometry and Scanning Electron Microscopy (SEM). It has been confirmed by XRD technique that the deposited layers are nano- and polycrystalline mixture for as deposited layers. Photoelectrochemical (PEC) studies revealed that the layers are p-type in electrical conduction. Optical absorption measurement has been used for the bandgap determination of the deposited layers. The bandgap of the polycrystalline ZnTe layers are in the range (2.65 – 2.75) eV for the ZnSO4 precursor, and (2.70 – 2.87) eV for the ZnCl2 precursor instead of (2.21 – 2.26) eV reported for crystalline ZnTe. This increase may be due to the quantum effect which confirmed by the absence of strong XRD peaks from these layers and/or inclusion of ZnO in the deposited layers.