Electrosynthesis and characterizations of NiTe2 thin films for photoelectrochemical (PEEC)cell

• Auteur principal: Abdul Aziz, Mohd Zaidan
• Format: Thèse
• Langue: anglais; anglais
• Publié: 2015
• Sujets: T Technology (General); TR Photography
• Accès en ligne: http://eprints.utem.edu.my/id/eprint/16814/1/Electrosynthesis%20And%20Characterizations%20Of%20NiTe2%20Thin%20Films%20For%20Photoelectrochemical%20%28PEEC%29Cell.pdf; http://eprints.utem.edu.my/id/eprint/16814/2/Electrosynthesis%20and%20characterizations%20of%20NiTe2%20thin%20films%20for%20photoelectrochemical%20%28PEEC%29cell.pdf

This project emphasises the synthesis of the stoichiometric nickel telluride, NiTe2 thin films as the solar or photoelectrochemical (PEC) cells absorbent. Nickel telluride thin film in the form of transition metal chalcogenide, MX2 (M = transition metal, X = chalcogenide [S, Se, Te]) offers promising properties in such application. Electrodeposition has been chosen to deposit the film onto the substrate due to its advantages such as possibility of large scale deposition, minimum waste of components, easy monitoring of deposition process and large area deposition. Using this technique, nickel telluride thin films were cathodically deposited onto indium tin oxide (ITO) glass substrates. By changing the deposition parameters such as deposition potential, additive concentration and deposition time throughout the film synthesis, high quality films having good adhesion, smooth surface and uniform distribution were acquired. It was found that the optimal films parameters are in the presence of 0.1 M triethanolamine (TEA), 20 min deposition time and -1.0 V potential based on a few electrodeposition experiments. Structural characterisation through X-ray diffraction studies revealed the presence of hexagonal structure of nickel telluride, NiTe2 thin film with lattice parameters a = b = 0.3843 nm and c = 0.5265 nm. Scanning electron micrographs exposed that the films was pinhole-free, compact and smooth, showing a granular structure having almost spherical shape with well-defined grains. On the other hand, the film composition was confirmed to present both nickel and tellurium complying the correct stoichiometry by using Energy-dispersive X-ray (EDX). The optical absorption analysis employed by Shimadzu 1700 UV-Vis Spectrophotometer has confirmed that the energy bandgaps of NiTe2 thin film lie within the semiconductor range (1 - 1.2 eV) with indirect nature. The positive Mott-Schottky plots indicates that NiTe2 thin film is negatively charged (n-type conductivity), having more electrons (e-) than holes (h+). The derivation of semiconductor parameters like doping density, ND, built in voltage, Vb (band bending) and flat band potential, Vfb obtained from semiconductor studies play significant part in determining the conversion efficiency of photoelectrochemical (PEC) cell. The results attained from these characterisations have verified the compatibility of NiTe2 as solar cell green alternative materials.