Dhananjaya Kekuda

CuO/ZnO planar bilayer heterojunction grown by reactive dc magnetron sputtering

In the present article, we have investigated the possibility of utilizing cupric oxide as the promising absorber layers for the construction of oxide solar cells. The effect of argon to oxygen ratio on the structural and optical properties of copper oxide thin films is described. From the optical characterization, it was evident that band gap energy can be tuned by varying the argon to oxygen ratio (Ar:O2) during deposition. Zinc oxide thin films with high transmittance were utilized as n-type counterparts for the cupric oxide absorber layers. The device structure with the configuration glass/Cu/CuO/ZnO/Al was characterized through dark and illuminated current–voltage (I–V) characteristics. Ohm’s law prevailed in the low field regime and space charge limited conduction followed in the high field region as observed from dark I–V characteristics.

Flexible cadmium telluride/cadmium sulphide thin film solar cells on mica substrate

Polycrystalline thin film II–VI compound semiconductors of cadmium sulfide (CdS) and cadmium telluride (CdTe) are the leading materials for the development of cost effective and reliable photovoltaic systems. The two important properties of these materials are its nearness to the ideal band gap for photovoltaic conversion efficiency and they have high optical absorption coefficients. Usually thin film solar cells are made by hetero-junction of p-type CdTe with n-type CdS partner window layer. In this article, we have deposited CdTe films on mica substrates using thermal evaporation technique and CdTe/CdS junction were developed by depositing a thin layer of CdS on to the CdTe substrate from chemical bath deposition method. The device was characterized by current voltage and photocurrent spectroscopy technique prior to the deposition of the transparent conducting layer. The devices were annealed in air at different temperatures and found that the device annealed at 673xa0K had better photovoltaic parameters. The efficiency of a typical device under 50xa0mWxa0cm−2 illumination was estimated as 4%.

Dependence of solution molarity on structural, optical and electrical properties of spin coated ZnO thin films

Zinc oxide (ZnO) thin films were deposited on glass substrates through spin coating technique. Zinc acetate dihydrate, monoethanolamine and 2-methoxyethanol were used as the starting material, stabilizer and solvent, respectively. The effect of precursor concentration on the structural, optical and electrical properties of ZnO thin films is investigated. The X-ray diffraction studies reveal that all the films are polycrystalline in nature with preferred (002) orientation with crystallite size ranging from ~25 to 32xa0nm. Atomic force microscopy images infer the columnar growth of the films. From the optical measurements it was found that there was a marginal decrease in the band gap energy with increase in molarity up to 0.7xa0M. Optical constants and thickness of the films were found with the help of Swanepoel envelope method and were verified through ellipsometric measurements. Electrical resistivity of the grown films was found to be in the range 29–244xa0Ωxa0cm, with a lowest value obtained for the films grown at 0.7xa0M. Carrier concentration of the grown films has also followed a similar trend. On the other hand, the Hall effect mobility (~400xa0cm2/Vs) was highest for the films grown at 0.7xa0M. Such high values make these films potential candidates for photovoltaic and display applications.

Thickness and oxygen partial pressure dependence on optical band gap of indium oxide by reactive evaporation method

Indium oxide film is deposited by reactive evaporation of indium in the presence of oxygen gas onto an unheated glass substrate. It was found that thickness of the film and partial oxygen pressure during the deposition affects the optical properties of the indium oxide thin film. We studied the optical band gap for different thickness and partial pressure keeping a constant annealing temperature. It was found that the band gap varies from 3.5 to 3.8eV, as thickness of the film increased. The band gap energy had also shows the similar trend and it was also studied as a function of annealing temperature. A systematic investigation of the optical band gap as a function of thickness and oxygen partial pressure at different annealing temperature was carried out.

Optical Properties of Zinc Oxide (ZnO) Thin Films Prepared by Spray Pyrolysis Method

Zinc oxide (ZnO) thin films were deposited on the glass substrates using Zinc acetate dehydrate solution through spray pyrolysis method. The films were obtained by spraying 0.05M concentrated solution at a rate of 0.5ml for 10 min and were deposited at different substrate temperatures ranging from 473K to 673K. A comprehensive study was carried out to realize the effect of substrate temperatures and subsequent annealing on optical properties of the ZnO thin films. It was observed that the band gap energy decreases with increases the substrate temperature and annealing. Optical constants such as the refractive index n and extinction coefficient k were determined from transmittance spectrum in the ultravioletvisible (UVVIS) regions by Swanepoel envelope method and crystallinity was confirmed by Urbach tail and atomic force microscope images.