We have studied the initial stages of nucleation and growth of ZnS and ZnO on glass and tin oxide coated glass in chemical baths containing thiourea as a source of sulfide ions. The results are used to comment on strategies for the deposition of ZnS and related ternary materials.

Zinc telluride has the potential of being a low-cost, environmentally stable, lowresistance and easily manufacturable back contact for CdS/CdTe solar cells. Close Spaced Sublimation (CSS) technique is used to deposit thin films of ZnTe. The results are reported in this study.

The effects of substrate temperature and film thickness on the structural properties of the deposited thin films are studied. X-ray diffractograms show that all the films prominently exhibit presence of (111) and (200) orientations. However, the degree of the preferred orientation changes as a function of the film thickness. Increase in film thickness reduces the preferential orientation.

The as deposited ZnTe thin films, being that of p-type semiconductor, are highly resistive. In order to effectively use these as contact to CdS/CdTe solar cells, they are made more conductive by doping copper. The doping is effected by dipping the films in alcoholic solution of copper chloride, followed by air annealing at 200°C. The resistivity of all the doped films drops drastically in the initial 10 minutes of annealing. The extent of doping is controlled by varying the dipping time.

The effects of substrate temperature, film thickness and doping, on the stoichiometry of the films, are studied using Atomic Absorption Spectroscopy (AAS).

Indium Tin Oxide (ITO) thin films with low resistivities of 0.1 ∼0.2 mΩ-cm were deposited on various substrates such as YSZ, glass, and ZnO buffered glass by pulsed laser deposition (PLD). The X-ray rocking curve of crystalline (200) ITO films grown on (100) YSZ had a FWHM as narrow as 0.08°. ITO films grown on ZnO (0001) buffered glass had an single (222) orientation and the X-ray rocking curve had a FWHM of 2. 1°. Ultrathin ITO films of 3.6nm were fabricated on YSZ and their electrical properties were measured from 10K-300K. ITO films fabricated on ZnO buffered glass and bare glass were characterized by Hall effect measurements as a function of temperature. The results indicate that the resistivity of ITO films grown by PLD does not depend on the orientation or the structure of the thin film. The resistivity is dominated by impurity scattering in the range of 10K-300K. We show that ZnO/glass is a good alternative to bare glass for producing commercial ITO films.

Tin sulfide and a related novel compound, tin oxysulfide, thin films were deposited from the aqueous solution containing tin (11) chloride and thiourea by a spray pyrolysis technique. The constituent atoms of the thin films have merits of nontoxicity and availability. Physical and photovoltaic properties of both films were also investigated. It has, therefore, been considered that these two compounds become a promising absorbing layer for solar cell on account photovoltaic ability with high absorption coefficient and appropriate bandgap energy.

Thin films of CdS were prepared from an solution containing Cd(Ac)2, NH4OH, NH4Ac and (NH2)2CS for solar cells. Growth rate of CdS films was increased with increasing temperature of reactive solution and with decreasing concentration of NH4OH. Optical transmittances were more than 60% independent with temperature and concentrations and was changed with thickness of CdS films. Grown films mostly showed the presence of polycrystallines with mixed cubic and hexagonal phases, but showed the hexagonal preferred phases in some growth condition. The resistivities of CdS were decreased by doping boron from 104 to 101 order(Ω - cm) and the critical amount of dopant was 5 × 10− .mol %

We have investigated CdS thin films as possible passivating window layers for InP. The films were deposited on single crystal InP by chemical bath deposition (CBD). The film thickness, as optically determined by ellipsometry, was varied from 500 to 840Å. The film morphology was investigated by high resolution scanning electron microscopy (SEM), whereas the film microstructure was studied by X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM). Most of the films were fine-grained polycrystalline CdS, with some deposition conditions resulting in epitaxial growth. Cross-sectional TEM examination revealed the presence of interface contaminants. The effect of such contaminants on the film morphology and microstructure was studied, and various approaches for InP surface cleaning/treatment were investigated. The epitaxial films were determined to be hexagonal on both the (111) and (100) InP substrates; however, they were heavily faulted.

Multilayer assemblies of epitaxially-grown, Ill-V semiconductor materials are being investigated for use in thermophotovoltaic (TPV) energy conversion applications. It has been observed that thick, highly-doped semiconductor layers within cell architectures dominate the parasitic free-carrier absorption (FCA) of devices at wavelengths above the bandgap of the semiconductor material. In this work, the wavelength-dependent, free-carrier absorption of p- and n-type InGaAs layers grown epitaxially onto semi-insulating InP substrates has been measured and related to the total absorption of long-wavelength photons in thermophotovoltaic devices. The optical responses of the TPV cells are then used in the calculation of spectral utilization factors and device efficiencies.

The perspectives for solar cell application of structural inhomogeneous a-Si:H films deposited at high growth rates (∼10–20 Å/s) from 100% SiH4 in low frequency (LF) 55kHz glow discharge plasma have been investigated. In this case the influence of structural inhomogeneity on dark dc and photoconductivities and light-induced defect generation kinetics (Staebler-Wronski effect, SWE) in a-Si:H films have been studied. The microstructure of films was investigated by IR spectroscopy analysis. Microstructural parameter R=[SiH2]/([;SiH]+[SiH2]), was used for the quantitative characterization of structural inhomogeneity in the material bulk.

It was found that Fermi level position is fixed by deep defect states and does not depend on microstructure parameter R. The comparative analysis of photoconductivity modeling and ESR measurements have shown that recombination in a-Si:H films is controlled by neutral dangling bonds and doesn't depend on parameter R. Meanwhile it was found that the kinetics of light-induced defect generation was controlled by SiH2 or clustered SiH groups content. Thus, the above results allow to perform an independent control of stability and electronic properties of a-Si:H films deposited in LF glow discharge plasma.

In this work a-Si:H/c-Si heterostructures with good electronic properties of a-Si:H were prepared by 55 kHz Plasma Enhanced Chemical Vapor Deposition (PECVD). Currentvoltage and capacitance-voltage characteristics of a-Si:H/c-Si heterostructures were measuredto investigate the influence of low frequency plasma on the growing film and amorphous silicon/crystalline silicon boundary. It was established that the interface state density is low enough for device applications (<2.1010 cm−2). The current voltage measurements suggest that, when forward biased, space-charge-limited current determines the transport mechanism in a- Si:H/c-Si heterostructures, while reverse current is ascribed to the generation current in a-Si:H and c-Si depletion layers.