Fluorine-doped Tin Oxide Films Research Articles

The degradation of fluorine doped tin oxide films in a hydrogen plasma

The effect of hydrogen plasma on the properties of transparent conducting fluorine doped tin oxide films has been studied. Exposure to hydrogen plasma results in the reduction of the film surface to elemental tin and suboxides of tin. The thickness of the reduced layer increases with increasing exposure to plasma and finally saturates to a thickness of 100 to 150 nm, having an extremely rough texture. The presence of the rough metal‐rich surface layer decreases the visible transmittance drastically due to increased reflectance and absorptance of the films. The sheet resistance of the films increases due to the formation of suboxide. Annealing of the plasma exposed film in oxygen results in a recovery of the transparency except when the film surface is severely damaged and remains extremely rough after the annealing treatment.

UV absorption studies of undoped and fluorine-doped tin oxide films

Abstract Tin oxide films undoped and doped with fluorine are prepared by a chemical vapour deposition technique involving the oxidation of SnCl2. For fluorine doping a mixture of trifluoroacetic acid and deionized water is used. The optical properties of these films are investigated in the UV region (225–350 nm). It is observed that for an undoped tin oxide the absorption edge lies at 3.71 eV. It is also observed that for fluorine-doped tin oxide films the absorption edge shifts towards higher energies, which is related to the Moss-Burstein shift. In the case of fluorine-doped tin oxide films, depending on the fluorine concentration, the absorption edge lies in the range 3.89–4.07 eV. Undoped and fluorine-doped tin oxide films show a direct transition at 4.03 eV and in the range 4.17–4.29 eV respectively, whereas the indirect transition for undoped and fluorine-doped tin oxide films occurs at 3.35 eV and in the range 3.55–3.67 eV respectively.

Fluorine-doped tin oxide—selenium heterojunction for photovoltaic conversion

Selenium, being a low-cost material and readily available in high purity form, is attracting interest for solar cell applications. It has been calculated theoretically [1] that selenium-based heterojunction solar cells can have an efficiency as high as 20%. Shaw and Ghosh [2] have reported that cells with efficiency better than 10% can be fabricated with selenium in the form of heterojunctions. The results on CdO-CdSe-Se and SnO2-CdSe-Se heterojunctions [2, 3] indicate a conversion efficiency of the order of 3%. Nakada and Kunioka [4] have developed an indium tin oxide (ITO)-selenium heterojunction solar cell having an efficiency of 3.3%. In this letter we report the results of fluorine-doped tin oxide (FTO)-selenium heterojunctions. Transparent FTO films were prepared on chemically and ultrasonically cleaned glass substrates using the spray pyrolysis technique described earlier [5]. The FTO films so obtained show optical transmittance of 84% for a wavelength of 540 nm with a sheet resistance of 10 f~/D at room temperature. No antireflection coating was done prior to deposition of FTO. High-purity selenium (99.999%) obtained from Nuclear Fuel Complex (India) was thermally deposited from a quartz crucible onto the FTO-coated glass slides kept at room temperature. On some of the samples, an ultrathin tellurium layer (1 to 5 nm) was deposited prior to selenium coating. The selenium film was intentionally grown as amorphous to have better control over thickness and surface morphology. A silver overlayer was grown on the selenium to give electrical contact and back-field reflectance. A conducting silver paste was used to take electrical contacts from the silver film. All the vacuum deposition was done in a Hind high-vacuum (India) coating unit 12A4 at a pressure better than 10 -5 torr using a liquid nitrogen trap. The thickness of the film was measured using an FECO interferometer. The selenium sandwich was subjected to thermal shocks at 200 ° C to convert high resistivity amorphous selenium to low resistivity polycrystalline selenium.

Experimental and Theoretical Results for Light Trapping in High Efficiency a-Si1-xCx:H/a-Si:H Solar Cells Prepared on Granular Tin Oxide.

ABSTRACTWe examine the morphology and optical properties of fluorine doped tin oxide films prepared by the chemical vapor deposition of tetramethyltin and tin tetrachloride and the influence of these properties on light trapping in amorphous silicon solar cells having the structure glass/SnO2 /P (a-Si1-xCx:H) -i-n/metal. Measured tin oxide properties include total and diffuse transmission as a function of wavelength, angular dependence of the scattered light, surface topography, and sheet resistance. Experimental quantum efficiency plots as a function of wavelength are presented and compared to computer calculations based on multilayer optics programs and measured optical constants. Using granular tin oxide, p-i-n cells 1 cm2 in area have been prepared with efficiencies exceeding 10%.

Sprayed films of indium tin oxide and fluorine-doped tin oxide of large surface area

In the study presented in this paper we attempted to optimize the transmission and resistivity of thin films 10 cm × 10 cm in area. The design of the system used is such that it is possible to control all the parameters affecting the formation of these layers. The nozzle moves above the substrate which is heated to a high temperature. The solution is pulverized by means of a neutral gas ( e.g. nitrogen) sothat it arrives at the substrate in the form of very fine drops. The layer thickness is monitored by observing the interference orders in the thin films, and so we can modify various parameters such as the speed of the solution, the dopant concentration and the substrate temperature whilst ensuring that the thickness is held constant.