In the present work, undoped (SnO 2) and fluorine-doped tin oxide (FTO) thin films were prepared by sol-gel process using a solution composed of (SnCl 2 , H 2 O), (NH 4 F), and ethanol mixture. The fluorine concentration effect on structural, optical and electrical properties of SnO 2 films is investigated. The electrical properties of FTO films prepared by sol gel remain relatively lower than the ones deposited by other techniques. In present paper, we try to elucidate this difference. Films composition and the FTIR analysis, of films and formed precipitate during film growth, indicate that few amounts of fluorine are incorporated in SnO 2 network, most of fluorine atoms remain in the solution. The films resistivity is reduced from 1.1 Ω•cm for undoped films to 3 × 10 −2 Ω•cm for 50 wt.% doped FTO, but remains higher than the reported ones in the literature. This high resistivity is explained in terms of fluorine bonding affinity in the solution.
Nanocrystalline zinc sulfide thin films were prepared on glass substrates by chemical bath deposition method using aqueous solutions of zinc chloride, thiourea ammonium hydroxide along with non-toxic complexing agent trisodium citrate in alkaline medium at 80 • C. The effect of deposition time and annealing on the properties of ZnS thin films was investigated by X-ray diffraction, scanning electron microscopy, optical transmittance spectroscopy and four-point probe method. The X-ray diffraction analysis showed that the samples exhibited cubic sphalerite structure with preferential orientation along 2 0 0 direction. Scanning electron microscopy micrographs revealed uniform surface coverage, UV-Vis (300 nm to 800 nm) spectrophotometric measurements showed transparency of the films (transmittance ranging from 69 % to 81 %), with a direct allowed energy band gap in the range of 3.87 eV to 4.03 eV. After thermal annealing at 500 • C for 120 min, the transmittance increased up to 87 %. Moreover, the electrical conductivity of the deposited films increased with increasing of the deposition time from 0.35 × 10 −4 Ω·cm −1 to 2.7 × 10 −4 Ω·cm −1 .
In the present paper calculation of CuInSe2(CIS)/ CdS solar cell efficiency is presented. The influence of the thickness and the optical band gap of CdS and CIS layers on the solar cell performances are investigated. The thickness of CdS buffer layer, wh ich is generally neglected is taken into account. The solar cells performances calculat ions are based on the calculation, by means of developed software written with Matlab, o f photocurrent from the resolution of the well known three coupling equations: continuity equation for holes in the CdS (n -region) and fo r electrons in the CIS (p-region) and Poisson equation. The obtained results indicated that the solar cell efficiency can be improved by reducing the CdS thickness or by increasing the CIS thickness. The efficiency increasing rates are 0.01 %/ n m and 0.5 %/n m for CdS and CIS layer thickness respectively. The CdS layer alters the shorter wavelength of the solar spectrum, wh ile the CIS layer alters the longer wavelength. CIS layer optical band gap is the most crucial parameter by co mparison to the optical gap of CdS layer.
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