This paper embodies the first report on the pulse reversal deposition of CdSe thin films. The as-deposited and heat treated films were characterized by XRD, optical absorption spectroscopy and electrical properties. The polycrystalline deposits of CdSe obtained indicated a hexagonal structure after heat treatment at 550°C. From the otpical absorption studies the bandgap was found to be 1.70 eV and absorption co-efficient of 104 cm-1 were obtained. At an illumination of 80 mWcm-2 conversion efficiencies of 5.56% and 6.74% were obtained for the photoelectrodes without and with pulse reversal.
Thin films of cadmium selenide were prepared for the first time by spray pyrolysis technique using non-toxic selenosulphate on clean glass, titanium and conducting glass substrates, at substrate temperature in the range of 300 to 500 degree(s)C. The films were characterized by X-ray diffraction, optical absorption, photo conductivity and photo electro chemical studies.
Indium tin oxide (ITO) film has been prepared by sequential vacuum deposition of indium and tin on plain glass followed by oxidation at temperatures around 400 degrees - 650 degrees Celsius. By a proper control of the time of evaporation and the heating current the concentration of vacuum evaporated indium was maintained constant and tin concentration was varied in the range of 10 - 60% by weight. ITO films with good optical and electrical properties can be obtained by adjusting the ratio of Sn:In in the range of 1:9 to 1:35 after heat- treatment at 400 degrees to 600 degrees Celsius. The films exhibit a sheet resistance of 20 ohms per square with an optical transmission of 60% at 500 nm when the Sn:In ratio was maintained at 1:9. The film was found suitable for ITO/Si solar cells and as substrates for photo anodes in PEC cells.
Lead chalcogenides are well-known photoconductors in the infrared region. Lead sulfide detectors occupy an important position among infrared detectors owing to their high sensitivity in the near infrared region (1 - 3.2 microns), room temperature operation, low noise and ease of preparation. In this paper, we report for the first time the preparation of infrared sensitive photoconductive lead sulfide films by the swab plating technique. Adherent, non-porous `p' type lead sulfide films of thickness 3 - 4 microns were obtained. These films, after heat- treatment at 550 degree(s)C, showed a dark resistance of 25 - 30 kilo-ohms with a photosensitivity of 0.28. The films have been characterized by XRD, optical and photoconductivity measurements.
The photosensitivity of lead chalcogenides in the IR region has been known for a long time. These detectors exhibit wide range of electrical characteristics. A cheap and easy chemical bath deposition process has been utilized to deposit PbS onto glass substrates. Well adherent nonporous `p' type PbS films of thickness 1 - 1.5 microns were obtained. These films, after heat treatment, showed a dark resistance of 0.5 - 1 M(Omega) with a high signal-to-noise ratio of 1000 with a D* (800 degree(s)C, 500 Hz, 2 Hz) of 2.6 X 1010 cm Hz1/2 W-1.
Pulse deposition at room temperature was applied to obtain CdSe thin films from an aqueous bath consisting of CdSO4 and SeO2 on titanium substrates, employing a range of current densities from 80 - 550 mA cm-2. The films were polycrystalline with a hexagonal structure. The pulse deposited films were observed to show greater uniformity and large grain sizes than the conventionally deposited ones. The films, heat-sensitized and vacuum annealed, showed a flat-band potential of -1.17 V (SCE) and a high energy conversion efficiency of 6.3% at 60 mW cm2 in polysulphide redox after photoetching. The optical band gap was 1.7 eV.
Studies on slurry painted CdSexTe1-x photoactive films prepared from CdSe and CdTe synthesized by a low temperature wet process are reported. The films on Ti sub- strates, heat treated at 550°C in argon were polycrystalline with the bandgap increasing and room temperature conductivity decreasing with the x value. In poly- sulphide electrolyte, the films with a composition CdSe0.5Te0.5 gave a Voc of 425 mV, Jsc of 8.5 mA cm-2, FF of 0.54 and η of 3.25% at an illumination of 60 mW cm-2.
Thin films of cadmium selenide were prepared for the first time by a selective
plating technique on conducting glass and titanium substrates. The films were
characterised bymeans of x-ray diffraction, scanning electron microscopy, optical
absorption, photoconductivity, and photoelectrochemical (PEC) studies.
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