Synthesis of nanocrystalline CdS thin films in PVA matrix

Abstract

Nanocrystalline thin films of CdS are deposited on glass substrates by chemical bath deposition technique using polyvinyl alcohol (PVA) matrix solution. Crystallite sizes of the nanocrystalline films are determined from broadening of X-ray diffraction lines and are found to vary from 5⋅4-10⋅2 nm. The band gap of the nanocrystalline material is determined from the UV spectrograph. The absorption edge is shifted towards the lower wave length side (i.e. blue shift) and are found to be within the range from 2⋅48-2⋅8 eV as grain sizes decrease from 10⋅2-5⋅4 nm. This is also supported by the spectral response curves. An increase of molarity decreases the grain size which in turn increases the band gap.

Annealing Effect of Temperature on the Optical Properties of Nanostructure CdS Films

“…The reorganization of the film particles and self-oxidation are the temperature dependence parameters that affect the band gap. These values of band gap obtained are in close agreement to the previous studies by Ezema et al, Cetinnorgu et al and Devi et al [13,16,17]. C, the reflectance decreases with increasing wavelength toward VIS-NIR regions until a total sharp fall of reflectance value is reached then a sudden rise in reflectance is observed.…”

The effect of annealing temperature on the structural, optical, and electrical properties of CdS films

“…The as-deposited and annealed CdS films at low temperature (T < 623 K) exist in two crystalline phases: cubic (C) phase (zinc blende-type, JCPDS 06-0314) and hexagonal (H) phase (wurtize-type, JCPDS 10-0454), in line with the literature. 8,15,16,24,[32][33][34][35] Annealing leads to an overall improvement in the intensity of the peak heights, indicating that increasing annealing temperature increase the crystallinity of the film. By increasing the annealing temperature, the hexagonal phase becomes dominant and finally at T = 823 K the structure becomes 100% hexagonal phase.…”

“…6 For increased efficiency of solar cells, a semiconductor with optimum band gap, low resistivity, and high absorption coefficient is required. 7 Naturally, many different synthesis processes have been tried such as spray pyrolysis, 8,9 vacuum evaporation, 10 metal organic chemical vapor deposition, 11 and chemical bath deposition. 7,[12][13][14][15][16][17][18][19][20][21][22] Among these techniques, chemical bath deposition (CBD) is a low-cost and suitable technique to prepare high quality, well adhered film reproducibly.…”

Investigation of Structural and Spectroscopic Properties of Nanostructured CdS Films

“…4. The absorption band at 3435.61 cm -1 is attributed to the O-H stretching vibration of water molecule [19]. The band at 2932.17 cm -1 is due to C-H stretching.…”