Characterization of Physical Properties of Thermally Evaporated Doped CdS Thin Films for Photovoltaics

Abstract

Polycrystalline thin films of Cadmium Sulfide (CdS) have been extensively studied for application as a window layer in CdTe/CdS and CIGS/CdS thin film solar cells. Higher efficiency of solar cells is possible by a better conductivity of a window layer, which can be achieved by doping these films with suitable elements. CdS thin films were deposited on properly cleaned glass substrate by thermal evaporation technique under vacuum2×10-5mbar. Films were structurally characterized by using X-ray diffraction. The X-ray diffraction spectra showed that the thin films were polycrystalline in nature. Aluminum was doped chemically in as deposited and annealed thin films by immersing films in AlNO33.9H2O solutions respectively. Comparison between the effects of different doping ratios on the structural and optical properties of the films was investigated. Higher doping ratios have improved the electrical properties by decreasing the resistivity of the films and slightly changed the bandgap energy Eg. The grain size, strain, and dislocation density were calculated for as-deposited and annealed films.

Optical and electrical studies of CdS thin films with thickness variation

“…The SEM image of the as-deposited CdS thin film also demonstrates roughness 26 The slopes of conductivity v/s temperature have been shown as shown in Fig. 7.…”

“…The study of surface morphology of thin film provides useful and valuable information on shape, themselves for bigger grains. The coalescences play a vital role in CdS thin films when the thickness is increased, small grains coalesce with each other when due to ad-atoms [26][27][28][29] . These atoms may displace from interstitially or Cd and S atoms interchange their positions which is also changes the composition of as-deposited CdS thin films.…”

Critical Review on Crystal Orientation Engineering of Antimony Chalcogenide Thin Film for Solar Cell Applications

“…[ 12 , 13 , 14 , 15 ] The electron diffusion length in the [001]‐oriented (Sb 4 Se 6 ) n ribbons is approximately five times longer than that in the [221]‐oriented ribbons; thus, the [001] orientation is more conducive to improving the device performance. [ 16 ] In addition, [001]‐oriented films have a higher growth rate along the ribbon direction, such that when the lateral strain generated between the (Sb 4 S(e) 6 ) n ribbons exceeds the tolerance range of the van der Waals forces during deposition, the films tend to transform into a nanorod array, which is a common structure in [001]‐oriented films. [ 17 ] The [001]‐oriented nanorod array structured films reduce reflectivity and enhance light harvesting, which is beneficial to the performance of photovoltaic devices.…”