Formation of conductive CdO layer on CdS thin films during air heating

Abstract

A thin layer of CdO is formed on a chemically deposited CdS thin film through reaction with atmospheric oxygen during heating in air for 5-240 min at 370-500 • C. The sheet resistance of the film drops from about 10 13 -3.5 k (370 • C) and 470 (500 • C). From optical transmittance and reflectance spectra, the thickness of the CdO layer was found to be about 10 nm; the crystalline grain size is 12-25 nm, depending on the temperature and duration of heating; and the estimated electrical resistivity is 10 −4 -10 −3 cm. The optical bandgap of the CdS-CdO layer is effectively that of the underlying CdS thin film, about 2.45 eV in the annealed film. The CdS, which remains under the conductive CdO top layer, is photosensitive, with a photo-to-dark current ratio of 10 3 and crystalline grain diameter of about 10 nm in the case of a film heated at 500 • C for 5 min. These results are discussed in the context of window layers in solar cells.

Effects of air annealing on CdS quantum dots thin film grown at room temperature by CBD technique intended for photosensor applications

“…This deviation of band gap from 2.48 eV to 2.21 eV can be attributed to the change in crystallite size as a result of controlled annealing [28]. However, it was observed that the air annealing of the samples beyond 350 8C resulted in the formation of CdO on account of its oxidation [29]. The observed improvement in the crystallites of samples can be correlated with the optical study, reflecting red shift in optical band gap of the material which is justified by increased crystallite size and crystalline quality [30].…”

Synthesis and characterization of nanostructured semiconductors for photovoltaic and photoelectrochemical cell applications

“…The chemical bath employed was already reported by other authors from our center [18,19]. The bath composition consisted of 75 ml of 0.1 M Cd(NO 3 ) 2 , 45 ml of 1 M Na 3 C 6 H 5 O 7 , 6 ml of 14.4 M aqueous NH 3 , 15 ml of 1 M [SC(NH 2 ) 2 ] and the bath volume was adjusted to 300 ml by adding tri-distilled water.…”

An optimized multilayer structure of CdS layer for CdTe solar cells application

“…6, the survey spectra of sample A and B indicate that the CBD CdS contains oxygen, which may be one reason of the low band gap of CBD CdS layer [20,21]. Table 3 shows the performance of the solar cells.…”