Publication

Abstract : Spray pyrolysis deposition (SPD) based CdTe/CdS thin film heterojunction was fabricated for energy harvesting application.CdTe thin film of ~3.3 µm thickness was deposited onto CdS films of different thickness values. In the SPD process, we used cadmium nitrate tetrahydrate and tellurium dioxide as precursors for CdTe thin films.For CdS, CdCl2 and thio-urea were used as precursors. The SPD process was carried out at 400oC and 200oC for CdTe and CdS thin films respectively. In the heterojunction, CdTe acts as a major photo-active semiconductor while CdS is a windfow layer. Raman spectroscopic measurement confirmed CdTe and CdS thin films with their characteristic peaks. CdS exhibits Raman active peaks at 296.9 cm-1, 599.8 cm-1, 890.6 cm-1 representing 1LO, 2LO and 3LO modes respectively. Photo-responsive studies on CdTe and CdS thin films were characterized in the spectral range of 300 nm-1000 nm. As a window layer for photovoltaic application, CdS layer exhibit an absorption in the range of 300 nm-500 nm while CdTe showed a dominant photo-absorption in the spectral range of 300-900 nm and extended upto 1000 nm. Optical absorption of thin films of CdTe and CdS, measured individually, confirm that the combination would perform optically promissing. Tauc plot technique was applied onto the measured transmittance spectra of the CdS and CdTe thin films and the optical bandgap values were found to be 2.5 eV and 1.5 eV respectively. We observe that spray pyrolysis yields CdTe and CdS thin films with smooth and uniform surface. Further studies focussing on the effect of grain/grain boundaries and light scattering particles on the performance of a heterojunction solar cell are under progress