Effects of CdCl2 Treatment on Physical Properties of CdTe/CdS Thin Film Solar Cell

Abstract

We report CdTe, CdS, and ITO thin films on glass substrates for solar cell fabrication by closed space sublimation and chemical bath deposition. CdTe and CdS thin films were sublimated to chemical treatment at 25°C in a saturated CdCl 2 solution (1.04 g/100 ml methanol) and heat treated at 400°C for 30 minutes. Indium tin oxide and tellurium films were analyzed by spectrophotometer and scanning electron microscopy. It has been observed that solar cell performance can be improved by depositing a CdCl 2 layer on the CdTe/CdS layers. The optical, structural, and morphological changes of CdTe and CdS surfaces on CdTe/CdS/ITO/glass solar cells due to CdCl 2 solution treatment followed by annealing for 400°C were studied. Optical analysis showed about 15% decrease in transmittance after CdCl 2 heat treatment in case of CdTe thin film, whereas CdS thin film demonstrated an increase of about 10-15% transmittance after CdCl 2 heat treatment. Similarly, a decrease in band gap values was found for both CdTe and CdS thin films after CdCl 2 heat treatment. XRD and SEM results of CdCl 2 heat-treated CdTe and CdS samples showed recrystallization, reorientation, and progressive increase in grain size. The grain sizes of CdTe and CdS samples demonstrated an increase of about 0.2 µm.