Investigation of non-aqueous electrodeposited CdS/Cd1−xZnxTe heterojunction solar cells

Abstract

Polycrystalline Cd1−xZnxTe solar cells with efficiency of 8.3% were grown by cathodic electrodeposition on glass/ITO/CdS substrates using non-aqueous ethylene glycol bath. The deposit is characterised versus the process conditions by XRD and found to possess a preferred (1 1 1) orientation on Sb doping in the electroplating bath. The surface morphology of the deposit is studied using atomic force microscope. The average RMS roughness for the ternary film was higher than that for the binary CdTe. Optical properties of the films were carried out to study the band gap and calculation of molar concentration ‘x’. The effects of Sb doping in CdS/Cd1−xZnxTe heterojunctions have been studied. The short circuit current density (c) was found to improve and series resistance (Rs) reduced drastically upon Sb doping. This improvement in Jsc is attributed to an increase in quantum efficiency. The evaluation of solar cell parameters was also carried out using the current–voltage characteristics in dark and illumination. The best results were obtained when 2×10−3 M ZnCl2 along with antimony were present in the deposition bath. Under AM 1.5 conditions the open circuit voltage, short circuit current density, and fill factor of our best cell were Voc=600 mV, Jsc=26.66 mA/cm2, FF=0.42 and efficiency, η=8.3%. The carrier concentration and built-in potential of Cd1−xZnxTe calculated from Mott–Schottky plot was 2.72×1017 cm−3 and 1.02 eV.