Challa Nagesh

Date of Award


Degree Name

Master of Arts

First Advisor

Dr. K. K. Rao

Access Setting

Masters Thesis-Open Access


The photoconductivity spectra of ultra-pure single crystals of CdS in the range 500-575 nm, CdSe in the range 700-900 nm, ZnSe in the range 420-570 nm and ZnS in the range 300-450 nm have been studied using an improved A.C. method of detection. The sensitivity of the apparatus is high enough to study weak photoconductors like ZnS. The photoconductivity spectrum of each substance showed a peak at the wavelength corresponding to the energy band gap of the substance. The energy band gaps obtained from the spectra are 2.35 eV for CdS, 1.6 eV for CdSe, 2.7 eVfor ZnSe and 3.6 eV for ZnS, and are in excellent agreement with the values reported in the literature. A photovoltaic cell was made using CdS-Cu2S heterojunction. The V-I characteristic and the short circuit photoconductivity spectrum of this cell were studied. An attempt has been made to automate the experiment using an M6800 D2 microcomputer.