FABRICATION OF CADMIUM-SULFIDE - COPPER-SULFIDE THIN FILM SOLAR CELLS BY AN ALL VACUUM DEPOSITED PROCESS AND THEIR RELATED STUDIES

A detailed description of CdS-Cu(,x)S solar cell fabrication facilities and test set up established in the Semiconductor Solid State Electronics Laboratory in the Electrical and Computer Engineering Department of Clarkson College of Technology is presented.;Thin film CdS-Cu(,x)S solar cells were prepared using an all evaporated process called sequential evaporation process. A description of CdS, and Cu(,x)S deposition procedures is given. The characteristics of the solar cells prepared by the sequential evaporation process are presented.;Cells made so far by this method have yielded a short circuit current density of 11 mA/cm('2) and an open circuit voltage of 0.51 V under the illumination of Am1 (100mW/cm('2)). However these maximum values were not seen simultaneously on the same cell. After fabrication, without heat treatment, two types of cells were produced. One type, with a high resistivity (> 20 (OMEGA)-cm) CdS layer exhibited a normal diode characteristic. The other, with a low resistivity (< 1 (OMEGA)-cm) CdS layer had a straight line I-V characteristic suggesting band to band tunneling.;The model proposed by Fahrenbruch and Bube of Stanford University was adopted to explain the current transport mechanisms in the solar cells. The effect of H(,2) heat treatment on cell characteristics is discussed in terms of the barrier theory proposed by te Velde.;An in situ resistance measurement technique which was used to study the CdS and Cu(,x)S films by monitoring their resistances during and after evaporation of the cadmium sulfide and the copper sulfide is described. A simple mathematical procedure was used to calculate the thickness and resistivity of the films. It is possible to consistently reproduce the films which result in high performance solar cells.;Finally the Newton-Raphson method is described which was used to calculate the parameters from the I-V curves of the solar cells and help find the degradation sources by observing the effect of the parameter variations on the performance of the I-V curves.