FABRICATION OF CADMIUM TELLURIDE SOLAR CELLS BY CLOSE-SPACED SUBLIMATION (CSS)

Abstract

A decisive factor in large scale utilization of photovoltaic solar cells is its cost and all out efforts are being directed internationally to reduce the same at unprecedented rates. There are very few less developed countries which are able to join this race at the entry level. A break through in this direction was made during his PhD by the PI, based on which research efforts were initiated at the College of EME, Rawalpindi in 1993. These efforts were recognized by Pakistan Science Foundation in 1995 by providing a research grant of Rs 500,000.00. The research has been completed and all the objectives included in the original proposal have been achieved. During this period the research remained focussed on fabrication of thin films for low cost manufacture of solar cells by close-spaced sublimation. This solar cell has three distinct layers of thin films; a tin oxide film under the glass acts as transparent top conducting layer, under it is deposited a layer of cadmium sulphide (CdS) which acts as n-type layer, and under this layer a p-type CdTe layer is deposited through closespaced sublimation (CSS). The process of close-spaced sublimation is carried out in low grade vacuum created by mechanical pumps where the sublimation of material takes place in closed environments on to the glass super strate. This type of system was not available in Pakistan and the same has been designed and fabricated to fabricate solar cells based on this technology. In the proposed research four objectives were specified as shown below, and all of them have been achieved. OBJECTIVE-1. Design and fabricate an experimental setup for deposition of CdTe solar cells by CSS. OBJECTIVE-2. Deposit layer of CdS films by CSS. OBJECTIVE-3. Deposit layers of CdTe films by CSS. OBJECTIVE-4. Fabricate CdTe solar cells by CSS.