Cadmium sulfide-copper sulfide: heterojunction cell research. Quarterly Progress report-1, September 1, 1978-December 1, 1978

The CdS/Cu/sub 2/S cell development effort has now shifted to the planar junction cell. It has been shown that this junction gives a higher open circuit voltage than that achieved with the highly textured cell structure. Optical measurements have shown that applying a two-layer anti-reflection coating to the planar cell does not achieve the high photon economy shown by the textured structure. Total reflectance measurements have revealed that this is due to the lack of light trapping in the planar structure. Modified cell designs are now being developed with the planar junction necessary for high open circuit voltage while achieving the necessary light trapping. Work on the (CdZn)S/Cu/sub 2/S cell has revealed that cell performance is extremely sensitive to the method of Cu/sub 2/S production. Appropriate structural studies have been initiated to identify the underlying reasons. Theoretical analysis and modeling of the current flow in the Cu/sub 2/S layer has shown that the conventional one-dimensional analysis can lead to significant errors in interpreting the effects of sheet resistance. A rigorous two-dimensional current analysis is being conducted. The importance of the changes in absorption coefficient of the Cu/sub 2/S stoichiometry has been identified and the relation between stoichiometry, resistivity and absorption coefficient derived. On the basis of a review of the encapsulation task in the large scale silicon array program it has been determined that inorganic glasses are probably the only viable encapsulant for a CdS/Cu/sub 2/S cell.