The main tasks of the cadmium telluride portion of this project include the development of simplified processing for fabricating high-efficiency CdTe solar cells, studies on the long-term stability of CdTe devices, and the development of alternative transparent conducting oxides, window layers, and back contacts. The second portion of this project focused on CIGS solar cells. The main tasks include the development of a manufacturable process for CIGS devices and the development of high-band-gap alloys for use in tandem cell structures. Additional objectives include development of improved junction formation processing and contributing to the overall understanding of these materials and devices. Because the processing is manufacturing-driven, the authors use an all solid-state, simplified two-step process that relaxes the level of deposition control required.

This project addresses most of the key CdTe technology areas, with focus on improving the manufacturability and long-term stability of this technology. The activities over this 3-year period include developing simplified processing, studying novel front and back contacts, and improving long-term stability. This report describes work carried out during the last year of the project. The solar cells discussed below are fabricated by various deposition technologies that include chemical vapor deposition, chemical-bath deposition, close-spaced sublimation, and rf-sputtering. The devices are routinely evaluated using standard solar cell analytical techniques such as dark and light current-voltage, spectral response, and capacitance-voltage measurements.