This report summarizes work performed by the University of South Florida Department of Electrical Engineering under this subcontract. The cadmium telluride (CdTe) portion of this project deals with the development of high-efficiency thin-film CdTe solar cells using fabrication techniques that are suitable for manufacturing environments. The process being developed for semiconductor deposiiton isclose-spaced sublimation (CSS), which has demonstrated high throughput and efficient material utilization. During Phase II, an all-CSS device fabricated on Libbey-Owens-Ford substrate exhibited a 14.3% efficiency. Alternative transparent conducting oxides (TCOs) and window materials being studied under this project include zinc oxide (ZnO) and zinc selenide (ZnSe). The best efficiency obtainedfor a ZnSe/CdTe device was 11.3%. This work also included fabricating CdTe solar cells heat-treated with CdCl2 vapor instead of the typical methanol/CdCl2 wet process, which has produced some encouraging results. The copper indium gallium diselenide (CIGS) portion of the project focused on developing a semiconductor that reliably and reproducibly produced high Jsc values. A key objective wasachieved: the ability to optimize bulk and surface properties independently of each other. Researchers were able to boosst Voc values above 500 mV on 40 mA/m2 base materials and achieve efficiencies of 13%.

This report summarizes work performed by the University of South Florida Department of Electrical Engineering under this subcontract. The Cadmium telluride(CdTe) portion of this project deals with the development of high-efficiency thin-filmed CdTe solar cells using fabrication techniques that are suitable for manufacturing environments.

The main objective of this project is to develop high-efficiency CdTe solar cells based on processing conditions favorable for manufacturing processes. This report presents the results on work performed during the first phase of this project. One of the major issues addressed is the use of soda-lime glass substrates in place of the borosilicate glass often used for laboratory devices; anothertask is the preparation of Cu(In,Ga) Se2 solar cells by selenizing suitable precursor films. Emphasis is placed on processing and how different reaction schemes affect device performance. It was found that different reaction schemes not only change the bulk properties of Cu(In,Ga)Se2, but also its surface properties, which critically affect device performance. Although the objective is tooptimize processing to meet the manufacturing constraints, work has not been limited within these requirements.;

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 tasksinclude 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 our processing is manufacturing-driven, we use an all solid-state, simplifiedtwo-step process that relaxes the level of deposition control required.

The main objective of this project is to develop high-efficiency CdTe solar cells based on processing conditions favorable for manufacturing processes. This report presents the results on work performed during the first phase of this project. One of the major issues addressed is the use of soda-lime glass substrates in place of the borosilicate glass often used for laboratory devices; another task is the preparation of Cu(In,Ga) Se2 solar cells by selenizing suitable precursor films. Emphasis is placed on processing and how different reaction schemes affect device performance. It was found that different reaction schemes not only change the bulk properties of Cu(In,Ga)Se2, but also its surface properties, which critically affect device performance. Although the objective is to optimize processing to meet the manufacturing constraints, work has not been limited within these requirements.