High-Efficiency Thin-Film Cadmium Telluride Photovoltaic Cells; Final Subcontract Report,

Technical Report · Wed Dec 09 04:00:00 EST 1998

OSTI ID:6097492

Compaan, A D; Bohn, R G

This report describes work performed during the past year by The University of Toledo photovoltaics group. Researchers continued to develop rf sputtering for CdS/CdTe thin-film solar cells and to optimize the post-deposition process steps to match the characteristics of the sputtering process. During the fourth phase of the present contract, we focused on determining factors that limit the efficiency in our all-sputtered thin-film CdTe solar cells on soda-lime glass. These issues include controlling CdS/CdTe interdiffusion, understanding the properties of the CdSxTe1-x alloy, optimizing process conditions for CdCl2 treatments, manipulating the influence of ion bombardment during rf sputtering, and understanding the role of copper in quenching photoluminescence and carrier lifetimes in CdTe. To better understand the important CdS/CdTe interdiffusion process, we have continued our collaboration with the University at Buffalo and Brookhaven National Synchrotron Light Source in measurements using grazing-incidence X-rays. Interdiffusion results in the formation of the ternary alloy material CdSxTe1-x at or near the heterojunction, where its properties are critical to the operation of the solar cell. We have placed significant effort on characterizing this alloy, an effort begun in the last phase. A complete set of films spanning the alloy range, prepared by pulsed-laser deposition, has now been characterized by wavelength dispersive X-ray spectroscopy and optical absorption at NREL; by Raman scattering, X-ray diffraction, and electrical measurements in our lab; and by spectroscopic ellipsometry at Brooklyn College. We continued to participate in cooperative activity with the CdTe National Team. We prepared a series of depositions on borosilicate glass substrates having doped SnO2 layers coated with TiO2 (prepared by the University of South Florida and Harvard) and similar substrates having a resistive SnO2 layer on the doped tin oxide (fabricated by Golden Photon). The Golden Photon high-resistivity SnO2 structure yielded excellent cell performance.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE
• OSTI ID: 6097492
• Report Number(s): NRLE/SR-520-25856; ON: DE00009547
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140000* -- Solar Energy
CADMIUM TELLURIDE SOLAR CELLS
COLLISIONS
DIRECT ENERGY CONVERTERS
DOCUMENT TYPES
EFFICIENCY
EQUIPMENT
FILMS
ION COLLISIONS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PROGRESS REPORT
SOLAR CELLS
SOLAR EQUIPMENT
SPUTTERING
THIN FILMS