DEPOSITION PROCESSES FOR THIN FILM SOLAR CELLS

Angus A. Rockett

The Coordinated Science Laboratory and the Department of Materials Science and engineering. University of Illinois, 1101 West Springfield Avenue, Urbana, Illinois 61801

Phone:217-333-0417, Fax:217-244-1631. E-mail:arockett@staff.uiuc.edu

Long term production of electrical energy will have to rely on renewable sources. Currently common renewable sources of power from water and plant material can be shown to be incapable of producing sufficient energy to meet the needs of a modern society. Solar electric (solar cell) power generation by contrast can produce adequate amounts of power using relatively small land areas. This paper reviews deposition processes used for producing thin film solar cells and potentially scaling up to very large area production. The presentation will focus primarily on the most promising long-term candidate for very large areas CulnSe2 based devices. These solar cells involve sputter deposition of very large areas of metals, particularly Mo, Cu(In1-xGax)Se2 semiconductor alloys by one of a number of methods, and deposition of transparent conducting oxides such as ZnO. Significant issues include epitaxial growth by sputtering combined with evaporation, modification of point-defect solubility, process controls, deposition on large areas and at lower temperatures, and stress control and adhesion in the Mo contact layers. The current status of production of large-area thin films of these materials is described and prospects for further scale-up is considered.