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Processes for producing low cost, high efficiency silicon solar cells

United States Patent

5,766,964
June 16, 1998
View the Complete Patent at the US Patent & Trademark Office
Processes which utilize rapid thermal processing (RTP) are provided for inexpensively producing high efficiency silicon solar cells. The RTP processes preserve minority carrier bulk lifetime .tau. and permit selective adjustment of the depth of the diffused regions, including emitter and back surface field (bsf), within the silicon substrate. In a first RTP process, an RTP step is utilized to simultaneously diffuse phosphorus and aluminum into the front and back surfaces, respectively, of a silicon substrate. Moreover, an in situ controlled cooling procedure preserves the carrier bulk lifetime .tau. and permits selective adjustment of the depth of the diffused regions. In a second RTP process, both simultaneous diffusion of the phosphorus and aluminum as well as annealing of the front and back contacts are accomplished during the RTP step. In a third RTP process, the RTP step accomplishes simultaneous diffusion of the phosphorus and aluminum, annealing of the contacts, and annealing of a double-layer antireflection/passivation coating SiN/SiO.sub.x. In a fourth RTP process, the process of applying front and back contacts is broken up into two separate respective steps, which enhances the efficiency of the cells, at a slight time expense. In a fifth RTP process, a second RTP step is utilized to fire and adhere the screen printed or evaporated contacts to the structure.
Rohatgi; Ajeet (Marietta, GA), Doshi; Parag (Altanta, GA), Tate; John Keith (Lawrenceville, GA), Mejia; Jose (Atlanta, GA), Chen; Zhizhang (Duluth, GA)
Georgia Tech Research Corporation (Atlanta, GA)
08/ 579,074
December 22, 1995
The U.S. Government has a paid-up license in the invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided by the terms of Contract Nos. E21-H21 and E21-H31 awarded by the U.S. Department of Energy.