This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. '1 Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessar=ly con-m stltute or imp!y its endorsement, recommendation, or favoring by the United States government or any agency thereof. The wews and opinions oi authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. mn

Fluorosilicic acid is a viable low-cost source of silicon for use in non-aqueous solvents for the electrodeposition of thin silicon layers on continuous plastic film. The acid is converted to an organic salt and purified by extraction. Sealed plastic electrolytic cells purged with N2 gas preserve <10ppm of O2 and H2O during deposition. An unsubmerged liquid jet provides for deposition rates suitable for large-scale production. Plastic film 125mm in width was used as a continuous web for production-scale demonstration. Monolithic crystalline cells with amorphous top cells demonstrated conversion efficiencies as high as 17%. Issues of continuous deposition and process control require further refinement in order to demonstrate consistent web efficiency.

PV markets a g r e a t e r d i s t r i b u t i o n of t h e f a c t o r y output can be u t i l i z e d . Plans f o r such a f a c t o r y and economics a r e given.

A b s t r a c t Thin s e m i c r y s t a l l i n e s i l i c o n s o l a r c e l l s made from a D i r e c t -C a s t method w i t h p a s si v a t e d g r a i n s were a p p l i e d w i t h a back s u r f a c e f i e l d f o r v o l t a g e enhancement. The mold c o a t i n g was m o d i f i e d i n o r d e r t o impr o v e r e l e a s e of very t h i n w a f e r s ( .15mm) from t h e mold. With a s u r f a c e f i n i s h o f 410 microns very t h i n w a f e r s c o u l d be e a s i l y removed from t h e mold w i t h o u t b r e a k a g e and a l s o improved mold c o a t i n g l o n g e y i t y . I NTEO DUC T I ON R e c e n t work w i t h D i r e c t -2 a s t s i l i c o n s o l a r c e l l s h a s shown t h a t e f f i c i e n c i e s comparable t o s i n g l e c r y s t a l c e l l s a r e p o s s i b l e ( 1 ) . S i l c a s t w a f e r s have been made i n t h e t h i c k n e s s r a n g e of 0.15-0.2mm i n o r d e r t o o b t a i n t h e b e n e f i t o f a back s u r f a c e f i e l d ( B S F ) . I n o r d e r ' c t o c a s t w a f e r s t o a t h i c k n e s s o f 0.115-0.2" and minimize w a f e r b r e a k a g e i n rernoval from t h e mold, t h e mold c o a t i n g r e q u i r e d improvement and a r e d u c t i o n i n t h e s u r f a c e f i n i s h . With very t h i n w a f e r s t h e proforma c o s t s f o r f i n i s h e d module a r e e s t i m a t e d a t l e s s t h a n $ l / w a t t w i t h i n t h e n e x t few y e a r s . 5XPER I MENTA L S i l c a s t s e m i c r y s t a l l i n e s i l i c o n w a f e r s a r e produced by a r a p i d s o l i d i f i c a t i o n p m c e s s i n a h i g h p u r i t y g r a p h i % e mold t h a t i s c o a t e d w i t h a m a t e r i a l t h a t w i l l n o t r e a d i l y wet w i t h t h e m o l t e n s i l i c o n . The mold c o a t i n g i s a p p l i e d by a t h e r m a l s p r a y p r o c e s s t h a t r e s u l t s i n a s i l j c o n OxYnltride c o a t i n g w i t h a s u r f a c e f i n i s h of 20-30microns.The mold c o a t i n g s u r f a c e w i l l r e a d i l y r e l e a s e w a f e r s i n t h e t h i c k n e s s r a n g e o f 0.3-0.4". I n t h e f i r s t s e t of e x p e r i m e n t s t h e s p r a y p r o c e s s was m o d i f i e d i n o r d e r t o r e d u c e t h e a s -d e p o s i t e d mold c o a t i n g . A s e r i e s of molds were c o a t e d w i t h v a r y i n g s u r f a c e f i n i s h e s and w a f e r s were c a s t i n o r d e r t o d e t e r m i n e e a s e o f r e l e a s e from t h e mold. The s u r f a c e f i n i s h v a r i e d from 10-30microns and w a f e r s w i t h a t h i a k n e s s r a n g e of 0.15-0.4" were c a s t i n o r d e r t o d e t e r m i n e optimum s u r f a c e f i n i s h f o r a r o u t i n e p r o d u c t i o n o p e r h t i o n . I n a second s e t of e x p e r i m e n t s , t h e t h i n w a f e r s o b t a i n e d f r o m ' t h e mold r e d t h r o u g h t h e s e l a y e r s . \ l a c k e r s l i c e d w a f e r s were c h e m i c a l l y t h i n n e d and c o -p r o c e s s e d w i t h t h e...

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