THE OBJECTIVE OF THIS WORK IS THE DESIGNING OF A ELECTROLYTIC PROCESS FOR THE PRODUCTION OF SOLAR GRADE AMORPHOUS SILICON, BOTH IN ORGANIC SOLVENTS AND MOLTEN SALTS, IN THE FORM OF A THIN LAYER ON A CONDUCTIVE SUBSTRATE, SUITABLE FOR THE DIRECT MANUFACTURING OF SOLAR CELLS.
The design of a electrolytic process for the production of solar grade amorphous silicon, for the direct manufacturing of solar cells, was investigated. Tests were conducted in nonaqueous solvents, in acetic acid and in tetraethylorthosilicate. We have produced thin layers but, in other electrolytes, deposits were not observed. The results of this prefeasibility research show clearly the possibility of obtaining silicon in baths containing sodium fluoride, potassium fluoride and potassium silicon fluoride (K2SiF6) at temperatures between 750 C and 800 C without the use of lithium salts.
The work comprised these phases:
bibliographic research, including papers published in the literature, patents and industrial reports;
design and construction of laboratory equipment used for electrolytic tests;
purification of raw materials and solvents;
silicon electrodepositon tests;
elaboration of collected data.
We divided the research and development work into 2 areas;
silicon electrodeposition in organic solvents;
silicon electrowinning in molten salts.
THE WORK IS COMPOSED OF THREE PHASES:
1) BIBLIOGRAPHIC RESEARCH, EXTENDING IT TO THE PAPERS PUBLISHED IN THE LITERATURE, PATENTS AND INDUSTRIAL REPORTS.
2. DESIGN AND CONSTRUCTION OF LABORATORY EQUIPMENTS USED FOR ELECTROLYTIC TESTS.
3) PURIFICATION OF RAW MATERIALS AND SOLVENTS.
4) SILICON ELECTRODEPOSITION TESTS.
5) ELABORATION OF COLLECTED DATA.
WE HAVE DIVIDED THE R&D WORK IN TWO MAIN FIELDS:
- SILICON ELECTRODEPOSITION IN ORGANIC SOLVENTS.
- SILICON ELECTROWINNING IN MOLTEN SALTS.
TESTS HAVE BEEN CONDUCTED IN NON-AQUEOUS SOLVENTS: IN ACETIC ACID AND TETRAETHYLORTHOSILICATE WE HAVE PRODUCED THIN LAYERS, IN OTHER ELECTROLYTES DEPOSITS WERE NOT OBSERVED.
THE CELL FOR SILICON ELECTROWINNING IN MOLTEN SALTS HAS BEEN DESIGNED AND IS NOW IN CONSTRUCTION.
OUR PARTNER EXTRAMET IS RUNNING ELECTRODEPOSITION TESTS IN MOLTEN SALTS USING A CELL OF ITS DESIGN.