Implementation of Low Cost Semi Crystalline Silicon Solar Cells

Summary

This project is related to the introduction of semicrystalline (polycrystal with basaltic structure) silicon wafers into the low cost process of manufacturing photovoltaic cells implemented by France-Photon since 1980 at Angoulême.

The aim of the research into define which modifications are to be brought to the standard process in order to maximize the photovoltaic efficiency of polycristalline cells at a minimum cost.

Our investigations have already concerned,for différent materials:

• 1) Correlations between crystal defects (dislocations, punctual defects, precipitates) and photovoltaic performances.

• 2) Slicingwafers from parallelipedic ingots.

• 3) Chemical etching optimization

• 4) Diffusion profiles

• 5) Front metallization with electroless Nickel plating

• 6) Transfert, conveyance, handling and mechanical stability

• 7) Tolerance to the hot spot problem

• 8) Economic considerations

It appears clearly that semicrystalline material is economically ready to replace single crystal in 1983 although some fondamental problems are not well understood within the grains and grain boundaries and therefore are not well controlled at the manufacturing level, leading to a larger statistical dispersion on wafers and cells than for single crystalline materials.

Best cells are obtained with the new HEM material of Crystal System followed by Semix of Solorex and then Silso of Wacker.

Concerning the dispersion, Silso appears as the more industrial product, followed by Semix and then by HEM which is probably produced in small quantities.