SOLAR CELLS IN THIN EPITAXIAL LAYERS ON METALLURGICAL SILICON SUBSTRATES

Publisher Website
Google Scholar
Abstract
Conversion efficiencies of 11.5-12% have been obtained for solar cells with an active layer epitaxially grown on upgraded metallurgical grade silicon substrates made by industry. An epilayer thickness of 30 μm was shown to be sufficient if the substrate doping is much larger than the epilayer doping. Spectral response measurements, fitted to simple models, showed that: • the electron diffusion length reached 120 μm in the epilayer, • a back surface field was efficient in increasing collection efficiency, • Optical path enhancement due to texturisation decreased absorption losses. These results were confirmed by modeling of the short circuit current and open circuit voltage of the cells. Economic viability is discussed. The results can also be used to increase the efficiency of conventional solar cells built on thin wafers (< 150μm).