THIN FILM SILICON FOR SOLAR CELL APPLICATION GROWN FROM LIQUID PHASE ON METALLURGICAL GRADE SILICON

ABSTRACT: Liquid phase epitaxy was applied to grow roughly 10 µm thick n-type polycrystalline silicon film on p-type metallurgical grade (MG) silicon substrate at 900 ° C in gallium/indium solution. GaAs, dissolved in the melt, served as an arsenic donor source for the as-grown film. The carrier concentration of both the substrate and the as-grown film was 1 × 1018 cm−3 which is too high for practical photovoltaic applications. A post growth exposure to hydrogen plasma lowered the carrier concentration at the p-n junction by an order of magnitude, resulting in functional photovoltaic devices with an open circuit voltage VOC of up to 480 mV. A morphology study, carried out by scanning electron microscope and atomic force microscope, revealed grain size in the range 1 – 3 mm, reflecting the grain size of the substrate. Our result indicates that usable solar-cells may be prepared from unmodified MG silicon without the costly need of recrystallisation for purification