Hea. Elgamel, HIGH-EFFICIENCY POLYCRYSTALLINE SILICON SOLAR-CELLS USING LOW-TEMPERATURE PECVD PROCESS, I.E.E.E. transactions on electron devices, 45(10), 1998, pp. 2131-2137
Conventionally directionally solidified (DS) and silicon him (SF) poly
crystalline silicon solar cells are fabricated using gettering and low
temperature plasma enhanced chemical vapor deposition (PECVD) passiva
tion. Thin layer (similar to 10 nm) of PECVD SiO2 is used to passivate
the emitter of the solar cell, while direct hydrogen rf plasma and PE
CVD silicon nitride (Si3N4) are implemented to provide emitter and bul
k passivation, It is found in this work that hydrogen rf plasma can si
gnificantly improve the solar cell blue and long wavelength responses
when it is performed through a thin layer of PECVD Si3N4. High efficie
ncy DS and SF polycrystalline silicon solar cells have been achieved u
sing a simple solar cell process with uniform emitter, Al/POCl3 getter
ing, hydrogen rf plasma/PECVD Si3N4 and PECVD SiO2 passivation. On the
other hand, a comprehensive experimental study of the characteristics
of the PECVD Si3N4 layer and its role in improving the efficiency of
polycrystalline silicon solar cells is carried out in this paper. For
the polycrystalline silicon used in this investigation, it is found th
at the PECVD Si3N4 layer doesn't provide a sufficient cap for the out
diffusion of hydrogen at temperatures higher than 500 degrees C. Low t
emperature (less than or equal to 400 degrees C) annealing of the PECV
D Si3N4 provides efficient hydrogen bulk passivation, while higher tem
perature annealing relaxes the deposition induced stress and improves
mainly the short wavelength (blue) response of the solar cells.