DEFECT PASSIVATION IN MULTICRYSTALLINE-SI MATERIALS BY PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION OF SIO2 SIN COATINGS/

It is shown for the first time that plasma-enhanced chemical vapor dep osition (PECVD) passivation which involves low temperature PECVD of ap proximately 100 angstrom SiO2 and approximately600 angstrom SiN follow ed by photoassisted anneal is very effective for both surface and bulk defect passivation in multicrystalline-Si materials. It is found that the effective recombination lifetime increased by a factor of 2-10 de pending upon the multicrystalline material. Some solar cells were fabr icated using a three-layer PECVD coating (100 angstrom SiO2/600 angstr om SiN/950 angstrom SiO2), the bottom two for passivation and the top two for antireflection coating. The bulk and surface passivation effec ts were quantified and decoupled by a combination of internal quantum efficiency measurements and computer modeling. It was found that the P ECVD passivated solar cells increased bulk lifetime from 10 to 20 mus, and decreased the surface recombination velocity from 2x10(5) to 5x10 (4) cm/s. (C) 1994 American Institute of Physics.