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Laser induced defects in laser doped solar cells
Author(s) -
Hameiri Z.,
Puzzer T.,
Mai L.,
Sproul A. B.,
Wenham S. R.
Publication year - 2011
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.1043
Subject(s) - materials science , optoelectronics , substrate (aquarium) , laser , solar cell , doping , common emitter , layer (electronics) , coating , stack (abstract data type) , transmission electron microscopy , silicon , optics , nanotechnology , oceanography , physics , geology , computer science , programming language
Abstract Laser doping offers a promising method to define selective emitters for solar cells. Its main advantage is the localised nature of the laser beam, which allows melting of the surface area without heating the bulk. The ability to perform this process over a dielectric film offers further benefits, such as the possibility of creating self‐aligned metallisation patterns simultaneously with the selective emitter formation. However, laser induced defects, contaminations and discontinuities in the selective emitter can reduce solar cell performance. In this work the influence of different dielectric films on defect formation is investigated. It was found that a thin oxide beneath the SiN x improves the implied open circuit voltage of the solar cells for a wide range of laser output powers. Fewer defects were observed when using this SiO 2 /SiN x stack compared to the standard single SiN x anti‐reflection coating layer. It was also found that the recrystallised silicon layer grows epitaxially according the substrate orientation. No dislocation or stacking faults were observed in deeper areas using transmission electron microscopy, although some defects were observed near the surface. Electron beam induced current images revealed discontinuities in junctions formed with high laser powers. We conclude that micro‐cracks create these discontinuities, which can potentially induce shunts. Finally, laser doped solar cells with a standard SiN x and with a double SiO 2 /SiN x stack layer as anti‐reflection coating were compared. An efficiency of 18.4% on a large area commercial grade p‐type CZ substrate was achieved. Copyright © 2010 John Wiley & Sons, Ltd.