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Impact of metallization techniques on 20 % efficient silicon solar cells

: Kopp, J.; Warta, W.; Aberle, A.G.; Glunz, S.; Knobloch, J.


Institute of Electrical and Electronics Engineers -IEEE-:
22nd IEEE Photovoltaic Specialists Conference '91. Vol.I
New York/N.Y., 1991
ISBN: 0-87942-636-5
Photovoltaic Specialists Conference <22, 1991, Las Vegas/Nev.>
Conference Paper
Fraunhofer ISE ()
high efficiency silicon solar cell; metallisation; metallization; MOS-Messung; Oxiddickenvariation; PCD-Messung

The damage to the Si-SiOsub2 interface by electron- beam in comparison to thermal (i.e. resistive heating) evaporation of Al and Ti is investigated for oxide thicknesses ranging from 14 to 105 nm. C-V and PCD measurements on MOS test structures fabricated on 1 to 100 Omegacm p-type FZ-silicon reveal: (i) severe damage to the interface is caused by e-beam, but not by thermal evaporation, (ii) in terms of midgap interface state densities and PCD time constants the electron-beam damage is removed by a postmetallization anneal in forming gas for all oxide thicknesses, (iii) a photoresist or Al layer of up to 1.6Mym yields no effective shielding. Solar cells with thick passivating oxides (105 nm) gave comparably high efficiencies above 20 % for both metallization techniques. The earlier reported poor passivation quality of thin oxides on solar cell emitters metallized by electron-beam evaporation is possibly due to an increase of the interface state density towards the band egdes.