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Thermal stability of the Al2O3 passivation on p-type silicon surfaces for solar cell applications

: Benick, J.; Richter, A.; Hermle, M.; Glunz, S.W.


Physica status solidi. Rapid research letters 3 (2009), No.7-8, pp.233-235
ISSN: 1862-6254
ISSN: 1862-6270
Journal Article
Fraunhofer ISE ()

Al2O3 has been shown to provide an outstanding passivation quality on p-type surfaces after annealing at moderate temperatures (similar to 425 degrees C). However, most industrial silicon solar cells are based on printing technologies for metallization, including a high temperature firing step for the contact formation. To investigate the thermal stability of the Al2O3 passivation, symmetrical p and p(+) np(+) lifetime samples were coated with Al2O3 and exposed to typical firing processes at temperatures between 700 degrees C and 850 degrees C. Up to a firing temperature of 825 degrees C the Al2O3 passivation is shown to be stable on highly boron-doped surfaces. An emitter saturation current density of similar to 60 fA/cm(2) could be measured for the p(+) np(+) samples, allowing a maximum open circuit voltage (V-oc) >695 mV. The firing stability of the Al2O3 is an important step for the realization of an industrial n-type silicon solar cell.