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

Abstract Al 2 O 3 has been shown to provide an outstanding passivation quality on p‐type surfaces after annealing at moderate temperatures (∼425 °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 Al 2 O 3 passivation, symmetrical p and p + np + lifetime samples were coated with Al 2 O 3 and exposed to typical firing processes at temperatures between 700 °C and 850 °C. Up to a firing temperature of 825 °C the Al 2 O 3 passivation is shown to be stable on highly boron‐doped surfaces. An emitter saturation current density of ∼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 Al 2 O 3 is an important step for the realization of an industrial n‐type silicon solar cell. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)