Passivation of aluminium-n silicon contacts for solar cells by ultrathin Al2O3 and SiO2 dielectric layers

Abstract

Ultra-thin thermally grown SiO2 and atomic-layer-deposited (ALD) Al2O3 films are trialled as passivating dielectrics for metal-insulator-semiconductor (MIS) type contacts on top of phosphorus diffused regions applicable to high efficiency silicon solar cells. An investigation of the optimum insulator thickness in terms of contact recombination factor J0_cont and contact resistivity ρc is undertaken on 85 Ω/□ and 103 Ω/□ diffusions. An optimum ALD Al2O3 thickness of ∼22 Å produces a J0_cont of ∼300 fAcm-2 whilst maintaining a ρc lower than 1 mΩ cm2 for the 103 Ω/□ diffusion. This has the potential to improve the open-circuit voltage by a maximum 15 mV. The thermally grown SiO2 fails to achiev..