Passivation of silicon surfaces by oxygen radical followed by high pressure H<inf>2</inf>O vapor heat treatments and its application to solar cell fabrication

Abstract

We report passivation on the silicon surfaces by combination of oxygen radical and high pressure H 2 O vapor heat treatment. The top bear surface of 20 Ωcm n-type silicon substrates with the rear surface coated by 100 nm thermally grown SiO 2 layers were treated by oxygen radical generated from oxygen plasma via a metal mesh closing the plasma induced by 13.56 MHz radio frequency induction-coupled remote plasma with mixed gases of O 2 and Ar at 10 sccm, 1.0 Pa and at a power of 100 W. The samples were subsequently annealed with 1.3×10 6 Pa H 2 O vapor heat treatment at 260°C for 3 h. A high effective minority carrier lifetime of 1.1×10 -3 s was achieved in the case of 635 nm light illumination on the top surface in the case of the oxygen radical treatment for 3 min. Metal-insulator-semiconductor-type solar cells were formed by formation Al and Au metal strips with a gap length of 17 μm on the passivated surfaces. When airmass 1.5 at 100 mW/cm 2 were illuminated on the rear surface with 100 nm thermally grown SiO 2 layers, solar cell characteristics were observed by applying voltage between Al and Au electrodes. The open circuit voltage and efficiency were obtained as 0.51 V and 6.4 %.