Heat treatment in 110°C liquid water used for passivating silicon surfaces

Abstract

We report effective passivation of silicon surfaces by heating single crystalline silicon substrates in liquid water at 110 o C for 1 h. High values of photo-induced effective minority carrier lifetime τ eff were obtained ranging from 8.3x10 -4 to 3.1x10 -3 s and from 1.2x10 -4 to 6.0x10 -4 s over the area of 4 inch sized n-and p-type samples, respectively, while values of τ eff of initial bare samples were lower than 1.2x10 -5 s. The heat treatment in liquid water at 110 o C for 1 h resulted in low surface recombination velocities ranging from 7 to 34 cm/s and from 49 to 250 cm/s for those 4 inch sized n-and p-type samples, respectively. The thickness of the passivation layer was estimated to be approximate only 0.7 nm.Metal-insulator-semiconductor type solar cell was demonstrated with Al and Au metal formation on the passivated surface. Rectified current voltage and solar cell characteristics were observed. Open circuit voltage of 0.49 V was obtained under AM 1.5 light illumination at 100 mW/cm 2 .

Passivation of cut edges of crystalline silicon by heat treatment in liquid water

“…We recently developed a heat treatment method in liquid water at temperatures ranging from 90 °C to 110 °C for low-temperature surface passivation. [30][31][32] The formation of a 0.7 nm thick passivation oxide layer on the silicon surfaces was achieved, with an effective minority carrier lifetime τ eff longer than 1 ms. The high τ eff values were maintained for at least 2 months when the samples were kept in air atmosphere at RT.…”