Passivation of silicon surfaces by heat treatment in boiled water and its application of solar cells

We report passivation of silicon surfaces by heat treatment in boiled water. 500-μm-thick n- and p-type silicon substrates with bare surfaces were treated in boiled water for 1 h at 97-99°C. High values of the effective minority carrier lifetime were obtained to be 6.3×10^-4 and 4.0×10^-5 s for n- and p-type samples. The recombination velocity was estimated to be 34 and 680 cm/s for n- and p-type samples. Those results indicate a possibility of passivation of silicon surfaces by simple heat treatment in boiled water. Metal-insulator-semiconductor type solar cells were demonstrated with Al and Au metal formation with gaps of 100 and 90 μm for n- and p-type samples to cause an asymmetric internal built-in potential distribution in silicon because of the difference between their work functions. Rectified current voltage and solar cell characteristics were observed. The open-circuit voltage and short-circuit current density were 0.29 V and 11 mA/cm² for n-type sample, and 0.42 V, 5.6 mA/cm² for p-type sample.