Photoelectrochemical Behavior of n-Type Porous-Si Electrodes

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Abstract
A prolonged photoanodic operation of n-type Si in aqueous electrolytes was observed with porous-structure Si electrodes. The n-type porous-Si layers (n-PSL) were formed on n-Si substrates (1-2 Ωcm in resistivity) by anodic treatments in an HF solution. The total output charge Q obtainable from a n-PSL photoelectrochemical cell increased in proportion to the n-PSL thickness d. At d = 50 µm, Q reached 12.5 C/cm2; this was four orders of magnitude greater than was obtained from naked n-Si photoanodes. The H2 evolution rate from the Pt counterelectrode was about 60 µmol/2 h at d = 30 µm. The experimental results of the spectral response suggest an increase in the surface state density of the n-PSL surface with increasing d.