The electroluminescence of porous silicon in formic acid and sodium formate solution at positive biases was investigated by luminescence spectrometer. In was discoved that the blue shift for peak wave lengths of electroluminescence occurred when the positive bias was increased. The emitted photon energy depended linearly on the positive biases, the slope of which was in agreement with that of electroluminescence at negatively biased condition. It was shown by scanning probe technique that there was close relation between luminescence properties of porous silicon and its surfac images. It was suggested that the electroluminescence of porous silicon in the solution of formic acid and sodium formate stemmed from the oxidation if Si-H bonds on the surface of porous silicon. The voltage tunable emitting for porous silicon in formic acid - sodium formate solution at positive biases was revealed, which could be explained by the quantum confinement effect.

Key words: SILICON, FORMIC ACID, SODIUM FORMATE, ELECTROLUMINESCENCE, CHEMILUMINESSENCE