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Electrochemiluminescence from porous silicon in formic acid liquid‐junction cells

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5 Author(s)
Green, Will H. ; Department of Chemistry, University of California, San Diego, La Jolla, California 92093‐0358 ; Lee, Eric J. ; Lauerhaas, Jeffrey M. ; Bitner, Theodore W.
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Visible light emission from porous silicon can be stimulated by applying a positive bias to a formic acid/sodium formate liquid junction cell. The emission lasts for 45 min at +2.75 V applied potential (≪5 mA/cm2, power conversion efficiency ≳10-2%) and is reliably generated from n‐ or p‐type porous silicon. An applied voltage as low as 1.3 V is capable of generating the red (720 nm) emission, indicating that current‐induced chemical reactions aid in the generation of charge carriers. A mechanism involving oxidation of formic acid followed by electron injection from a CO2- radical is proposed. Infrared spectra of the porous silicon surface taken after anodization show formation of a stable silyl‐ester species that is thought to be responsible for the increase in radiative recombination efficiency through passivation of surface defects. © 1995 American Institute of Physics.

Published in:

Applied Physics Letters  (Volume:67 ,  Issue: 10 )