Luminescent Properties of Semiconductor Photoelectrodes.
WISCONSIN UNIV-MADISON DEPT OF CHEMISTRY
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The use of luminescent, n-type 5-1000-ppm CdSTe and 10 ppm-CdSAg polycrystalline photoelectrodes as probes of recombination in photo-electrochemical cells is reported. Except for intensity, the emission spectra lambda sub max, 600-700 nm are insensitive to the presence of S2-Sn2- electrolyte and to the excitation wavelengths and electrode potentials employed. With ultraband gap irradiation lambda less than or 500 nm and aqueous S2-Sn2- or Te2-Te22- electrolytes, optical energy is converted to electricity at 0.1-5 efficiency and to luminescence at 0.01-1.0 efficiency the effects of surface preparation and grain boundaries in determining efficiency and discussed. Increasingly negative bias applied to CdSTe and CdSAg photoanodes increases emission intensity by 15-100 while the photocurrent simultaneously declines to zero. Band gap edge 514.5-nm excitation yields smaller photocurrents and larger but much less potential dependent emission intensity. These results are consistent with the band bending model presently used to described photoelectrochemical phenomena. Author
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