Polarization effects in the luminescence of cadmium selenide electrodes
Polarization properties of the emission from single-crystal, n-type CdSe samples have been examined. When excited with several ultraband gap wavelengths, a plates of n-CdSe (wurtzite structure) exhibit polarized photoluminescence (PL) spectra consistent with the reported electronic structure of the solid. The spectra consist of two bands near the band gap energy (∼1.7 eV) assignable to transitions between the conduction band and a split valence band having its two highest energy band edges separated by ∼0.022 eV; the lower energy band is preferentially polarized with E ⊥ c, while the other band displays no polarization preference. Time-resolved PL data, obtained with 620-nm excitation from a N2-pulsed dye laser, were independent of polarization. Intensity-time curves yielded a decay time (τ1/e) of ∼20 ns for both bands, providing evidence that the two emissive excited states are in thermal equilibrium. Emissive properties of n-CdSe, a-plate electrodes were also consistent with thermal equilibration. Polarized electroluminescence (EL) spectra, obtained by using the solid as a dark cathode in aqueous peroxydisulfate electrolyte, closely resemble their PL counterparts, demonstrating attainment of similar excited-state populations in the two experiments. And when the semiconductor is used as the photoanode of a photoelectrochemical cell employing diselenide electrolyte, the two PL bands resulting from 514.5- or 632.8-nm excitation are quenched in parallel by the electric field present in the semiconductor.
Streckert, H. H., H. Van Ryswyk, R. N. Biagioni, and A. B. Ellis. Polarization effects in the luminescence of cadmium selenide electrodes. Technical report. No. AD-A-133951/4. Wisconsin Univ., Madison (USA). Dept. of Chemistry, 1983.
Journal of Physical Chemistry