Luminescent photoelectrochemical cells. 5. multiple emission from tellurium-doped cadmium sulfide photoelectrodes and implications regarding excited-state communication. Technical report
Samples of single-crystal, n-type, 100 ppm Te-doped CdS (CdS:Te) exhibit two emission bands when excited at several ultraband gap wavelengths. One emission band with lambda sub max approximates 510 nm is near the band gap of CdS:Te (approximates 2.4 eV) and is likely edge emission. Its decay time, measured for samples immersed in sulfide solution between 295 and 333 K, is faster than the pulse from the N2-pumped dye laser (approximates 7 nsec) used for 458-nm excitation. The other emissive transition, lambda sub max approximates 600 nm, involves intraband gap states introduced by Te. Intensity-time curves for this band have rise times of less than 10 nsec and generally exhibit nonexponential decay; values of tau sub 1/e are typically 120 + or - 40 and 80 + or - 30 nsec at 295 and 333 K, respectively. When CdS:Te is used as the photoanode in a photoelectrochemical cell employing sulfide electrolyte, both emission bands are quenched in parallel during passage of photocurrent resulting from 457.9- or 476.5-nm Ar ion laser excitation. Parallel quenching is observed at several temperatures for which the excited-state kinetic schemes are demonstrably different: open-circuit emission spectra reveal that both the absolute and relative intensities of the two emission bands are affected by temperature. With increasing temperature (295-333 K) the absolute intensities of both bands decline; a semilog plot of the ratio of 510- to 600-nm intensity vs. T to the -1 is linear with a slope of approximates 0.2 eV, corresponding to the energy gap between the two excited states. The existence of excited-state communication is inferred from the effects of temperature and electrode potential on multiple emission.
- Research Organization:
- Wisconsin Univ., Madison (USA). Dept. of Chemistry
- OSTI ID:
- 5989508
- Report Number(s):
- AD-A-093692
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
ANODES
CADMIUM COMPOUNDS
CADMIUM SULFIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CRYSTAL DOPING
ELECTROCHEMICAL CELLS
ELECTRODES
ELECTROLYTES
EMISSION SPECTRA
ENERGY GAP
ENERGY-LEVEL TRANSITIONS
EQUIPMENT
EXCITATION
IMPLANTS
INORGANIC PHOSPHORS
KINETICS
LASERS
LUMINESCENCE
PHOSPHORS
PHOTOANODES
PHOTOCHEMICAL REACTIONS
PHOTOELECTROCHEMICAL CELLS
PHOTOLUMINESCENCE
QUENCHING
REACTION KINETICS
SOLAR EQUIPMENT
SPECTRA
SULFIDES
SULFUR COMPOUNDS
TELLURIUM COMPOUNDS