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Relaxation radiative processes in thin-film electroluminescent structures

Keywords:

M.K. Samokhvalov – Dr.Sc.(Phys.-Math.), Professor, Department «Electronic Instrumentation Design and Technology», Ulyanovsk State Technical University
E-mail: sam@ulstu.ru


Thin-film structures transparent electrode-dielectric-phosphor-dielectric-metal are used in the indicator devices of alternating current means of information display. Electroluminescent indicators occupy a special place among various types of active indicators due to their flat solid-state design, performance, wide range of operating temperatures, high brightness and resolution, durability, resistance to radiation effects, etc. Analysis of the dependence of the radiation brightness on time (brightness waves). it is necessary to study the dynamics of electroluminescence processes in order to establish the basic physical laws of the phenomena and to determine the possibility of using the effects for practical purposes. For the application of thin-film electroluminescent radiation sources in the indicator devices, it is necessary that the brightness increase is fast enough to excite the glow with short pulses, and the attenuation of the radiation was long enough to control the brightness of the pulses with a large duty cycle.
The relaxation of the radiation brightness (brightness waves) in thin-film electroluminescent structures is studied. Based on the model of direct impact excitation of the activator centers in the phosphor, the relations connecting the luminance brightness with the conditions of excitation of radiative structures (the value of the active current in the phosphor layer) are obtained. Use for calculations the resulting equations in a general form based on experimental data can be performed using numerical methods The possibility to calculate the values of the cross section of the shock excitation and the relaxation time of the activators characterizing the interaction processes accelerated by the electric field of the charge carriers with the center of luminescence in the phosphor and emission of photons by excited atoms was shown, using measurements of the waves and brightness of the active current in thin-film structures for particular cases.
Experimental studies of brightness relaxation were carried out for the structures of transparent electrode-dielectric-phosphor-dielectric-metal, consisting of layers sequentially deposited on the glass substrate using thin-film techniques. Zinc sulfide with various activator impurities was used as a phosphor. The values of activator parameters (impact excitation cross sections and constant glow time) for various activators in zinc sulfide films doped with manganese and fluoride terbium, samarium and tullium are determined. The obtained values correspond to the results of measurements of these values by other methods.
The obtained results can be used in the selection of materials and design of thin-film electroluminescent capacitors and devices, as well as to calculate the modes of operation and development of control devices for indicator devices based on them.

References:
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