Transferred Charge in the Active Layer and EL Device Characteristics of TFEL Cells

Abstract

The relationship between transferred charge in the active layer of a thin-film electroluminescent (TFEL) cell and EL device characteristics has been investigated electrically. Making use of a charge density-voltage characteristic measuring system based on a Sawyer-Tower circuit, a general formula for the input power density was found to be given by twice the product of the frequency, the threshold voltage of the active layer, and the transferred-charge density. From this formula, the luminous efficiency could be estimated, once the dependence of the luminance upon the frequency and the transferred charge density was found. At a frequency smaller than the inverse of twice the luminous decay time, e.g. 500 Hz in the ZnS:Mn case, the luminance was found to be proportional to the product of frequency and transferred charge density. Hence, the luminous efficiency becomes constant with a value 2–2.5 times larger than that for 5 or 1 kHz drive conditions.

Effect of halohydrocarbon solvents on the dielectric performance of a polymer film and its application to inorganic electroluminescent devices

“…5. The E p value can be expressed by this equation, E p ¼ ε i V tot /(ε i d p þ ε p d i ), where ε i (ε p ) is the dielectric constant of a dielectric (phosphor) layer, V tot is an applied voltage to the EL device, and d i (d p ) is a thickness of the dielectric (phosphor) layer [7,14,15]. E p was gradually increased with increasing of the dielectric constant of a dielectric layer.…”

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“…The operating voltage of ELD fabricated using a size-selected GaNO layer is also 6 times lower than that in the case of the overall-deposited layer. The results are consisted with the EL intensity dependence on the applied electric field [10].…”

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