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경과 시간에 따른 청색 형광 OLED의 Impedance 특성
출처
한국표면공학회
발행일
2017-10-31
분야분류
IT소재부품, 해외동향, 전자정보디바이스, LED, IT부품정보, IT부품정보 네트워크, 부품, GreenIT,
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In order to study current-voltage-luminance and impedance characteristics according to elapsed time, a blue fluorescent OLED was fabricated. The current density and luminance gradually decreased in accordance with elapsed time and did not emit light after 480 hours, and the threshold voltage increased as time elapsed. The Cole-Cole plot was a semicircular shape of a very large size at 2 V of the applied voltage below the threshold voltage, and the maximum value of the real number impedance did not change greatly from 9314.5 to 9902.2 Ω as time elapsed. Applied voltages 4, 6, and 8 V above the threshold voltage showed a large change in the real number impedance value at the semicircle end to 9,678.2, 9,826, 9,534 Ω according to the elapsed time from 2,222.5, 183.7, 48.2Ω immediately after fabricating the device. By increasing the applied voltage beyond the threshold voltage just after device fabrication, the energy difference between the device and the organic layer was overcome and the current flowed, the maximum value of the real number impedance sharply decreased. As time passed, current did not flow through the element even at high applied voltage due to degradation of the element, and even when the applied voltage was higher than the threshold voltage, it showed an impedance value such as applied voltage equal to or less than the threshold voltage. As a result, it can be learned that the change in the impedance with elapsed time reflects the characteristics due to the degradation of the OLED and can predict the characteristics and lifetime of the OLED.