• 한국재료학회지
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• 제32권7호
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• pp.320-325
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• 2022

Single OLED and tandem OLED was manufactured to analyze the electroluminescence characteristics of DC driving, AC driving, and full-wave rectification driving. The threshold voltage of OLED was the highest in DC driving, and the lowest in full-wave rectification driving due to an improvement of current injection characteristics. The luminance at a driving voltage lower than 10.5 V (8,534 cd/m²) of single OLED and 20 V (7,377 cd/m²) of a tandem OLED showed that the full-wave rectification drive is higher than that of DC drive. The luminous efficiency of OLED is higher in full-wave rectification driving than in DC driving at low voltage, but decrease at high voltage. The full-wave rectification power source may obtain higher current density, higher luminance, and higher current efficiency than the AC power source. In addition, it was confirmed that the characteristics of AC driving and full-wave rectification driving can be predicted from DC driving characteristics by comparing the measured values and calculated values of AC driving and full-wave rectification driving emission characteristics. From the above results, it can be seen that OLED lighting with improved electroluminescence characteristics compared to DC driving is possible using full-wave rectification driving and tandem OLED.

• 한국정보전자통신기술학회논문지
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• 제15권3호
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• pp.205-210
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• 2022

본 논문은 OLED 구동 박막 트랜지스터의 문턱전압 변동에 의한 AMOLED 디스플레이의 휘도 불균일도를 개선하기 위해 n-채널 박막 트랜지스터만을 사용한 새로운 OLED 화소회로를 제안하였다. 제안한 OLED 화소회로는 6개의 n-채널 박막 트랜지스터와 2개의 커패시터로 구성하였다. 제안한 OLED 화소회로의 동작은 커패시터 초기화 구간, OLED 구동 박막 트랜지스터의 문턱전압을 감지하는 구간, 영상 데이터 전압 기입 구간 및 OLED 발광 구간으로 구성되어 있다. SmartSpice 시뮬레이션 결과, OLED·구동 박막 트랜지스터의 문턱전압이 1.5±0.3 V 변동 시 제안한 OLED 화소회로는 OLED 전류 1 nA에서 최대 전류 오차가 5.18 %이고 OLED 음극 전압이 0.1 V 상승 시 제안한 OLED 화소회로가 기존 OLED 화소회로보다 OLED·전류 변화가 매우 적었다. 그러므로, 기존 OLED 화소회로보다 제안한 화소회로가 문턱전압 변동 및 OLED 음극 전압 상승에 뛰어난 보상 특성을 가진다는 것을 확인하였다.

• 한국표면공학회지
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• 제50권5호
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• pp.398-404
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• 2017

In order to study the AC driving mechanism for OLED lighting, the fluorescent OLEDs were fabricated and the electroluminescent characteristics of the OLEDs by AC forward bias were analyzed. In the case of the driving method of OLED by AC forward bias under the same voltage and the same current density, degradation of luminescent characteristics for elapsed time progressed faster than in the case of the driving method by DC bias. These phenomena were caused by the peak voltage of AC forward bias which is ${\sqrt{2}}$ times higher than the DC voltage. In addition, the degradation of the OLED was accelerated because the AC forward bias had come close to the upper limit of the allowable voltage range even though the peak voltage didn't exceed the allowable range of the OLED. However, the fabricated fluorescent OLED showed little degradation of OLED characteristics due to AC forward bias from 0 V to 6.04 V. Therefore, OLED lighting by AC driving will become commercialized if sufficient luminance is realized at a voltage at which the characteristics of the OLED are not degradation by the AC driving method.

• 한국전기전자재료학회논문지
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• 제27권2호
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• pp.104-109
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• 2014

To operate organic light emitting device (OLED) with alternating current (AC) power source without AC/DC(direct current) converter, we fabricated the fluorescent OLED and measured the emission characteristics with AC and DC. The OLED operated by AC showed higher maximum current efficiency of 8.2 cd/A and maximum power efficiency of 8.3 lm/W. But current efficiency and power efficiency of AC driven OLED showed worse than DC driven OLED at high voltage above 10 V. This result can be explained by the peak voltage of AC was $\sqrt{2}$ times than DC, In case of low driving voltage the emission characteristics were improved by the peak voltage of AC, but in case of high driving voltage the emission efficiencies were decreased by the roll off phenomena. Finally, serial OLED arrays using twelve OLEDs driven by AC 110 V showed average voltage of 9.17 V, voltage uniformity of 99.0%, average luminance of $1,175cd/m^2$, luminance uniformity of 94.4%.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 II
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• pp.919-922
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• 2003

This paper presents a novel low power driving circuit for passive matrix organic lighting emitting diodes (OLED) displays. The proposed driving method for a low power OLED driving circuit which reduce large parasitic capacitance in OLED panel only use current driving method, instead of mixed mode driving method which uses voltage pre-charge technique. The driving circuit is implemented to one chip using 0.35${\mu}{\textrm}{m}$ CMOS process with 18V high voltage devices and it is applicable to 96(R.G.B)X64, 65K color OLED displays for mobile phone application. The maximum switching power dissipation of driving power dissipation is 5.7mW and it is 4% of that of the conventional driving circuit.

• 한국전자통신학회논문지
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• 제9권3호
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• pp.279-284
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• 2014

본 논문에서는 p-채널 저온 다결정 실리콘 박막 트랜지스터의 문턱전압 변동을 보상할 수 있는 새로운 OLED 화소회로를 제안하였다. 제안한 5-TFT OLED 화소회로는 4개의 스위칭 박막 트랜지스터, 1개의 OLED 구동 박막 트랜지스터 및 1개의 정전용량으로 구성되어 있다. 제안한 화소회로의 한 프레임은 초기화 구간, 문턱전압 감지 및 데이터 기입 구간, 데이터 유지 구간 및 발광 구간으로 나누어진다. SmartSpice 시뮬레이션 결과, 구동 트랜지스터의 문턱전압이 ${\pm}0.25V$ 변동 시 최대 OLED 전류의 오차율은 -4.06%이였고 구동 트랜지스터의 문턱전압이 ${\pm}0.50V$ 변동 시 최대 OLED 전류의 오차율은 9.74%였다. 따라서 제안한 5T1C 화소회로는 p-채널 다결정 실리콘 박막 트랜지스터의 문턱전압 변동에 둔감하여 균일한 OLED 전류를 공급함을 확인하였다.

• 한국전기전자재료학회논문지
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• 제22권3호
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• pp.252-256
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• 2009

We have developed low driving voltage white organic light emitting diode with a new electron transport material, triphenylphosphine oxide ($Ph_{3}PO$). The white light emission was realized with a rubrene yellow dopant and blue-emitting DPVBi layer. The new electron transport layer results in a very high current density at low voltage, resulting in a reduction of driving voltage. The device with a new electron transport layer shows a brightness of $1150\;cd/m^2$ at a low driving voltage of 4.3 V.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
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• pp.1108-1111
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• 2007

OLED driving voltage shift can reduce the OLED display lifetime, especially for digitally driven AMOLED. By operating OLED at high frequency, we were able to suppress OLED voltage shift degradation, expecting improved AMOLED lifetime. We describe frequency dependence of voltage shift obtained from bias stress test of OLED.

• 한국전기전자재료학회논문지
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• 제32권1호
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• pp.40-46
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• 2019

To study the frequency response characteristics of alternating-current-driven organic light-emitting diodes (OLEDs), we fabricated blue-fluorescent OLEDs and analyzed their electroluminescent characteristics according to the alternating current voltage and frequency. The luminance-frequency characteristics of alternating-current-driven OLED was similar to that of a low-pass filter, and the luminance of high-voltage OLED decreased at higher frequency than low-voltage OLED. The luminance characteristics of the OLED according to the frequency is due to the capacitive reactance in the OLED, generated during the alternating current driving. The frequency response characteristics of the OLED according to the voltage is due to the decrease in internal resistance of the organic layer. In addition, the negative voltage component of the alternating current did not affect the frequency response of the OLED. Therefore, the electroluminescent characteristics of OLED with an alternating current power of 60 Hz are not influenced by the frequency.

• 한국전자통신학회논문지
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• 제8권2호
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• pp.207-212
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• 2013

본 논문에서는 n-채널 저온 다결정 실리콘 박막 트랜지스터의 문턱전압 변동을 보상할 수 있는 전압 기입 AMOLED 화소회로를 제안하였다. 제안한 6T1C 화소회로는 5개의 스위칭 박막 트랜지스터, 1개의 OLED 구동 박막 트랜지스터 및 1개의 정전용량으로 구성되어 있다. SmartSpice 시뮬레이션 결과, 구동 트랜지스터의 문턱전압이 ${\pm}0.33$ V 변동시 최대 OLED 전류의 오차율은 7.05 %이고 Vdata = 5.75 V에서 OLED 양극 전압 오차율은 0.07 %로 제안한 6T1C 화소회로가 구동 트랜지스터의 문턱전압 변동에도 균일한 OLED 전류를 공급함을 확인하였다.