Simulation Study on the Effect of the Emitter Orientation and Photonic Crystals on the Outcoupling Efficiency of Organic Light-Emitting Diodes

Abstract

Combined optical simulation of the ray-tracing technique and the finite difference time domain method was used to investigate the effect of the emitter orientation and the photonic crystal layer on the outcoupling efficiency (OCE) of bottom-emission type organic light emitting diodes (OLEDs). The OLED with a horizontal emitter exhibited an opposite interference effect to that of one with a vertical emitter, which suggested that the OCE would be very sensitive to the emitter orientation at a fixed emitter-cathode distance. The OLED with a horizontal emitter exhibited much larger OCE than that with a vertical emitter did, which was due to the substantial difference in the radiation pattern along with the different coupling with the surface plasmon excitation. The OCE with a horizontal emitter was increased by approximately 1.3 times by inserting a photonic crystal layer between the indium tin oxide layer and the glass substrate. The present study suggested that appropriate control of the emitter orientation and its combination to other outcoupling structures could be used to enhance the OCE of OLEDs substantially.

Emitter Orientation as a Key Parameter in Organic Light-Emitting Diodes

“…An overview of the respective theories and advances using such strategies can be found in the review papers of Brütting et al [86] or Gather and Reineke [87], respectively, but is not discussed here in detail. Furthermore, it should be noted that molecular orientation is crucial for almost all applications based on organic semiconductors, as this feature strongly influences not only the light emission of organic dyes but also the light propagation in stratified media due to birefringence [88][89][90][91] as well as their electrical properties due to orientation-dependent charge carrier transport and injection [92][93][94][95][96][97][98][99][100][101][102][103]. Moreover, light absorption and charge collection in organic solar cells are strongly influenced by molecular orientation of the active materials as well [104][105][106][107][108][109][110][111][112][113][114].…”

Polymer Dispersed Liquid Crystal Imprinted by Microlens Array for Enhanced Outcoupling Efficiency of Organic Light Emitting Diode

“…Consequently, only about 20% of the light is emitted externally, leading to low efficiency [ 5 , 6 , 7 ]. To combat this, numerous studies aim to enhance the external light extraction efficiency of OLED devices to improve power efficiency and extend their lifespan [ 8 , 9 ]. Light extraction technologies primarily focus on minimizing light loss by reducing the refractive index mismatch within the OLED, thereby lessening total internal reflection [ 10 , 11 ].…”

Effects of a Dielectric Multilayer Mirror on the Lighting Efficiency of Organic Light-Emitting Diodes Studied by Optical Simulation

“…순수하게 기하광학적 고려만을 하게 되면 발생한 빛의 20% 미만이 에어 모드로 빠져나가는 것으로 계산된다 [3] . 그 동안 많은 연구자들에 의해 OCE를 향상시키기 위한 다양한 광학 구조가 제안되어 왔는데, 마이 크로렌즈 혹은 확산층을 활용해 기판모드를 추출하는 방법 [5][6][7][8][9][10][11][12] , 도파관 모드로 갇히는 빛을 빼내기 위해 OLED의 내부 구조를 다양하게 변형시키는 접근 방법 [13][14][15][16][17][18][19][20] , 플라스몬 손실 을 줄이거나 [21] 다양한 접근법들을 동시에 적용하는 하이브 리드 방법 [22,23] , 발광층 내 발광자의 방향을 조절하는 방법 [24][25][26][27][28][29][30][31] 등이 시도되어 왔다.…”