High-efficiency white organic light emitting devices with three separate phosphorescent emission layers

Abstract

We demonstrate high-efficiency white organic light emitting devices (WOLEDs) employing three adjacent phosphorescent emission layers (3-EMLs). The metal-organic dopants for red, green, and blue emissions are each doped in separate hosts, allowing for separate optimization of the three dopant-host material combinations. This structure distributes the exciton generation region across the three hosts to form a stepped progression of highest occupied and lowest unoccupied molecular orbitals. The 3-EML WOLED has a color rendering index of 81 and peak forward-viewing external quantum (EQE) and power efficiencies (PE) of (16.6±0.8)% and 32±1lm∕W, respectively, corresponding to a total EQE=(28±1)% and a total PE=54±3lm∕W. When an n-doped electron transporting layer is used, the total PE peaks at 64±3lm∕W, and rolls off to 34±2lm∕W at 1000cd∕m2.

Solution-processed multilayer small-molecule light-emitting devices with high-efficiency white-light emission

“…Finally, we fabricated solution-processed multilayer white OLEDs by incorporating green-emitting Ir(ppy) 3 (0.2 wt%) and red-emitting tris(2-phenyl-1-quinoline)iridium(III) (Ir(phq) 3 ) (0.7 wt%) into the blue EML. Although the electroluminescence (EL) spectra of white OLEDs typically depend on current density (in other words, luminance) 4,6,19,[34][35][36][37] , the resulting solution-processed white OLED surprisingly showed no perceived change in the EL spectra under varying current density, as shown in Fig. 6a.…”

“…Such multilayer structures allow for the separation of the charge-injecting, chargetransporting and light-emitting functions to the different layers, thus leading to a marked increase in efficiency and lifetime [1][2][3][4][5] . Although stepwise vacuum evaporation easily achieves the required multilayer structures of small molecules at the expense of high manufacturing cost, it is more challenging in the case of solution processing, because depositing one layer would dissolve the layer beneath it.…”

Full phosphorescent white-light organic light-emitting diodes with improved color stability and efficiency by fine tuning primary emission contributions

“…On the one hand, an efficient white-light PhOLED should maximize its electroluminescence (EL) of all primary color emission, which requires avoiding the triplet-triplet interaction between different color emissive excitons. A stacked multi-layer white-light PhOLED structures with separate primary color emission is a good strategy as reported by Sun YR et al 11 On the other hand, the color of white-light PhOLED is dominated by the EL contribution ratio of primary color excitons. So, a white-light a Author to whom correspondence.…”

“…[1][2][3][4][5][6][7][8][9][10][11] Among them, white-light phosphorescent organic light emitting diodes (PhOLEDs) are very promising owing to their higher efficiency than white-light fluorescent OLEDs. 1,4,[9][10][11] Considerable progresses were made in high efficient white-light PhOLED in the last decades, with a great number of color stable white-light PhOLEDs reported. 12,13 However, it is still difficult to obtain both a very stable color and a high efficiency in the same single white PhOLED.…”

Effect of Doping Profile of Blue Activator on the Emission Characteristics of White Organic Light Emitting Diodes

“…OLED 소자의 발광 효율을 향상시키기 위한 방법 으로 높은 효율을 가지는 물질을 적용하는 방법 이외 에 소자의 구조를 제어하는 방법에 대한 연구가 이루 어지고 있다 [7][8][9][10][11][12][13][14][15][16] …”