Orange Organic Light-emitting Diodes Research Articles

Solution-processed orange organic light-emitting diodes based on phosphorescent iridium(III) complexes with coumarin 6 as the main ligand

Four ionic orange phosphorescent iridium(III) complexes (Ir1, Ir2, Ir3, Ir4) were successfully synthesized using coumarin 6 as the cyclometalated ligand and 2,2′-bipyridine (bpy) derivatives with different number and position of methyl groups as the auxiliary ligand. The effects of substituents in the auxiliary ligands on their properties were systematically investigated. These four complexes exhibited orange emission at wavelengths of 590, 588, 587, and 586 nm, respectively, with excellent solubility and remarkable photophysical properties in different solvents. Furthermore, they were further applied in the organic light-emitting diodes (OLEDs) based on solution method. The maximum luminance of the devices based on Ir1/Ir2/Ir3/Ir4 reached 1907.0/932.6/760.8/519.3 cd/m2, with corresponding maximum current efficiency (CE), power efficiency (PE), and external quantum efficiency (EQE) values of 1.56/1.71/1.97/1.52 cd/A, 0.33/0.32/0.35/0.27 lm/W, and 0.77/0.82/0.90/0.72 %, respectively. Although there is room for improvement in the performance of OLEDs, this strategy inspires us to modulate the novel photoluminescent and electroluminescent properties of iridium(III) complexes through rational modifications of their ancillary ligands.

Efficient orange organic light-emitting diodes employing a central aniline bridged multiresonant thermally activated delayed fluorescence emitter

We report a narrowband orange multiresonant thermally activated delayed fluorescence (MR-TADF) emitter and it use in high-efficiency organic light-emitting diodes.

Electron-Rich Twistacene-Modified Arylboron Donor-Acceptor Systems: Synthesis, Photophysics, and Electroluminescence with Hot Exciton Response.

A series of twistacene-functionalized donor (D)-π-acceptor (A) derivatives (2-5) have been designed and synthesized, in which twistacene can be regarded as a promising platform for electron-rich systems for fluorescence emitters. The connecting modes and various acceptors are also examined to investigate the effect of structural changes on the photophysical, electrochemical, and thermal properties. The strong electron-withdrawing capability of the arylboron-modified benzonitrile unit can effectively separate the HOMO and LUMO energy levels of 4/5, which is beneficial for the formation of thermally activated delayed fluorescence (TADF) molecules. Cyan and orange organic light-emitting diodes based on 4 and 5 exhibit promising electroluminescence with a maximum brightness of 7643 cd m-2 for device-4 and 14871 cd m-2 for device-5.

Low Energy-Consumption Inverted Orange Organic Light-Emitting Diodes with Reduced Efficiency Roll-Off

Inverted organic light-emitting diodes (IOLEDs) have a bottom cathode, making them convenient to integrate with the preferred n-type active matrix OLED driving technologies. Furthermore, inverted OLEDs show much better air-stability compared with conventional OLEDs, due to the very reactive and sensitive of alkali doped electron injection layer (EIL) towards ambient oxygen and moisture. For inverted OLEDs, the bottleneck to limit their efficiency and stability is the interface at cathode/EIL and light emitting layer (EML)/charge transporting layer. In this paper, we have investigated the effect of different electron/hole transporting layers on the turn-on voltage, efficiency roll-off and power consumption of inverted orange OLEDs. We found that the device exhibits extremely-low efficiency roll-off and a significant lifetime improvement.

Effect of end group functionalisation of small molecules featuring the fluorene–thiophene–benzothiadiazole motif as emitters in solution-processed red and orange organic light-emitting diodes

A series of red fluorescent materials (compounds1–4), which each contain the symmetric fluorene–thiophene–BT–thiophene–fluorene core, is presented along with their performance in solution-processed OLED devices.

Orange electrophosphorescence based on bis(3,5-dimethylphenyl)pyridine iridium (III) complexes for non-halogenated solution processable phosphorescent organic light-emitting diodes

Two heteroleptic iridium complexes, (dmppy)2Ir(tmd) and (dmppy)2Ir(acac), which consist of phenylpyridin (ppy) as main ligand with dimethyl substituents on both the phenyl ring and the pyridine ring, and heptanedione (tmd) and acetyl acetonate (acac) as ancillary ligands were synthesized and characterized regarding their suitability as orange organic light-emitting diodes (OLEDs). The photoluminescence (PL) of (dmppy)2Ir(tmd) and (dmppy)2Ir(acac) produced orange emissions with maximum emission peaks at 577 and 570 nm, respectively. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital energy (LUMO) levels of (dmppy)2Ir(tmd) and (dmppy)2Ir(acac) were −5.03/-2.83 and −5.02/-2.77 eV, respectively. An optimized non-halogenated solution-processed (dmppy)2Ir(tmd) device showed a high current efficiency of 52.7 cd/A and exhibits an efficiency of 89% when compared to a vacuum-deposited device that showed 66.7 cd/A at 1000 cd/m2.

Solution-processable highly efficient deep-red and orange organic light-emitting diodes based on multi-functional Ir(iii) complexes

Linking the hole transporting/electron transporting functional moieties to the Ir(iii) complex is a key strategy to improve performance of PhOLEDs.

High efficiency and non-color-changing orange organic light emitting diodes with red and green emitting layers

We report a high performance orange organic light-emitting diode (OLED) where red and green phosphorescent dyes are doped in an exciplex forming co-host as separate red and green emitting layers (EMLs). The OLED shows a maximum external quantum efficiency (EQE) of 22.8%, a low roll-off of efficiency with an EQE of 19.6% at 10,000cd/m2, and good orange color with a CIE coordinate of (0.442, 0.529) and no color change from 1000 to 10,000cd/m2. The exciplex forming co-host system distributes the recombination zone all over the EMLs and reduces the triplet exciton quenching processes.

Orange phosphorescent organic light-emitting diodes with high operational stability

In this article we report on the performances of phosphorescent orange organic light-emitting diodes (OLEDs) having a high operational stability. The fabricated devices all consist of a “hybrid” structure, where the hole-injection layer was processed from solution, while the rest of the organic materials were deposited by vacuum thermal evaporation. A device stack having an emissive layer comprising a carbazole-based host TCzMe doped with the orange phosphor tris(2-phenylquinoline)iridium(III) [Ir(2-phq)3] shows improved efficiencies compared to a the same device with the standard N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine (NPB) as host material. External quantum efficiency (EQE) up to 7.4% and a power efficiency of 16lm/W were demonstrated using TCzMe. Most importantly, the operational stability of the device was largely improved, resulting in extrapolated values reaching lifetimes well above 100,000h at initial luminance of 1000Cd/m2.

Highly Efficient Orange and White Organic Light‐Emitting Diodes Based on New Orange Iridium Complexes

Highly efficient, orange organic light-emitting diodes (OLEDs) fabricated from newly synthesized iridium complexes show a maximum luminance efficiency of 76 cd A−1 and a peak power efficiency of 45 lm W−1. The white OLEDs containing the orange iridium and traditional blue iridium phosphors exhibit extraordinarily high efficiencies and a peak external quantum efficiency of 26%. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Highly efficient orange organic light-emitting diodes using a novel iridium complex with imide group-containing ligands

We report the synthesis and device characterization of a novel iridium complex using a phenylpyridine derivative containing an imide functional group as a bis-cyclometallized ligand ((impy)2Ir(acac)) for orange organic light-emitting diodes (OLEDs). The photoluminescence of the dopant emits orange light with the main peak of 560 nm and a shoulder of 595 nm. The OLEDs made with the synthesized dopant also produce intense orange electroluminescence at 568–572 nm wavelengths depending on the device geometry. Very high peak external quantum efficiencies of 13.8–14.4%, peak power efficiencies of 29.2–32.7 lm/W, and low operation voltages of 5.3–5.4 V at 1000 cd/m2 have been demonstrated for the orange OLEDs.

A Multifunctional Iridium‐Carbazolyl Orange Phosphor for High‐Performance Two‐Element WOLED Exploiting Exciton‐Managed Fluorescence/Phosphorescence

AbstractBy attaching a bulky, inductively electron‐withdrawing trifluoromethyl (CF3) group on the pyridyl ring of the rigid 2‐[3‐ (N‐phenylcarbazolyl)]pyridine cyclometalated ligand, we successfully synthesized a new heteroleptic orange‐emitting phosphorescent iridium(III) complex [Ir(L1)2(acac)] 1 (HL1 = 5‐trifluoromethyl‐2‐[3‐(N‐phenylcarbazolyl)]pyridine, Hacac = acetylacetone) in good yield. The structural and electronic properties of 1 were examined by X‐ray crystallography and time‐dependent DFT calculations. The influence of CF3 substituents on the optical, electrochemical and electroluminescence (EL) properties of 1 were studied. We note that incorporation of the carbazolyl unit facilitates the hole‐transporting ability of the complex, and more importantly, attachment of CF3 group provides an access to a highly efficient electrophosphor for the fabrication of orange phosphorescent organic light‐emitting diodes (OLEDs) with outstanding device performance. These orange OLEDs can produce a maximum current efficiency of ∼40 cd A−1, corresponding to an external quantum efficiency of ∼12% ph/el (photons per electron) and a power efficiency of ∼24 lm W−1. Remarkably, high‐performance simple two‐element white OLEDs (WOLEDs) with excellent color stability can be fabricated using an orange triplet‐harvesting emitter 1 in conjunction with a blue singlet‐harvesting emitter. By using such a new system where the host singlet is resonant with the blue fluorophore singlet state and the host triplet is resonant with the orange phosphor triplet level, this white light‐emitting structure can achieve peak EL efficiencies of 26.6 cd A−1 and 13.5 lm W−1 that are generally superior to other two‐element all‐fluorophore or all‐phosphor OLED counterparts in terms of both color stability and emission efficiency.

P‐177: Characterization of Orange OLED Stack for Bidirectional Active‐Matrix OLED Microdisplays

AbstractHighly efficient, low‐voltage organic light emitting diodes (OLEDs) are well suitable for the integration into a CMOS‐process.An orange emitting phosphorescent OLED‐stack with doped charge transport layers was prepared on different types of CMOS substrates. First OLED deposition was done on a single diode 6″‐Wafer substrate and afterwards on a micro structured two metal layer CMOS test substrate without active transistor area.The different test substrates were measured and compared with respect to their performance (current, luminance, voltage, luminance dependence on viewing angle, optical outcoupling etc.)For bidirectional microdisplay applications the dynamic characteristics of the OLED stack are also of interest. Therefore the charge and discharge behaviour and the switch on and switch off delay time of voltage apply to luminance output are measured and summarised in a simple model.

Orange and red organic light-emitting devices using aluminum tris(5-hydroxyquinoxaline)

Energy transfer in dye-doped organic light-emitting diodes (OLEDs) often occurs by Förster energy transfer processes. In many cases this energy transfer process can be very efficient, leading to fairly large Förster radii. We have recently shown that saturated red emission can be achieved by doping tetraphenylporphine (TPP) into aluminum tris(8-hydroxyquinolate) (Alq 3) in an ITO/TPD/Alq 3/Mg-Ag device (TPD = N,N′-diphenyl- N,N′-bis(3-methylphenyl)-1,1′biphenyl-4,4′ diamine; ITO = indium-tin oxide). Predominant red emission is observed even at very low doping levels, as expected for the large Förster radius for TPP in Alq 3 (33 Å). In order to increase the degree of overlap between the dopant absorption for red fluorescent dyes and the host emission we prepared a strongly red-shifted analog of Alq 3, i.e. aluminum tris(8-hydroxyquinoxalate) (Alx 3). The photoluminescent efficiency for Alx 3 is significantly lower than that of Alq 3, leading to a significant decrease in the electroluminescent quantum yield for Alx 3-based OLEDs relative to Alq 3-based devices. We have examined the doping of several dyes into Alx 3, giving red and orange OLEDs.