Study of different roles phosphorescent material played in different positions of organic light emitting diodes

Phosphorescent materials are crucial to improve the luminescence and efficiency of organic light emitting diodes (OLED), because its internal quantum efficiency can reach 100%. So the studying of optical and electrical properties of phosphorescent materials is propitious for the further development of phosphorescent OLED. Phosphorescent materials were generally doped into different host materials as emitting components, not only played an important role in emitting light but also had a profound influence on carrier transport properties. We studied the optical and electrical properties of the blue 4,4′-bis(2,2-diphenylvinyl)-1,1′-biphenyl (DPVBi)-based devices, adding a common yellow phosphorescent material bis[2-(4-tert-butylphenyl)benzothiazolato-N,C2′] iridium(acetylacetonate) [(t-bt)₂Ir(acac)] in different positions. The results showed (t-bt)₂Ir(acac) has remarkable hole-trapping ability. Especially the ultrathin structure device, compared to the device without (t-bt)₂Ir(acac), had increased the luminance by about 60%, and the efficiency by about 97%. Then introduced thin 4,4′-bis(carbazol-9-yl)biphenyl (CBP) host layer between DPVBi and (t-bt)₂Ir(acac), and got devices with stable white color.     

Theoretical study on the influence of different NˆN ligands on the electronic structures and optoelectronic properties of heteroleptic Iridium(III) complexes

DFT/TDDFT calculations were carried out to investigate the electronic structures, absorption and phosphorescence properties of a series of heteroleptic Ir(III) complexes consisting of two N-heterocyclic carbene ligands and a conjugated bicyclic N,N′-heteroaromatic (N?N) ligand. On the basis of the results reported herein, we attempt to explain the experimental observations according to which complex (mpmi)₂Ir(pybi) (1) [Hmpmi = 1-(4-tolyl)-3-methyl-imidazole; Hpybi = 2-(pyridin-2-yl)-1H-benzo[d]imidazole] emits green light with an extremely high-quantum phosphorescence efficiency (Φ _PL ) of 79.3%, while a relatively lower Φ _PL (only 11%) was measured for (fpmi)₂Ir(tfpypz) (2) [fpmi = 1-(4-fluorophenyl)-3-methylimdazolin-2-ylidene-C, C^2′; tfpypz = 2-(3-(trifluoromethyl)-1H-pyrazol-5-yl)pyridinato] emitting blue light by tuning the N?N ligands. Besides, we also designed (fpmi)₂Ir(pyN3) (3) [pyN3H = 2-(5-(trifluoromethyl)-2H-1,2,4-triazol-3-yl)pyridine] and (fpmi)₂Ir(pyN4) (4) [pyN4H = 2-(1H-tetrazol-5-yl)pyridine] to explore the influence of electron-withdrawing substituents on N?N ligands on the electronic and optical properties of these Ir(III) complexes. The results revealed that electron-withdrawing substituents can stabilise both HOMOs and LUMOs and induce HOMO–LUMO energy gap change. Moreover, the emission properties can be significantly tuned by introducing different N?N ligands. While new insights were gained on structural and electronic properties, the extremely high Φ _PL of 1 was found to be not inherent to spin-orbital coupling effects, but determined by its large transition dipole moment (μ_{S 1}) upon S ₀–S ₁ transition compared with that of 2. On the basis of these results, the designed complexes 3 and 4 are considered to be the promising candidates for blue-emitting phosphorescence materials with higher Φ _PL than the complex 2.     

Density functional theory and time‐dependent density functional theory study on a series of iridium complexes with tetraphenylimidodiphosphinate ligand

A series of heteroleptic cyclometalated Ir(III) complexes for organic light‐emitting diodes (OLEDs) application have been investigated theoretically to explore their electronic structures and spectroscopic properties. The geometries, the electronic structures, the lowest‐lying singlet absorptions and triplet emissions of Ir(dfppy)₂(tpip), Ir(tfmppy)₂(tpip), and theoretically designed models of Ir(ppy)₂(tpip) were investigated with the density functional theory (DFT)‐based approaches, where ppy = 2‐phenylpyridine, dfppy = 4,6‐difluorophenylpyridine, tfmppy = 4‐trifluoromethylphenylpyridine, and tpip = tetraphenylimidodiphosphinate. Their structures in the ground and their excited states have been optimized at the DFT/Becke 3‐parameter Lee Yang Parr (B3LYP)/Los Alamos National Laboratory 2‐double‐z (LANL2DZ) and time‐dependent DFT/B3LYP/LANL2DZ levels, and the lowest absorptions and emissions were evaluated at B3LYP and M062X level of theory, respectively. Furthermore, the energy transfer mechanism together with the advantage of low efficiency roll‐off for these complexes also can be analyzed here. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis, Crystal Structure and Photoluminescence of a Cyclometalated Iridium(III) Coumarin Complex

In this paper a new cyclometalated iridium(III) coumarin complex, Ir(III)bis(3-(2-benzothiazolyl)coumarinato N,C⁴)(acetylacetonate) (Ir(L)₂(acac)), was synthesized and characterized. X-ray crystallography demonstrated that the iridium(III) ion is hexacoordinated by two C atoms and two N atoms from 3-(2-benzothiazolyl)coumarinato ligands and two O atoms from acac ligand, displaying distorted octahedral coordination geometry. The Ir(L)₂(acac) complex has good thermal stability with less than 2 % weight-reduction occurring at 300 °C, and exhibits strong reddish orange emission. The results shown that Ir(L)₂(acac) is useful for fabrication organic light-emitting diodes.     

Hole transport characteristics in phosphorescent dye-doped NPB films by admittance spectroscopy

Admittance spectroscopy is a powerful tool to determine the carrier mobility. The carrier mobility is a significant parameter to understand the behavior or to optimize the organic light-emitting diode or other organic semiconductor devices. Hole transport in phosphorescent dye, bis[2-(9,9-diethyl-9H-fluoren-2-yl)-1-phenyl-1Hbenzoimidazol-N,C3] iridium(acetylacetonate [(fbi)₂Ir(acac)]) doped into N,N-diphenyl-N,N-bis(1-naphthylphenyl)-1,1-biphenyl-4,4-diamine (NPB) films was investigated by admittance spectroscopy. The results show that doped (fbi)₂Ir(acac) molecules behave as hole traps in NPB, and lower the hole mobility. For thicker films(?300 nm), the electric field dependence of hole mobility is as expected positive, i.e., the mobility increases exponentially with the electric field. However, for thinner films (?300 nm), the electric field dependence of hole mobility is negative, i.e., the hole mobility decreases exponentially with the electric field. Physical mechanisms behind the negative field dependence of hole mobility are discussed. In addition, three frequency regions were divided to analyze the behaviors of the capacitance in the hole-only device and the physical mechanism was explained by trap theory and the parasitic capacitance effect.     

White organic light-emitting device with\ both phosphorescent and fluorescent emissive layers

This paper reports the fabrication of novel white organic light-emitting device（WOLED） by using a high efficiency blue fluorescent dye N-（4-（（E）-2-（6-（（E）-4-（diphenylamino）styryl）naphthalen-2-yl）vinyl）phenyl）oN- phenylbenzenamine （N-BDAVBi） and a red phosphoresecent dye bis （1-（phenyl） isoquinoline） iridium （III） acetylanetonate （Ir（piq）2（acac））. The configuration of the device was ITO/PVK：TPD/CBP： N-BDAVBi /CBP/ BALq： Ir（piq）2（acac）/BCP/Alq3/LiF：AL. By adjusting the proportion of the dopants （N-BDAVBi, Ir（piq）2（acac）） in the light-emitting layer, white light with Commission Internationale de l＇Eclairage （CIE） coordinates of （0.35, 0.35） and a maximum luminance of 25350cd/m2 were obtained external quantum and current efficiency of 6.78% and between the two light-emitting layers and using BCP at an applied voltage of 22V. The WOLED exhibits maximum 12cd/A respectively. By placing an undoped spacer CBP layer as hole blocking layer, the colour stabilization slightly changed when the driving voltage increased from 6 to 22 V.     

High performance polymer light-emitting diodes doped with a novel phosphorescent iridium complex

High performance polymer light-emitting diodes (PLEDs) based on a phosphor of noble metal complex bis(1,2-dipheny1-1H-benzoimidazole) iridium (acetylacetonate) [(pbi)₂Ir(acac)] doped in poly(N-vinylcarbazole) (PVK) host with various concentration were demonstrated. The photoluminescence (PL) and electroluminescence (EL) spectra of the PLEDs exhibited an emission intensity decrease of PVK and a gradually enhanced feature of (pbi)₂Ir(acac) with increased doping concentration. The device with a 5 wt% (pbi)₂Ir(acac) doped PVK system showed a high power efficiency of 3.84 lm/W and a luminance of 26,006 cd/m². The results indicated that both energy transfer and charge trapping have a significant influence on the performance of PLEDs. The devices have a broadened EL spectrum of full-width at half-maximum (FWHM) more than 100 nm, which can be realized for WOLEDs.     

铱金属配合物磷光材料掺杂聚合物体系的电致发光特性

通过对一种新型贵金属铱的配合物磷光材料(pbi)₂Ir(acac)与咔唑共聚物进行物理掺杂, 制备了结构为indium-tin oxide(ITO)/poly(N-vinylcarbazole)(PVK): (pbi)₂Ir(acac)(x)/2,9-dimethyl-4,7-diphenyl-1,10-phenan throline(BCP)(20nm)/8-Hydroxyquinoline aluminum(Alq₃)(10nm)/Mg:Ag的聚合物电致磷光器件,研究了磷光聚合物掺杂体系在低掺杂浓度时(0.1%和0.5%(质量百分数,全文同))的光致发光(PL)和电致发光(EL)特性. 结果表明, 该掺杂体系的PL光谱和EL光谱中均同时存在主体材料PVK与磷光客体(pbi)₂Ir(acac)的发光光谱, 但主客体的发射强度不同,推测该掺杂体系在电致发光条件下, 同时存在主体材料到客体的不完全的能量传递和载流子直接俘获过程. 磷光掺杂浓度为0.1%的器件在19V电压下实现了白光发射, 色坐标为(0.32, 0.38), 掺杂浓度为0.5%的器件在20.6V电压下的最大发光亮度为11827 cd·m^-2, 而在13.4V电压下的最大流明效率为4.13 cd·A^-1. 关键词： 有机电致发光器件 铱配合物磷光 聚合物掺杂     

DFT/TDDFT investigation of the electronic structures and optoelectronic properties of phosphorescent iridium (III) complexes with non-conjugated cyclometalated carbene ligands

This work investigates the electronic structures and spectroscopic properties of several cyclometalated iridium carbene complexes possessing at least one functionalized methylene moiety, (dfpmb)(dfbmb)Ir(mptz) (2), (dfbmb)₂Ir(mptz) (3), and (dfbmb)₂Ir(mpmtz) (4) (dfpmbH =1-difluorophenyl-3-methyl-benzimidazoline-2-ylidene; dfbmbH?=?1-(2,4-difluorobenzyl)-3-(methylbenzimidazolium; mptzH?=?4-methyl-2-(5-(trifluoromethyl)-2H-1,2,4-triazol-3-yl)pyridine); mpmtzH?=?4-methyl-2-(3-methylene-5-(trifluoromethyl)- 2H-1,2,4-triazole-3-yl)pyridine) on the basis of their prototype (dfpmb)₂Ir(mptz) (1) via DFT and TDDFT methods. A careful examination of results shows: (1) the patterns of the occupied orbitals for 1–4 are almost the same, with the HOMO being an admixture of the Ir atom and benzyl part, whereas the LUMO is predominately delocalized over the ancillary chelate mptz or mpmtz; (2) complexes 1–3, and especially 4, all exhibit blue emission with maximum wavelengths at 506, 495, 486, and 478?nm, respectively; (3) complex 4 with the highest (relative) component of ³MLCT can be reasonably expected to have a higher radiative transition rate constant (k_r ) among 1–4. From the highest absorption peaks, eventually, the molar extinction coefficient discrepancy between experiment and calculations might be tentatively attributable to the synergism of the intrinsic imperfection of the PCM model and the simplification of chemical computations.     

基于CBP:BCzVB:Btp2Ir(acac)体系的白色有机电致发光器件色度飘移研究

以苯乙烯类化合物BCzVB为蓝色荧光染料,以铱配合物Btp_2Ir(acac)为红色磷光染料,共掺杂到CBP基质中作为发光层,制备了白色有机电致发光器件,研究了该体系发光色度漂移的原因。器件在掺杂CBP:6?zVB: 0．2%Btp_2Ir(acac),在．驱动电流从4～200 mA/cm~2变化范围内,发光色坐标从(0．340,0．273)飘移到(0．308, 0．273),色坐标轻微蓝移。对器件发光光谱和亮度-电流密度曲线等分析表明:器件色度的轻微蓝移是由于CBP基质向Btp_2Ir(acac)掺杂剂完全的能量传递、荧光染料BCzVB向磷光染料Btp_2Ir(acac)不完全的能量传递等内在物理过程和磷光染料Btp_2Ir(acac)自身发光饱和等特性共同决定的。     

Electroluminescence of organic light-emitting diodes consisting of an undoped (pbi)2Ir(acac) phosphorescent layer

The electroluminescence (EL) characteristics of phosphorescent organic light-emitting diodes (OLEDs) with an undoped bis(1,2-dipheny1-1H-benzoimidazole) iridium (acetylacetonate) [(pbi)₂Ir(acac)] emissive layer (EML) of various film thicknesses were studied. The results showed that the intensity of green light emission decreased rapidly with the increasing thickness of (pbi)₂Ir(acac), which was relevant to the triplet excimer emission. It suggested that the concentration quenching of monomer emission in the undoped (pbi)₂Ir(acac) film was mainly due to the formation of triplet excimer and partly due to the triplet-triplet annihilation (TTA) and triplet-polaron annihilation (TPA). A green OLED with a maximum luminance of 26,531 cd/m², a current efficiency of 36.2 cd/A, and a power efficiency of 32.4 lm/W was obtained, when the triplet excimer emission was eliminated. Moreover, the white OLED with low efficiency roll-off was realized due to the broadened recombination zone and reduced quenching effects in the EML when no electron blocking layer was employed.     

Synthesis and characterization of blue phosphorescent cyclometalated Ir(III) complexes containing 2-(imidazol-2-yl)pyridine as ancillary ligand

Four new blue phosphorescent iridium complexes containing 2-(fluoro substituted phenyl)pyridine as the cyclometalated ligands and 2-(imidazol-2-yl)pyridine as an ancillary ligand have been synthesized and characterized. The complexes have the general structure (C^N)₂Ir(pym), where C^N are cyclometalating ligands (e.g., 2-(2,4-difluorophenyl)pyridine (24f₂ppyH), 2-(3,4-difluorophenyl)pyridine (34f₂ppyH), 2-(3,5-difluorophenyl)pyridine (35f₂ppyH), and 2-(3,4,5-trifluorophenyl)pyridine (345f₃ppyH)), pym is 2-(imidazol-2-yl)pyridine (pymH). The absorption, emission, and cyclic voltammetry of the complexes were systematically investigated. The (46f₂ppy)₂Ir(pym) has been characterized using X-ray crystallography and the electronic ground state calculated using B3LYP density functional theory. The highest occupied molecular orbital (HOMO) consists of a mixture of pym ligand (83.7%) and Ir orbitals (12.1%), while the lowest occupied molecular orbital (LUMO) is mostly on f₂ppy ligands (93.4%). By replacing the ancillary ligand pic with pym can finely tune emission of the iridium complexes, showing blue luminescence at a wavelength of 467-491 nm at room temperature in CH₂Cl₂.     

同时掺杂磷光和荧光染料的白色有机电致发光器件性能研究

以磷光染料Ir(piq)₂(acac)作为发光掺杂剂,掺入空穴传输性主体材料NPB中得到红色发光层,荧光材料TBP掺入到主体CBP中作为蓝色发光层,制备了结构为ITO/NPB/NPB：Ir(piq)₂(acac)/CBP/CBP：TBPe/BCP/ALq/Mg：Ag的双发光层白色有机电致发光器件.其中ALq₃、未掺杂的NPB和CBP及BCP层分别作为电子传输层、空穴传输层和激子阻挡层.实验中通过调节发光层厚度及Ir(piq)_{2关键词： 磷光 激子阻挡层 有机电致发光}     

Synthesis and photophysics of a new deep red soluble phosphorescent iridium(III) complex based on chlorine-methyl-substituted 2,4 diphenyl quinoline

A new iridium complex with a chlorine-methyl-substituted 2,4 diphenyl quinoline, (Cl-MDPQ) ligand has been synthesized. The synthesized iridium metal complex, Ir(Cl-MDPQ)₂(acac) where Cl-MDPQ=chlorine-methyl substituted, 2,4 diphenyl quinoline, acac=acetyl acetone is characterized by employing different techniques such as mass spectrometry, ¹H NMR, DTA/TGA, XRD, and FTIR. The molecular structures of Cl-MDPQ and Ir(Cl-MDPQ)₂(acac) complexes are confirmed by the FTIR spectra. Strong singlet metal-to-ligand charge-transfer (¹MLCT) and triplet metal-to-ligand charge-transfer (³MLCT) absorption peaks at 353 and 437 nm in tetrahydrofuran (THF) are reported in the synthesized complex, respectively. A deep red emitting Ir(Cl-MDPQ)₂(acac) complex at 662 nm is promising for flexible organic devices.     

Study on triplet exciton diffusion length of mCP in phosphorescent organic light-emitting devices using electroluminescent spectra

Electroluminescent (EL) spectra was employed to probe the triplet exciton diffusion length (L_T) of a commonly used host material of N,N′-dicarbazolyl-3,5-benzene (mCP) in phosphorescent organic light-emitting devices (OLEDs). By varying the film thickness of bis [2-(4-tertbutylphenyl) benzothiazolato-N,C²], iridium (acetylacetonate) [(t-bt)₂Ir(acac)] phosphor doped layer within 30 nm thick mCP layer, a series of devices were fabricated to investigate the EL characteristics. The results showed that with the increasing doped layer thickness (d), both (t-bt)₂Ir(acac) emission peaks at 562 nm and mCP emission centered at 403 nm were observed. Moreover, the relationship between mCP EL intensity and d was detected. The L_T was induced by an abrupt decrease in variation of mCP EL intensity when d is increased from 10 to 15 nm, and the reason to cause this phenomenon was investigated. The L_T of mCP approximately to 15 nm was perfectly consistent to the result of 16±1 nm, which was calculated by the traditional steady-state diffusion model.     

Ir配合物染料调节有机发光二极管发光特性

为了研究有机发光二极管(OLED)中发光特性与材料能带结构的关系,把不同的Ir配合物染料掺杂到结构相同的OLED器件中。OLED结构为ITO/NPB/CBP∶染料/TPBi/Mg∶Ag/Ag,染料分别为Ir(MDQ)2(acac)、Ir(ppy)3和Firpic。实验表明,这3种染料对应的掺杂器件分别发红光、绿光和蓝光。3个器件的阈值电压基本一致((6为了研究有机发光二极管(OLED)中发光特性与材料能带结构的关系,把不同的Ir配合物染料掺杂到结构相同的OLED器件中。OLED结构为ITO/NPB/CBP:染料/TPBi/Mg:Ag/Ag,染料分别为Ir(MDQ)₂(acac)、Ir(ppy)₃和Firpic。实验表明,这3种染料对应的掺杂器件分别发红光、绿光和蓝光。3个器件的阈值电压基本一致((6±0.1) V),但是,在100 cd/m²亮度下,绿光器件外量子效率最高(7.64%),蓝光器件外量子效率(5.65%)与绿光相近,红光器件外量子效率最低(2.75%)。分析认为,由于染料的掺杂浓度低,器件结构和载流子传输特性变化小,因而掺杂对阈值电压影响小;CBP与掺杂染料间存在能量转移,红色染料能级差小,非辐射跃迁几率大,发光效率最低;相比于绿光,蓝色染料能级差大,跃迁几率小,因此发光效率比绿光低。实验还发现,染料的发光波长与其能级差相比有红移现象,分析认为,这是由激发态能量振动弛豫和系间窜越过程形成的。     

基于7-（9H-carbazol-9-yl）-N,N-diphenyl-9, 9’-spirobi[fluoren]-2-amine主体材料的高效红色电致磷光器件

研究了基于新型骨架7-（9H-carbazol-9-yl）-N,N-diphenyl-9,9’-spirobi[fluoren]-2-amine（CzFA）双极性主体材料的红色电致磷光器件的光电特性。研究结果表明：将红色磷光染料iridium（Ⅲ）bis[2-methyldibenzo-（f,h）quinoxaline]（acetylacetonate）（Ir（MDQ）₂（acac））掺杂到CzFA主体材料中,以其制备的电致发光器件具有优良的特性,最大电流效率为27.8 cd/A,最大功率效率为21.8 lm/W,最大功率效率几乎是先前报道的主体材料为CBP器件（13.7 lm/W）的1.6倍。这种咔唑-螺二芴-二胺基团所组成的双极性主体材料对于提升磷光器件的性能起到了重要的作用。     

高亮度下具有较高效率的绿色和蓝绿色有机电致发光器件的制备和性能研究(英文)

以铱配合物Ir(tfmppy)2(tpip)(1,tfmppy=4-三氟甲基苯基吡啶,tpip=四苯基膦酰胺)和Ir(dfp-py)2(tpip)(2,dfppy=4,6-二氟苯基吡啶)为发光中心分别制备了绿色和蓝绿色有机电致发光器件ITO/TAPC(1,1-bis[4-[N,N-di(p-tolyl)amino]phenyl]cyclohexane,60 nm)/Ir(Ⅲ)complex(x%,质量分数)∶Sim-CP(3,5-bis(9-carbazolyl)tetraphenylsilane,40 nm)/TPBi(2,2’,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole,60 nm)/LiF(1 nm)/Al(100 nm)。配合物Ir(tfmppy)2(tpip)掺杂质量分数为6%时,以其为发光中心的绿色器件在5 930 cd/m2亮度下的最大电流效率为47.10 cd/A,CIE色坐标为(0.28,0.65),在16.4V驱动电压下的最大发光亮度为38 674 cd/m2。配合物Ir(dfppy)2(tpip)掺杂质量分数为10%时,以其为发光中心的蓝绿色器件在3 175 cd/m2亮度下的最大电流效率为14.80 cd/A,色坐标为(0.15,0.50),在11.8 V驱动电压下的最大发光亮度为25 985 cd/m2。     

Organic‐inorganic hybrids based on phenanthrene‐functionalized gold nanoparticles for OLEDs

The electroluminescence intensity of the phenanthrene‐functionalized gold nanoparticles, PMPT‐Au nanoparticles/CPB: Ir(PIA)₂ (acac) film, was increased by 4.9 times compared with control device, CPB: Ir(PIA)₂ (acac) due to coupling between the excitons of emissive layer and localized surface plasmonic resonance of PMPT‐Au NPs. The maximum luminous efficiencies of devices II to IV with PMPT‐Au NPs were 39.2 cd A^?1 (11.8 V), 40.1 cd A^?1 (10.5 V), and 43.1 cd A^?1 (9.0 V), respectively. The increment of current efficiency with PMPT‐Au NP coated devices was strongly related to the energy transfer between the radiated light generated from CBP: Ir(PIA)₂ (acac) emissive layer and localized surface plasmonic resonance excited by PMPT‐Au NP layer.     

Efficient red organic light-emitting diode sensitized by a phosphorescent Ir compound

The efficiencies of red organic light-emitting diode (OLED) using tris-(8-hydroxy-quinoline)aluminum (Alq₃) as host and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as dopant were greatly increased by adding a small amount (0.3 wt%) of Ir compound, iridium(III) bis(3-(2-benzothiazolyl)-7-(diethylamino)-2H-1-benzopyran-2-onato-N′,C⁴) (acetyl acetonate) (Ir(C6)₂(acac)), as a sensitizer. The device has a sandwiched structure of indium tin oxide (ITO)/4,4′,4″-tris(N-(2-naphthyl)-N-phenyl-amino)triphenylamine (T-NATA) (40 nm)/N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′ diamine (NPB) (40 nm)/Alq₃:DCJTB (0.7 wt%):Ir(C6)₂(acac) (0.3 wt%) (40 nm)/Alq₃ (40 nm)/LiF (1 nm)/Al (120 nm). It can be seen that the current efficiencies of this device remained almost (13.8±1) cd/A from 0.1 to 20,000 cd/m² and the Commission International d’Eclairage (CIE) coordinates at (0.60, 0.37) in the range of wide brightness. The significant improvement was attributed to the sensitization effect of the doped Ir(C6)₂(acac), thus the energy of singlet and triplet excitons is simultaneously transferred to the DCJTB.