Improved performances in a top-emitting green organic light-emitting device with light magnification

A top-emitting organic light-emitting device (TOLED) with an architecture of Si/SiO₂/Ag (100 nm)/Ag₂O (UV ozone treatment for 30 s)/ 4′,4?-tris(3-methylphenylphenylamino)triphenylamine (45 nm)/4,4′-bis [N-(1-naphthyl-1-)-N-phenyl-amino]-biphenyl (5 nm)/tris-(8-hydroxyquinoline) aluminum (Alq₃):10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-benzo[l]-pyrano[6,7,8-ij]quinolizin-11-one (C545T) (1: 0.5 weight %, 20 nm)/Alq₃ (30 nm)/LiF(1 nm)/Al (0.5 nm)/Ag(30 nm) is designed with a resonance wavelength in the TOLED corresponding to the peak wavelength of C545T. With this enhanced cavity structure, light magnification with a coefficient of ∼ 19 (forward direction) is observed, leading to significantly improved performances with brightness of 80215 cd/m² at 9 V, luminous efficiency of 32.7 cd/A at 6 V, external quantum efficiency of 8.9% at 7.5 V, and low turn-on voltage of 2.5 V.     

Highly efficient red phosphorescent Ir(III) complexes for organic light- emitting diodes based on aryl(6-arylpyridin-3-yl)methanone ligands

A series of phosphorescent Ir(III) complexes 1-4 were synthesized based on aryl(6-arylpyridin-3-yl)methanone ligands, and their photophysical and electroluminescent properties were characterized. Multilayer devices with the configuration, Indium tin oxide/4,4′,4″-tris(N-(naphthalene-2-yl)-N-phenyl-amino)triphenylamine (60 nm)/4,4′-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (20 nm)/Ir(III) complexes doped in N,N′-dicarbazolyl-4,4′-biphenyl (30 nm, 8%)/2,9-dimethyl-4,7-diphenyl-phenathroline (10 nm)/tris(8-hydroxyquinoline)-aluminum (20 nm)/lithium quinolate (2 nm)/ Al (100 nm), were fabricated. Among these, the device employing complex 2 as a dopant exhibited efficient red emission with a maximum luminance, luminous efficiency, power efficiency and quantum efficiency of 16200 cd/m² at 14.0 V, 12.20 cd/A at 20 mA/cm², 4.26 lm/W and 9.26% at 20 mA/cm², respectively, with Commission Internationale de l'Énclairage coordinates of (0.63, 0.37) at 12.0 V.     

Red-phosphorescent OLEDs employing iridium (III) complexes based on 5-benzoyl-2-phenylpyridine derivatives

A series of red-phosphorescent iridium (III) complexes 1-4 based on 5-benzoyl-2-phenylpyridine derivatives was synthesized. Their photophysical and electrophosphorescent properties were investigated. Multilayered OLEDs were fabricated with a device structure ITO/4,4′,4″-tris(N-(naphtalen-2-yl)-N-phenyl-amino)triphenylamine (60 nm)/4,4′-bis(N-naphtylphenylamino)biphenyl (20 nm)/Ir(III) complexes (8%) doped in 4,4′-N,N′-dicarbazolebiphenyl (30 nm)/2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (10 nm)/tris(8-hydroxyquinolinyl)aluminum(III) (20 nm)/Liq (2 nm)/Al (100 nm). All devices exhibited efficient red emissions. Among those, in a device containing iridium complex 1 dopant, the maximum luminance was 14200 cd/m² at 14.0 V. Also, its luminous, power, and quantum efficiency were 10.40 cd/A, 3.44 lm/W and 9.21% at 20 mA/cm², respectively. The peak wavelength of the electroluminescence was 607 nm, with CIE coordinates of (0.615, 0.383) at 12.0 V, and the device also showed a stable color chromaticity with various voltages.     

Synthesis, thermal, photoluminescent, and electroluminescent properties of a novel quaternary Eu(III) complex containing a carbazole hole-transporting functional group

A novel quaternary Eu(III) complex containing a carbazole fragment as hole-transporting functional group was synthesized, and its thermal stability, photoluminescent (PL), electroluminescent (EL) properties were studied. Its glass transition temperature (T _g) was 131 °C and 5% weight loss temperature was 325 °C. In studies of its EL properties, two devices with the Eu(III) complex as red light-emitting materials were fabricated and measured. Device 1: ITO/NPB (40 nm)/Eu(III) complex (30 nm)/Alq₃ (30 nm)/LiF (0.7 nm)/Al (100 nm), NPB was N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine as the hole-transporting layer, Alq₃ was tris(8-hydroxyquinoline) aluminum as the electron-transporting layer. Device 1 gave two emission bands of the Eu(III) complex and Alq₃ with the maximum luminance of 437 cd/m² at 17.34 V, and its turn-on voltage was 10 V. In device 2, an electron-transporting/hole-locking layer of BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 30 nm) was added between the Eu(III) complex and Alq₃ layers, only a sharp red emission band of the Eu(III) complex was given with the maximum luminance of 186 cd/m² at 20.08 V, and its turn-on voltage was 12 V.     

Synthesis and electroluminescent properties of diphenyl benzeneamine derivatives as dopant material

We report the photo- (PL) and electroluminescence (EL) properties of new conjugated compounds based on diphenyl benzeneamine moiety, 4,4′-[1,4-phenylenedi-(1E)-2,1-ethenediyl]bis[N,N-diphenyl-benzenamine](PEDB) and 4,4′-([1,1′-biphenyl]-4,4′-diyldi-2,1-ethenediyl)bis[N,N-diphenyl-benzenamine](BPEDB), as emitting materials and dopant materials. The ITO/m-MTDATA/NPB/DPVBi+BPEDB(1%)/Alq3/LiF/Al device shows blue EL spectrum at 458 nm and high efficiency(5.3 cd/A). PEDB as dopant shows also blue EL spectrum around λmax=463 nm and 4.1 cd/A high efficiency in ITO/m-MTDATA/NPB/DPVBi+ PEDB(1%)/Alq3/LiF/Al device.     

Photo/electroluminescence properties of an europium (III) complex doped in 4,4′-N,N′-dicarbazole-biphenyl matrix

The photoluminescence properties of one europium complex Eu(TFNB)₃Phen (TFNB = 4,4,4-trifluoro-1-(naphthyl)-1,3-butanedione, Phen = 1,10-phenanthroline) doped in a hole-transporting material CBP (4,4′-N,N′-dicarbazole-biphenyl) films were studied. A series of organic light-emitting devices (OLEDs) using Eu(TFNB)₃Phen as the emitter were fabricated with a multilayer structure of indium tin oxide, 250 Ω/square)/TPD (N,N′-diphenyl-N,N′-bis(3-methyllphenyl)-(1,1′-biphenyl)-4,4′-diamine, 50 nm)/Eu(TFNB)₃phen (x): CBP (4,4′-N,N′-dicarbazole-biphenyl, 45 nm)/BCP (2,9-dimethyl-4,7-diphenyl-l,10 phenanthroline, 20 nm)/AlQ (tris(8-hydroxy-quinoline) aluminium, 30 nm)/LiF (1 nm)/Al (100 nm), where x is the weight percentage of Eu(TFNB)₃phen doped in the CBP matrix (1-6%). A red emission at 612 nm with a half bandwidth of 3 nm, characteristic of Eu(III) ion, was observed with all devices. The device with a 3% dopant concentration shows the maximum luminance up to 1169 cd/m² (18 V) and the device with a 5% dopant concentration exhibits a current efficiency of 4.46 cd/A and power efficiency of 2.03 lm/W. The mechanism of the electroluminescence was also discussed.     

Sr/Ag semitransparent cathodes for top emission organic light-emitting devices

We have developed a semitransparent cathode for the top emission organic light-emitting devices using a Sr/Ag double layer prepared by the thermal evaporation technique. The Sr (8-10 nm)/Ag (10 nm) cathode shows the transmittance of 55-76% in the visible spectral region and the sheet resistance of about 12 Ω/□. The underlying Sr layer affects the growing characteristics of Ag layer, resulting in high optical transparency. The bis[2-(2′-benzothienyl)-pyridinato-N,C^3′]iridium(acetylacetonate) doped top emission electro-phosphorescent device with a Sr/Ag semitransparent cathode has been fabricated and studied.     

Study of thermal degradation of organic light emitting device structures by X-ray scattering

We report the process of thermal degradation of organic light emitting devices (OLEDs) having multilayered structure of [LiF/tris-(8-hydroxyquinoline) aluminum(Alq₃)/N,N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPB)/copper phthalocyanine (CuPc)/indium tin oxide (ITO)/SiO₂ on a glass] by synchrotron X-ray scattering. The results show that the thermally induced degradation process of OLED multilayers has undergone several evolutions due to thermal expansion of NPB, intermixing between NPB, Alq₃, and LiF layers, dewetting of NPB on CuPc, and crystallization of NPB and Alq₃ depending on the annealing temperature. The crystallization of NPB appears at 180 °C, much higher temperature than the glass transition temperature (T_g = 96 °C) of NPB. The results are also compared with the findings from the atomic force microscope (AFM) images.     

Light-emitting characteristics of organic light-emitting diodes with the MoOx-doped NPB and C60/LiF layer

The hole ohmic properties of the MoO_x-doped NPB layer have been investigated by analyzing the current density-voltage properties of hole-only devices and by assigning the energy levels of ultraviolet photoemission spectra. The result showed that the performance of organic light-emitting diodes (OLEDs) is markedly improved by optimizing both the thickness and the doping concentration of a hole-injecting layer (HIL) of N, N′-diphenyl-N, N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (NPB) doped with molybdenum oxide (MoO_x) which was inserted between indium tin oxide (ITO) and NPB. For the doping concentration of above 25%, the device composed of a glass/ITO/MoO_x-doped NPB (100 nm)/Al structure showed the excellent hole ohmic property. The investigation of the valence band structure revealed that the p-type doping effects in the HTL layer and the hole concentration increased at the anode interfaces cause the hole-injecting barrier lowering. With both MoO_x-doped NPB as a hole ohmic contact and C₆₀/LiF as an electron ohmic contact, the device, which is composed of glass/ITO/MoO_x-doped NPB (25%, 5 nm)/NPB (63 nm)/Alq₃ (37 nm)/C₆₀ (5 nm)/LiF (1 nm)/Al (100 nm), showed the luminance of about 58,300 cd/m² at the low bias voltage of 7.2 V.     

White top-emitting organic light-emitting diodes using one-emissive layer of the DCJTB doped DPVBi layer

White top-emitting organic light-emitting diodes (TEOLEDs) composed of one doped emissive layer which emits two-wavelength light though the radiative recombination were fabricated. As the emissive layer, 4,4-bis(2,2-diphenylethen-1-yl)biphenyl (DPVBi) was used as the host material and 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) was added as the dopant material. By optimizing the DCJTB concentration (1.2%) and the thickness of the DPVBi layer (30 nm), the intensity ratio of the two wavelengths could be adjusted for balanced white light emission. By using the device composed of glass/Ag (100 nm)/ITO (90 nm)/2-TNATA (60 nm)/NPB (15 nm)/DPVBi:DCJTB (1.2%, 30 nm)/Alq₃ (20 nm)/Li (1.0 nm)/Al (2.0 nm)/Ag (20 nm)/ITO (63 nm)/SiO₂ (42 nm), the Commission Internationale d'Eclairage (CIE) chromaticity coordinate of (0.32, 0.34) close to the ideal white color CIE coordinate could be obtained at 100 cd/m².     

High-efficiency white organic light-emitting devices with a non-doped yellow phosphorescent emissive layer

Highly efficient phosphorescent white organic light-emitting devices (PHWOLEDs) with a simple structure of ITO/TAPC (40 nm)/mCP:FIrpic (20 nm, x wt.%)/bis[2-(4-tertbutylphenyl)benzothiazolato-N,C²′] iridium (acetylacetonate) (tbt)₂Ir(acac) (y nm)/Bphen (30 nm)/Mg:Ag (200 nm) have been developed, by inserting a thin layer of non-doped yellow phosphorescent (tbt)₂Ir(acac) between doped blue emitting layer (EML) and electron transporting layer. By changing the doping concentration of the blue EML and the thickness of the non-doped yellow EML, a PHWOLED comprised of higher blue doping concentration and thinner yellow EML achieves a high current efficiency of 31.7 cd/A and Commission Internationale de l'Eclairage coordinates of (0.33, 0.41) at a luminance of 3000 cd/m² could be observed.     

Electroluminescence of a device based on europium β-diketonate with phosphine oxide complex

Rare earth (RE) ions have spectroscopic characteristics to emit light in narrow lines, which makes RE complexes with organic ligands candidates for full color OLED (Organic Light Emitting Diode) applications. In particular, β-diketone rare earth (RE³⁺) complexes show high fluorescence emission efficiency due to the high absorption coefficient of the β-diketone and energy transfer to the central ion. In this work, the fabrication and the electroluminescent properties of devices containing a double and triple-layer OLED using a new β-diketone complex, [Eu(bmdm)₃(tppo)₂], as transporting and emitting layers are compared and discussed. The double and triple-layer devices based on this complex present the following configurations respectively: device 1: ITO/TPD (40 nm)/[Eu(bmdm)₃(tppo)₂] (40 nm)/Al (150 nm); device 2: ITO/TPD (40 nm)/[Eu(bmdm)₃(tppo)₂] (40 nm)/Alq₃ (20 nm)/Al (150 nm) and device 3: ITO/TPD (40 nm)/bmdm-ligand (40 nm)/Al (150 nm), were TPD is (N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1-biphenil-4,4-diamine) and bmdm is butyl methoxy-dibenzoyl-methane. All the films were deposited by thermal evaporation carried out in a high vacuum system. These devices exhibit high intensity photo- (PL) and electro-luminescent (EL) emission. Electroluminescence spectra show emission from Eu³⁺ ions attributed to the ⁵D₀ to ⁷F_J (J = 0, 1, 2, 3 and 4) transitions with the hypersensitive ⁵D₀ → ⁷F₂ transition (around 612 nm) as the most prominent one. Moreover, a transition from ⁵D₁ to ⁷F₁ is also observed around 538 nm. The OLED light emission was almost linear with the current density. The EL CIE chromaticity coordinates (X = 0.66 and Y = 0.33) show the dominant wavelength, λ_d = 609 nm, and the color gamut achieved by this device is 0.99 in the CIE color space.     

Improvement of color purity in white OLED based on Zn(HPB)2 as blue emitting layer

We synthesized zinc (II) [2-(2-hydroxyphenyl)benzoxazole] (Zn(HPB)₂) as blue emitting materials and evaluated in the organic light emitting diodes (OLEDs). The layer of Zn(HPB)₂ doped with 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) (Zn(HPB)₂:DCJTB) as emitters has been demonstrated. The structure of the device is indium-tin-oxide (ITO)/N,N′-bis-(1-naphthl)-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB, 40 nm)/Zn(HPB)₂/Zn(HPB)₂:DCJTB/Alq₃ (20 nm)/LiF/Al. The thickness of Zn(HPB)₂ layer was 0, 10, 20, 30 nm at the same time the thickness of Zn(HPB)₂:DCJTB layer were 40, 30, 20, 10 nm. When thickness of Zn(HPB)₂ layer was 30 nm and the thickness of Zn(HPB)₂:DCJTB layer was 10 nm, white emission is achieved. The Commission Internationale de l'Eclairage (CIE) coordinates of the white emission are (0.304, 0.332) at an applied voltage of 10.5 V.     

Organic light-emitting diodes with 2-(4-biphenylyl)-5(4-tert-butyl-phenyl)-1,3,4-oxadiazole layer inserted between hole-injecting and hole-transporting layers

Organic light-emitting diodes (OLEDs) were fabricated based on copper phthalocyanine (CuPc) (hole-injecting layer), N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) (hole-transporting layer) and tris(8-hydroxyquinoline) aluminum (Alq₃) (emission and electron-transporting layer). A 2-(4-biphenylyl)-5(4-tert-butyl-phenyl)-1,3,4-oxadiazole (PBD) layer was inserted between CuPc and NPB. The effect of different thickness of PBD layer on the performance of the devices was investigated. The device structure was ITO/CuPc/PBD/NPB/Alq₃/LiF/Al. Optimized PBD thickness was about 1 nm and the electroluminescent (EL) efficiency of the device with 1 nm PBD layer was about 48 percent improvement compared to the device without PBD layer. The inserted PBD layer improved charge carriers balance in the active layer, which resulted in an improved EL efficiency. The performance of devices was also affected by varying the thickness of NPB due to microcavity effect and surface-plasmon loss.     

White organic light-emitting diodes from three emitter layers

Three-wavelength white organic light-emitting diodes (WOLEDs) were fabricated using two doped layers, which were obtained by separating the recombination zones into three emitter layers. A sky blue emission originated from the 4,4′-bis(2,2′-diphenylethen-1-yl)biphenyl (DPVBi) layer. A green emission originated from a tris(8-quinolinolato)aluminum (III) (Alq₃) host doped with a green fluorescent 10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1]benzopyrano [6,7,8-ij]-quinolizin-11-one (C545T) dye. An orange emission was obtained from the N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) host doped with a red fluorescent dye, 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB). A white light resulted from the partial excitations of these three emitter layers by controlling the layer thickness and concentration of the fluorescent dyes in each emissive layer simultaneously. The electroluminescent spectrum of the device was not sensitive to the driving voltage of the device. The white light device showed a maximum luminance of approximately 53,000 cd/m². The external quantum and power efficiency at a luminance of approximately 100 cd/m² were 2.62% and 3.04 lm/W, respectively.     

Organic light-emitting devices based on solution-processible quinolato-complex supramolecules

This paper discusses a new type of supramolecular material tris{5-N-[3-(9H-carbazol-9-yl)propyl]-N-(4-methylphenyl)aminesulfonyl-8-hydroxyquinolato} aluminum(III), Al(SCarq)₃, which we synthesized using three 5-N-[3-(9H-carbazol-9-yl)propyl]-N-(4-methylphenyl)aminesulfonyl-8-hydroxyquinoline as bidentate ligands. The peak photoluminescence in the solid phase appears at 488 nm. In cyclic voltammetric measurement, two oxidation peaks, which were obtained at ?5.6 and ?5.9 eV, correspond to HOMO sites of carbazoyl and aluminum quinolates, respectively. In the investigation of solid morphological thin film, the flat surface was investigated using an atomic force microscope. The root mean square (rms) and mean roughness (R_a) were respectively measured to be 0.427 and 0.343 nm. For the fabrication of organic light-emitting devices (OLEDs) using spin-coating techniques, the turn-on voltage and maximum luminescence of the optimized electroluminescence device, glass/ITO (20 nm)/PEDOT:PSS (75 nm)/Al(SCarq)₃ (85 nm)/BCP (8 nm)/LiF (1 nm)/Al (200 nm), were respectively 9.6 V and 35.0 cd m^?2. Due to the electroplex formation between the carbazole (electron-donor) and the aluminum quinolates (electron-acceptor) moieties under an applied DC bias, the chromaticity of electroluminescence shifted to green-yellow with 1931 CIE_x,y (0.40, 0.47).     

Improving light efficiency of white polymer light emitting diodes by introducing the TPBi exciton protection layer

We fabricated and evaluated the efficient white polymer light emitting diode (WPLED) by introducing TPBi exciton protection layer with ITO/PEDOT:PSS/PFO:MEH-PPV/TPBi/LiF/Al structure. PFO and MEH-PPV were prepared by the spin coating as the light emitting host and guest materials. TPBi was used as exciton protection material. The dependences of the MEH-PPV concentrations into the PFO (PFO:MEH-PPV) on the optical and electrical properties of the WPLEDs were investigated. The effect of the introduction of TPBi layer was studied by means of the property comparison between the samples with and without TPBi layer. The maximum luminance with 1480 cd/m² was obtained at the MEH-PPV concentration of 1.0 wt.% for the ITO/PEDOT:PSS/PFO:MEH-PPV/LiF/Al structure. In addition, the maximum luminance and current efficiency of the WPLED with TPBi layer were 7560 cd/m² at 12 V and 7.8 cd/A at 10 cd/m², respectively. The CIE color coordinates for WPLED with 1.0 wt.% MEH-PPV concentration was found to be (x, y) = (0.36, 0.33), showing pure white color.     

Highly efficient blue OLEDs based on diphenylaminofluorenylstyrenes end-capped with heterocyclic aromatics

In this paper, we have designed four diphenylaminofluorenylstyrene derivatives end-capped with heterocyclic aromatic groups, such as 9-phenylcabazole, 4-dibenzofuran, 2-benzoxazole, 2-quinoxaline, respectively. These materials showed blue to red fluorescence with maximum emission wavelengths of 476–611 nm, respectively, which were dependent on the structural and electronic nature of end-capping groups. To explore the electroluminescent properties of these materials, multilayer OLEDs were fabricated in the following sequence: ITO/DNTPD (40 nm)/NPB (20 nm)/2% doped in MADN (20 nm)/Alq₃ (40 nm)/Liq. (1 nm)/Al. Among those, a device exhibited a highly efficient blue emission with the maximum luminance of 14,480 cd/m² at 9 V, the luminous efficiency of 5.38 cd/A at 20 mA/cm², power efficiency of 2.77 lm/W at 20 mA/cm², and CIE_x,y coordinates of (0.147, 0.152) at 8 V, respectively.     

A novel fluorinated europium ternary complex for highly efficient pure red electroluminescence

A novel fluorine-functionalized europium(III) ternary complex, i.e., Eu(DBM)₃(BFPP), in which DBM was dibenzoylmethane and BFPP 2, 3-bis(4-fluorophenyl)pyrazino[2,3-f] [1,10]phenanthroline, was designed, synthesized and characterized. The complex emits the characteristic red emission of trivalent europium ion due to the ⁵D₀ → ⁷F_j (j = 0–4) transitions under photo excitation with good luminescent quantum efficiency (0.55) and exhibits high thermal stability (387 °C). The organic light-emitting diodes (OLEDs) employing the complex as a dopant emitter with the structures of ITO/TPD (40 nm)/CBP:Eu-complex (30 nm)/Bphen (10 nm)/Alq₃ (20 nm)/LiF (1 nm)/Al (150 nm) were successfully fabricated. The 4 wt.% Eu(DBM)₃(BFPP) doped device exhibited the maximum luminance of 1766 cd/m² and a peak current efficiency of 4.6 cd/A, corresponding to the high external quantum efficiency of 2.27%.     

Efficient red electrophosphorescent organic light-emitting diodes based on the new sensitized heteroleptic tris-cyclometalated Ir(III) complexes

Organic light-emitting device (OLED) was fabricated using the novel red phosphorescent heteroleptic tris-cyclometalated iridium complex, bis(2-phenylpyridine)iridium(III)[2(5′-methylphenyl)-4-diphenylquinoline] [Ir(ppy)₂(dpq-5CH₃)], based on 2-phenylpyridine (ppy) and 2(5′-methylphenyl)-4-diphenylquinoline (dpq-5CH₃) ligand. Generally, the ppy ligand in heteroleptic iridium complexes plays an important role as “sensitizer” in the efficient energy transfer from the host (CBP; 4,4,N,N′-dicarbazolebiphenyl) to the luminescent ligand (dpq-5CH₃). We demonstrated that high efficiency through the “sensitizer” can be obtained, when the T₁ of the emitting ligand is close to T₁ of the sensitizing ligand. The device containing Ir(ppy)₂(dpq-5CH₃) produced red light emission of 614 nm with maximum luminescence efficiency and power efficiency of 8.29 cd/A (at 0.09 mA/cm²) and 5.79 lm/W (at 0.09 mA/cm²), respectively.