Yellow Phosphorescent Organic Light-emitting Diodes Research Articles

Efficient Solution-Processed Blue and Yellow Phosphorescent Organic Light-emitting Diodes Using Binary Blend Hosts

The appropriate hosts of emitting layers (EMLs) play an important role in determining the overall performance of solution-processed phosphorescent organic light emitting diodes (PhOLEDs). We have investigated the effect of three species of host molecules, 1,3-bis(carbazol-9-yl)benzene (mCP), 10-(4-(5,5dimethylbenzofuro[3,2-c]acridin-13(5H)-yl)phenyl)-10-phenylanthracen-9(10H)-one (DpAn-5BzAc) and poly(9-vinylcarbazole) (PVK), on the performance of solution-processed blue and yellow PhOLEDs. We have found that compared to the widely used single-host EMLs, the devices using the binary blend of mCP: DpAn5BzAc as hosts, can achieve more efficient optoelectrical characteristics. The maximum current efficiencies of 11.84 and 16.61 have been realized for blue and yellow OLEDs, respectively. The superior electroluminescence performance for binary blend host-based PhOLEDs was attributed to the enhanced charge carrier balance and multi-component miscibility, which has a dramatic influence on the morphology of the emissive layer. These results demonstrate the great potential of the multi-hosts in solution-processed organic optoelectronic devices. The development of complementary colour OLEDs with blue and yellow can provide a simple approach to fabricate solution-processed white PhOLEDs.

High efficiency and low operating voltage yellow phosphorescent organic light-emitting diodes with a simple doping-free structure.

Yellow phosphorescent organic light-emitting diodes (PhOLEDs) with high efficiency and a low operating voltage were reported through using a simple doping-free structure. The structure of the PhOLEDs was ITO/C60/MoO3/mCP/PO-01-TB/PO-T2T/Liq/Al. The np-type C60/MoO3 heterojunction acted as hole injection layer, and the ultrathin PO-01-TB layer (0.1 nm) was inserted at the interface between mCP and PO-T2T to serve as yellow phosphorescent emitter. Detailed investigation suggested that the complete energy transfer occurred from the mCP/PO-T2T interfacial exciplex to yellow PO-01-TB. Furthermore, the np-type C60/MoO3 heterojunction could supply more free charge carriers, giving rise to further enhanced PhOLED efficiency. By adjusting the thickness of the C60/MoO3 heterojunction, a yellow PhOLED with a power efficiency of 71.6 lm W−1 was demonstrated with an extremely low operating voltage of 3.79 V at 1000 cd m−2.

High Performance Yellow Phosphorescent Organic Light-Emitting Diodes Based on an Efficient Carriers Regulating Structure with Iridium Complex as Electron Manager

High Performance Yellow Phosphorescent Organic Light-Emitting Diodes Based on an Efficient Carriers Regulating Structure with Iridium Complex as Electron Manager

Phthalonitrile based charge transfer type host for yellow phosphorescent organic light-emitting diodes

An phthalonitrile based 3,3''-di(9H-carbazol-9-yl)-[1,1':2′,1''-terphenyl]-4′,5′-dicarbonitrile (IPNCz) was explored as a charge transfer type host of a yellow emitting bis(4-phenyl-thieno[3,2-c]pyridinato-C2,N)(acetylacetonato)iridium(III) (PO-01) dopant. The phthalonitrile unit was an electron deficient unit and 9-phenylcarbazole was an electron rich unit of the IPNCz host. The phthalonitrile unit combined with the phenylcarbazole unit allowed strong charge transfer character by the donor-acceptor structure, delivering good thermal stability, bipolar carrier transport and proper triplet energy. Therefore, the IPNCz host assisted low driving voltage and high quantum efficiency close to 25% in the yellow phosphorescent device. • Isophthalonitrile based charge transfer host for yellow phosphors. • Donor-acceptor type charge transfer host for bipolar transport properties. • Low driving voltage and high efficiency in yellow phosphorescent devices.

Synthesis and characterization of new yellow emitting mixed heteroleptic Ir(III) complexes with solution-processed phosphorescent organic light-emitting diodes

Two new yellow emitting heteroleptic Ir(III) complexes are designed and synthesized for solution-processed yellow phosphorescent organic light-emitting diodes (PHOLEDs) with the amide-bridge core as main ligand and 2-phenylpyridine (ppy) as the ancillary ligand, named as bis[5-(2-ethylhexyl)−8-(trifluoromethyl)benzo[c][1,5]naphthyrid in-6(5)one](phenylpyridine)iridium(III) (Ir-1) and bis[5-(2-ethylhexyl)benzo[c][1,5naphthyridin-6(5H)one](phenylpyridi ne)iridium(III) (Ir-2). Ir-1 and Ir-2 complexes emit bright yellow emission in dichloromethane solution at 298 K. The newly synthesized Ir(III) complexes reveals the higher quantum yields over 40% and relatively short triplet lifetimes (0.12–0.15 μs), both which warrant to both complexes highly electroluminescence active materials. Both Ir(III) complexes were utilized as emitters for yellow solution-process PHOLEDs and obtained better performance. In particular, maximum external quantum efficiency (EQEmax) and maximum current efficiency (CEmax) of of 13.38% and 39.54 cd A−1 with the CIE (x, y) coordinates of (0.45, 0.53) was achieved for Ir-1 based yellow device. Furthermore, PHOLEDs with Ir-2 as an emitter attained EQEmax of 11.71% and CEmax of 37.60 cd A−1 with good color purity.

Synthesis and Characterization of New Phosphorescent Heteroleptic Iridium (III) Complex by Using Tetrazole as an Ancillary Ligand for Organic Light-Emitting Diodes

The yellow emitting tetrazole based heteroleptic iridium(III) complex, bis(diphenylquinoline)iridium(pyridyltetrazole) [(DPQ)2Ir(PyTz)], was synthesized and conformed by 1H-,13C NMR spectral techniques. The purity was also confirmed by HPLC. The thermal, electrochemical, photophysical and electroluminescent properties were intrinsically investigated. The Ir(III) complex is thermally more stable having thermal decomposition temperature (Td, 5% weight loss) more than 350°C and it shows very high glass transition temperature Tg-233°C. We have followed the easy and cost effective solution process for (DPQ)2Ir(PyTz) device fabrication and achieved better performance yellow phosphorescent organic light-emitting diodes (PhOLEDs), maximum external quantum efficiency (EQE) of 5.68%, luminance efficiency 12.63 cd/A, and CIE coordinate of (0.56, 0.43).

Yellow light direct hole-injection structure organic light-emitting device based on bis[2-(4-tert-butylphenyl) benzothiazolato-N,C2'] iridium (acetylicetonate) phosphor

The feasibility of adopting bis[2-(4-tert-butylphenyl) benzothIazolato-N,C-2'] iridium (acetylacetonate) [(t-bt) 2 Ir(acac)] in the direct hole-injection structure was investigated. Yellow phosphorescent organic light-emitting diodes based on (t-bt) 2 Ir(acac) with this structure were fabricated. The efficiencies of these diodes reached 27.51 lm/W and 53.33 cd/A at a brightness of 45 891 cd/m 2 . The realisation of these excellent efficiencies is ascribed to the characteristics of (t-bt) 2 Ir(acac) and the direct hole-injection structure.

Narrow bandgap host material for high quantum efficiency yellow phosphorescent organic light-emitting diodes doped with iridium(III) bis(4-phenylthieno[3,2-c]pyridine)acetylacetonate

A narrow bandgap host material, 4,5-di(9H-carbazol-9-yl)phthalonitrile (2CzPN), was used as a bipolar host material to improve the device performances of yellow phosphorescent organic light-emitting diodes(PHOLEDs). The device performances of the yellow PHOLEDs were optimized at a low doping concentration of 1%. A low turn-on voltage of 3.0V and high quantum efficiency of 19.3% were achieved using the 2CzPN host material and no efficiency roll-off of the device was observed up to 1000cd/m2 compared with 25% of reference device.

Highly efficient yellow phosphorescent organic light-emitting diodes with novel phosphine oxide-based bipolar host materials

Highly efficient yellow OLEDs based on bipolar host materials show a maximum current efficiency of 68.28 cd A−1, a maximum external quantum efficiency of 21.3% and a maximum power efficiency of 50.90 lm W−1 with low efficiency roll-off.

High external quantum efficiency in yellow and white phosphorescent organic light-emitting diodes using an indoloacridinefluorene type host material

High efficiency yellow phosphorescent organic light-emitting diodes were developed using spiro[fluorene-9,8′-indolo[3,2,1-de]acridine]-2,7-dicarbonitrile (ACDCN) as the host material for yellow emitting iridium(III) bis(4-phenylthieno[3,2-c]pyridinato-N,C2′)acetylacetonate (PO-01). The ACDCN host showed bipolar charge transport properties and efficient energy transfer to PO-01 dopant. Maximum external quantum efficiency of 25.7% and external quantum efficiency of 21.9% at 1000cd/m2 were obtained using ACDCN as the host material. In addition, high external quantum efficiency of 20.9% was achieved in the two color white phosphorescent organic light-emitting diodes with the PO-01 and iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,C2]picolinate doped ACDCN emitting layer.

A systematic identification of efficiency enrichment between thiazole and benzothiazole based yellow iridium(iii) complexes

A simple amendment of thiazole to benzothiazole based heteroleptic iridium(iii) complexes enhanced their efficiency in solution-processed yellow phosphorescent organic light-emitting diodes.

Highly efficient yellow phosphorescent organic light-emitting diodes for two-peak tandem white organic light-emitting diode applications

Reported herein are highly efficient yellow phosphorescent organic light-emitting diodes for tandem white organic light-emitting diode (WOLED) applications. The fabricated device structure was ITO/di-[4-(N,N-ditolyl-amino)-phenyl] cyclohexane(TAPC)(50 nm)/bis[2-(2-hydroxyphenyl)-pyridine]beryllium(Bepp2):iridium(III)bis(4-(4-t-butylphenyl)thieno [3,2-c] pyridinato-N,C2′)acetylacetonate)(Ir(tptpy)2(acac))(10 nm)/(1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene(TmPyPB)(40 nm)/LiF (1.5 nm)/Al(100 nm). The extremely high 25.0% external quantum efficiency (EQE), the 84.4 cd/A current efficiency, and the 90.7 lm/W power efficiency are reported, with Commission Internationale de L'Eclairage (CIE) coordinates of (0.49, 0.50). Such good performances are attributed to the good exciton confinement structure fabricated herein, and the highly efficient yellow dopant. The white tandem device was fabricated by utilizing this yellow device with the authors’ phosphorescent blue-OLED unit. An excellent 67.2 lm/W power efficiency and a 48.6% EQE with CIE coordinates of (0.39, 0.49) were obtained.

Simple Phenanthroimidazole/Carbazole Hybrid Bipolar Host Materials for Highly Efficient Green and Yellow Phosphorescent Organic Light-Emitting Diodes

By conjugating carbazole moiety to the different positions of the rigid skeleton 1,2-diphenyl-1H-phenanthro[9,10-d]imidazole, a series of hybrid bipolar phosphorescent hosts was synthesized, and their photophysical properties were investigated. The introduction of a rigid phenanthroimidazole moiety greatly improves their morphological stability, with high decomposition temperatures (Td) and high glass transition temperatures (Tg) in the range of 394–417 and 113–243 °C, respectively. The highly efficient green and orange phosphorescent organic light-emitting diodes (PhOLEDs) have been achieved by employing these compounds as the phosphorescent hosts. For the device of ITO/MoO3 (10 nm)/NPB (80 nm)/TCTA (5 nm)/mPhBINCP:9 wt % Ir(ppy)3 (20 nm)/TmPyPB (45 nm)/LiF (1 nm)/Al (100 nm), a maximum luminous efficiency (ηc,max) of 77.6 cd/A, maximum power efficiency (ηp,max) of 80.3 lm/W, and maximum external quantum efficiency (ηEQE,max) of 21% were obtained. Furthermore, these hosts are also applicable for the orange phosphorescent emitter (fbi)2Ir(acac), a yellow PhOLEDs with pPhBICP as host, for which a performance of ηc,max of 57.2 cd/A, ηEQE,max of 19.3%, and ηp,max of 59.8 lm/W was achieved. These results demonstrated that the phenanthroimidazole unit is an excellent electron-transporting group for constructing the bipolar phosphorescent host.