Efficient White Organic Light-emitting Diodes Research Articles

Highly efficient fluorescent and hybrid white organic light-emitting diodes based on a bimolecular excited system: publisher's note.

This publisher's note contains a correction to Opt. Lett.48, 5771 (2023)10.1364/OL.506371.

Highly efficient white organic Light-Emitting diodes utilizing intermolecular interaction based on molecular geometry between host and deep blue Pt(Ⅱ) complex

Previous studies on white organic light-emitting diodes (WOLEDs) using a single Pt dopant relied on square-planar Pt complexes, exhibiting various emission characteristics due to ligand-centered π-π interactions. However, this approach limits the range of the materials selections to those with excimer or aggregation-induced emission (AIE) properties.In this study, a new method for creating WOLEDs with a single Pt dopant is proposed. We observed the emergence of an intermolecular interaction, specifically the formation of an exciplex due to π-π interaction between the n-host (ET) and the Pt complex, leading to a low-energy yellow emission. By varying the mixing ratio of ET and Pt complex, a spectrum of emissions ranging from pure blue to yellow was achievable. Consequently, we constructed 3-stack tandem devices, leveraging color variations based on the ET:Pt ratio. As a result, we successfully achieved a cool white emission with a Color Rendering Index (CRI) of 66.7, International Commission on Illumination (CIE) coordinates of (0.294, 0.380). Additionally, through optimization of the device structure, external quantum efficiency (EQE) was enhanced from 18.3% to 21.9%. This novel and simple device architecture adjusting intermolecular interaction based on molecular geometry between ET and Pt(II) complex provides a solution to materials limitations in WOLEDs.

Efficient all-fluorescence white organic light-emitting diodes with superior color stability and low efficiency roll-off employing matrix-free blue emitting layers

All-fluorescence WOLEDs comprising a matrix-free TADF blue emitting layer simultaneously reach low efficiency roll-off and extremely color stable electroluminescence spectra.

Simple and efficient non-doped deep-blue and white organic light-emitting diode based on hybridized local and charge transfer (HLCT) materials

The first all HLCT-based non-doped white OLED is demonstrated, which realizes excellent EL performance with the maximum EQE exceeding 5% and obtains a balanced white light emission with maximum CRI reaching 84.

Highly efficient fluorescent and hybrid white organic light-emitting diodes based on a bimolecular excited system.

A bimolecular excited system is considered as a promising candidate for developing white organic light-emitting diodes (WOLEDs) with reduced phosphorescent components. However, for actualizing high-performance WOLED, little attention has been paid to electromers compared to exciplexes. Herein, we construct the bimolecular excited system to prepare fluorescent WOLEDs by combining the electromer emission with the exciplex emission, achieving a maximum power efficiency of 11.8 lm/W with a color rendering index (CRI) of over 80. Furthermore, phosphorescent dopants are doped into an exciplex host to construct hybrid WOLEDs. The fabricated complementary-color and three-color devices achieve maximum efficiencies of 55.3 cd/A (46.8 lm/W) and 34.1 cd/A (26.8 lm/W), respectively. The spectral coverages of WOLEDs are broadened by the bimolecular excited system, and CRIs are further improved at high luminance. Our strategy may bring light to the future development of highly efficient WOLEDs with economy and sustainability.

Efficient, Color-Stable, and Long-Lived White Organic Light-Emitting Diodes Utilizing Phosphorescent Molecular Aggregates.

Highly efficient and stable single-stack hybrid white organic light-emitting diode (WOLED) devices are developed using two emissive layers: one with amber-colored phosphorescent molecular-aggregate emission from the Pd(II) complex, Pd(II) 7-(3-(pyridine-2-yl-κN)phenoxy-κC)(benzo-κC)([c]benzo[4,5]imidazo-κN)[1,2-a][1,5]naphthyridine, Pd3O8-Py5, and the other with blue fluorescence emission. An optimized device structure achieves high color stability under various current densities, an external quantum efficiency (EQE) of 45.5%, a power efficiency of 97.4 Lm W-1 , and an estimated LT95 (operational time to 95% of the initial luminance) of 50 744 h at an initial luminance of 1000cd m-2 .

Tripyridylbenzene-based blue dendrimer emitters for efficient solution-processable single-emissive-layer hybrid white organic light-emitting diodes

A series of light-emitting dendrimers T42Bn, T24Bn, T26Bn and T35Bn based on electron-donating units of the second-generation butyicarbazoles (G2Cz) as dendrons and electron-withdrawing core of tripyridylbenzene (TPB) were designed and synthesized. The desirable blue luminogens were obtained due to the rational molecular design based on the twisted skeleton of all the molecules despite the donors of G2Cz moieties connected to the central acceptors of TPB via a para-phenylene bridge. Their thermal, photophysical, density functional theory calculation and electrochemical properties were fully investigated. Thanks to the excellent thermal stability, film-forming ability as well as the favourable energy levels of the dendrimers, efficient solution-processed hybrid white organic light-emitting diodes (WOLEDs) were achieved by employing these blue dendrimers and the orange emitter of (acetylacetonato)-bis[2-(thieno [3,2-c]pyridin-4-yl)phenyl]iridium(III) (PO-01) as an emitting layer (EML). Among them, the device based on T42Bn exhibited the highest maximum current efficiency (CEmax) of 10.25 cd/A with a maximum external quantum efficiency (EQEmax) of 3.94% and Commission International de I'Eclairage (CIE) coordinates of (0.34, 0.39), benefiting from the largest ƞPLQY and the highest electron transport capability of T42Bn and thus the enhancement of charge carrier balance in the device. In addition, the CIE coordinates of all the single-emitting-layer fluorescence/phosphorescence hybrid devices are very close to the benchmark white region of (0.33, 0.33). Our findings demonstrate the potential candidates of the solution-processable blue dendronized emitters for applications in full-color flat-panel displays and white lighting.

Highly efficient white organic light-emitting diodes based on balanced bipolar-transporting blue hybridized local charge transfer fluorophores

A super-efficient hybrid WOLED was achieved by blending the HLCT-based blue fluorescent molecule (TPACFOXZ) with a yellow phosphorescent molecule.

Highly efficient single emitter white phosphorescent organic light-emitting diodes based on Pt(ii) emitters

We fabricate highly efficient white platinum(ii) emitters with high CRI for phosphorescent OLEDs using new tetradentate ligands prepared with difluoropyrido-pyridyl and meta-xylyl amine linkers.

Improving excitons utilization of blue thermally activated delayed fluorescence emitter to achieve highly efficient solution-processed hybrid white organic light-emitting diodes

5-(5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-10,15-diphenyl-10,15-dihydro-5H-diindolo[3,2-a:3′,2′-c]carbazole (DBA-DI) with high triplet energy was utilized as efficient blue emission dopant to construct solution-processed thermally activated delayed fluorescence-phosphorescence (TADF-phosphorescence) hybrid white organic light-emitting diodes (WOLEDs). Meanwhile, a series of TADF-phosphorescence hybrid WOLEDs composed of bis(2-phenylquinoline) (2,2,6,6-tetramethylheptane-3,5-dionate)iridium(III) (PQ2Ir(dpm)), tris(2-(4-tolyl)-phenylpyridine)iridium (Ir(mppy)3) and DBA-DI are successfully developed by introducing the co-host system consist of poly(N-vinylcarbazole) (PVK) and 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (26DCzPPy) with high color rendering index (CRI) and improving the utilization of triplet excitons. Furthermore, energy transfer processes among different emitters were investigated in detail based on absorbance spectra, photoluminescence and transient photoluminescence spectra. Ultimately, the Commission Internationale de I'Eclairage coordinates of the optimum solution-processed WOLEDs in warm-white emission region are (0.41, 0.41) and high CRI is 82. Furthermore, the same device realized outstanding efficiencies of 32.14 cd A−1, 21.00 lm W−1 and 15.1% at high brightness of 1000 cd m−2.

Efficient hybrid white organic light-emitting diodes with superior color stability and slow efficiency roll-off based on ultrathin emitting layer structures

In this work, high-performance hybrid white organic light-emitting diodes (WOLEDs) with high efficiencies, slow roll-off and excellent color stability were realized by strategically inserting ultrathin red phosphorescent emitter film into bluish-green thermally activated delayed fluorescent (TADF) light-emitting layer (EML). Experimental results demonstrated that the introduction of ultrathin phosphor film helps to harvest superfluous triplet excitons within bluish-green EML and relieve local exciton accumulation-induced quenching, thereby guaranteeing high exciton utilization probability. Besides, the strong holes' trapping of ultrathin layer leads to improved carriers balance, thus realizing stable recombination zone. Finally, the optimal hybrid WOLED obtained the maximum current efficiency (ηc), power efficiency (ηp) and external quantum efficiency (EQE) of 63.84 cd A−1, 66.06 lm W−1 and 28.16%, respectively. At the brightness of 1000 cd m−2, ηc, ηp and EQE as high as 57.14 cd A−1, 49.88 lm W−1 and 25.23%, respectively, can still be remained by the same device, manifesting slow efficiency roll-off. In addition, the resulting WOLED displayed excellent color stability with slightly shifted Commission Internationale de l’Eclairage coordinates (CIEx,y) from (0.43, 0.44) at 1000 cd m−2 to (0.41, 0.43) at 10000 cd m−2.

Engineering of interface exciplex system for highly efficient white organic light-emitting diodes based on single-emission-layer architecture

Highly efficient white organic light-emitting diodes (WOLEDs) with low turn-on voltages and efficiency roll-offs actualized by simplified structure are still a great challenging subject. Herein, the interface exciplex structure is manipulated to achieve high-efficiency phosphorescent WOLEDs with single-emitting-layer for the first time. The key to our strategy is the enhancement of Förster energy transfer from interface exciplex to guest and well restriction of exciton recombination region. By incorporating complementary emitters into acceptor layer, color-stable WOLEDs with low turn-on voltages are demonstrated. The maximum efficiencies of 81.1 cd A −1 and 101.9 lm W −1 are realized in the optimized device with suppressed roll-off. These results provide an effective approach to construct high performance WOLEDs based on simplified architecture.

Highly efficient solution-processed white organic light-emitting diodes based on a co-host system by controlling energy transfer among different emitters

Efficient solution-processed white organic light-emitting diodes with FIrpic, Ir(mppy)3 and (MDQ)2Ir(acac) as the blue, green and red emitters, respectively, were realized by employing TcTa and CzSi as hosts.

Improvement of exciton utilization by suppressing exciton leakage for high efficiency blue and white organic light-emitting diodes

Improvement of exciton leakage by insertion of DMAC-DPS results in the successful preparation of high-efficiency blue OLEDs and WOLEDs.

Highly efficient blue and white phosphorescent organic light-emitting diodes with low-efficiency roll-off utilizing thermally activated delayed fluorescent-based co-host architecture

Highly efficient blue phosphorescent organic light-emitting diodes (PhOLEDs) with reduced efficiency roll-off are still challenging. A blue phosphor of (cyanato-κO)[3,5-difluoro-2-(2-pyridinyl-κN)phenyl-κC][[1,1'-(1,3-phenylene-κC2)bis[3-butyl-2,3-dihydro-1H-imidazolato-κC2]](5-)]-iridium complex is utilized as the blue emitter to fabricate highly efficient blue PhOLEDs. Especially, it is first utilized for white PhOLEDs with superior device performance. The realized blue PhOLED employing a novel TADF co-host system achieves maximum power efficiency (PE) of 43.3 lm/W and the PE still remains 26.3 lm/W at 1000 cd/m2, which are 1.9 and 2.5 times higher than that of blue PhOLED using conventional phosphor single-host structure. Furthermore, the current efficiency (CE) roll-off of the blue PhOLED with TADF co-host architecture is only 2.2% at 1000 cd/m2, which can be assigned to the balanced charge carriers injection and transport. The final white device obtained the maximum CE of 46.1 cd/A, PE of 48.1 lm/W, and a low roll-off of 1.9% at 1000 cd/m2. We also systemically investigate the energy transfer mechanism and exciton distribution of the devices. It was found that our proposed device structure could effectively promote the Förster energy transfer mechanism and the even distribution of excitons. We firmly believe that our work may bring light to the future development of highly efficient PhOLEDs with simultaneous low roll-off.

Achieving High Electroluminescence Efficiency and High Color Rendering Index for All‐Fluorescent White OLEDs Based on an Out‐of‐Phase Sensitizing System

AbstractSensitizing conventional fluorescence (CF) dopants with thermally activated delayed fluorescence (TADF) materials has achieved considerable progress, by which the advantages of TADF materials and CF dopants can be fully harnessed. However, the usually used co‐phase configuration of CF dopant‐engaged sensitizing systems often encounters exciton loss due to Dexter energy transfer (DET). Herein, an effective out‐of‐phase configuration is proposed to sensitize CF dopants in the fabrication of white organic light‐emitting diodes (WOLEDs). Based on a new efficient sky‐blue TADF luminogen DCP‐BP‐DPAC which has an electroluminescence (EL) peak at 486 nm and an EL efficiency of 26.6%, a green TADF material BDMAC‐XT, and a red CF dopant DBP sensitized by BDMAC‐XT through an out‐of‐phase configuration without interlayer, efficient WOLEDs are successfully fabricated. By further adopting orange TBRB or 4CzTPNBu as intermediate sensitizers, more efficient energy transfer to DBP is achieved via Förster energy transfer. Through step‐by‐step energy transfer and elimination of excess DET process, high‐performance all‐fluorescent WOLEDs are achieved, providing excellent EL efficiencies over 23.0%, and highly stable white light with a high color rendering index of 87. The outstanding EL performance and high‐quality emission color demonstrate the great potential of the proposed out‐of‐phase design for sensitizing systems of WOLEDs.

Efficient triplet harvest for orange-red and white OLEDs based exciplex host with different donor/acceptor ratios

Abstract Highly efficient orange-red and white organic light-emitting diodes (OLEDs) based exciplex host with different donor/acceptor ratios and doping concentrations are fabricated for efficient triplet excitons harvest. As a result, the maximum efficiency is achieved at 5:5 ratios exciplex host in orange-red OLEDs with current efficiency, power efficiency and external quantum efficiency (EQE) of 37.0 cd/A, 37.3 lm/W and 18.3%, respectively. Furthermore, the white OLEDs under two different doping concentrations give warm white (0.48, 0.41) and cool white (0.28, 0.37) emission with maximum current efficiencies, power efficiencies and EQEs of 38.3/37.6 cd/A, 41.3/43.7 lm/W and 17.8/16.6%, respectively. We found that the triplet exciton harvest on exciplex host through reverse intersystem crossing process and efficient energy transfer are responsible for the high device efficiency.

Exciton engineering based on star-shaped blue thermally activated delayed fluorescence emitters for efficient white organic light-emitting diodes

Accurate exciton allocation in thermally activated delayed fluorescence (TADF) white organic light-emitting diodes (OLEDs) was realized to achieve the efficient efficient white emission.

Rational arrangement of multiple exciplex hosts for highly efficient white organic light-emitting diodes

Designing a novel exciplex host and arranging rational multiple-exciplex hosts in emissive layers.Two and three color WOLEDs based on multiple exciplex hosts exhibited maximum EQEs of 30.9% and 27.0%, respectively. Remarkedly, their EQEs remained at 22.1% and 21.3% at a high luminance of 5000 cd m−2.

High efficiency and long lifetime fluorescent white organic light-emitting diodes by phosphor sensitization to strategically manage singlet and triplet excitons

The positions of the phosphor-sensitized yellow EML from the exciton recombination zone were controlled to strategically utilize singlet and triplet excitons for blue and yellow emissions to realize high-performance fluorescent WOLEDs.