Non-doped Blue Organic Light-emitting Diodes Research Articles

New Phenanthro[9,10-d]oxazole-Based Fluorophores with Hybridized Local and Charge-Transfer Characteristics for Highly Efficient Blue Non-Doped OLEDs with Negligible Efficiency Roll-Off.

It is vital to develop highly efficient non-doped blue organic light-emitting diodes (OLEDs) with high color purity and low-efficiency roll-off for applications in display and lighting. Herein, two blue D-A fluorophores TPA-PO and TPA-DPO are designed and synthesized, in which phenanthro[9,10-d]oxazole (PO) acts as the acceptor and triphenylamine as the donor. TPA-PO and TPA-DPO display good thermal stability and efficient luminescence efficiency in neat film. Results based on photophysical property and theoretical calculation demonstrate that TPA-PO and TPA-DPO possess the hybridized local and charge-transfer (HLCT) feature, which can utilize the triplet exciton to achieve highly efficient electroluminance (EL). The non-doped OLEDs with TPA-PO/TPA-DPO as pure emissive layer show the uniform EL emission peak at 468 nm, corresponding to CIE coordinates of (0.168, 0.187) and (0.167, 0.167), respectively. The TPA-DPO-based non-doped OLEDs provide the maximum external quantum efficiency (EQE) of 7.99 % and high exciton utility efficiency of 48.4 %~72.6 %. Moreover, the TPA-DPO-based device exhibits low-efficiency roll-off, still maintaining the EQE of 6.03 % at the high luminance of 5000 cd m-2. Those findings state clearly that PO is a promising building block of blue fluorophore with a potential HLCT feature to be applied in non-doped OLEDs.

Efficiency boost in non-doped blue organic light-emitting diodes: Harnessing aggregation-induced emission – a comprehensive review

Revolutionizing OLEDs: AIE-driven efficiency boost in non-doped blue OLEDs showcased in this review. Novel strategies, experimental insights, and promising future prospects unveiled, propelling OLED technology forward.

Efficient Non-Doped Blue Electroluminescence Based on Phenanthroimidazole–Benzoylfluorene Hybrid Molecules with High Spin-Orbit Coupling and Balanced Charge Mobilities

Developing non-doped blue organic light-emitting diodes (OLEDs) with excellent photoluminescence quantum yield (PLQY), high exciton utilization efficiency (EUE) and balanced carrier mobility is an urgent challenge. Herein, two blue molecules...

Triphenylene-Based Emitters with Hybridized Local and Charge-Transfer Characteristics for Efficient Nondoped Blue OLEDs with a Narrowband Emission and a Small Efficiency Roll-Off.

Developing high-efficiency nondoped blue organic light-emitting diodes (OLEDs) with high color purity and low-efficiency roll-off is vital for display and lighting applications. Herein, we developed two asymmetric D-π-A blue emitters, PIAnTP and PyIAnTP, in which triphenylene is first utilized as a functional acceptor. The relatively weak charge transfer (CT) properties, rigid molecular structures, and multiple supramolecular interactions in PIAnTP and PyIAnTP can significantly enhance the fluorescence efficiency and suppress the structural relaxations to obtain a narrowband blue emission. The photophysical experiments and theoretical simulations reveal that they both exhibit a typical hybridized local and charge-transfer (HLCT) excited state and achieve high external quantum efficiency (EQE) via a "hot exciton" channel. As a result, PIAnTP- and PyIAnTP-based nondoped devices realize blue emission at 456 and 464 nm, corresponding to CIE coordinates of (0.16, 0.14) and (0.16, 0.19), narrow full width at half-maximums of 52 and 60 nm, and the high EQEs of 8.36 and 8.69%, respectively. More importantly, the PIAnTP- and PyIAnTP-based nondoped devices show small EQE roll-offs of only 5.9 and 2.4% at 1000 cd m-2, respectively. These results signify an advance in designing a highly efficient blue emitter for nondoped OLEDs.

Non-Doped Blue AIEgen-Based OLED with EQE Approaching 10.3 .

Aggregation-induced emission (AIE) luminogens (AIEgens) are attractive for the construction of non-doped blue organic light-emitting diodes (OLEDs) owning to their high emission efficiency in the film state. However, the large internal inversion rate (kIC (Tn) ) between high-lying triplet levels (Tn ) and Tn-1 causes a huge loss of triplet excitons, resulting in dissatisfied device performance of these AIEgens-based non-doped OLEDs. Herein, we designed and synthesized a blue luminogen of DPDPB-AC by fusing an AIEgen of TPB-AC and a DMPPP, which feature hot exciton and triplet-triplet annihilation (TTA) up-conversion process, respectively. DPDPB-AC successfully inherits the AIE feature and excellent horizontal dipole orientation of TPB-AC. Furthermore, it owes smaller kIC (Tn) than TPB-AC. When DPDPB-AC was applied in OLED as non-doped emitting layer, an outstanding external quantum efficiency of 10.3 % and an exceptional brightness of 69311 cd m-2 were achieved. The transient electroluminescent measurements and steady-state dynamic analysis confirm that both TTA and hot exciton processes contribute to such excellent device performance. This work provides a new insight into the design of efficient organic fluorophores by managing high-lying triplet excitons.

Rational molecular design of phenanthroimidazole–azine derivatives for efficient non-doped blue organic light-emitting diodes with low-efficiency roll-off

A family of phenanthroimidazole–azine derivatives (TrBPI, 4PyBPI, 2PyBPI, and 2PyTPI) bearing various kinds of azine acceptors (2,4-diphenyltriazine, 4,6-diphenylpyrimidine, and 2,6-diphenylpyrimidine) are successfully developed.

Approaches for Fabricating Tri‐ and Tetraphenylethene‐Based Blue Organic Light‐Emitting Diodes Using Donor–Acceptor and Non‐Donor–Acceptor Molecular Architectures

Light-Emitting Diodes Article number 2200206 by Samuthira Nagarajan and co-workers focuses on the design methodologies using triphenylethene- and tetraphenylethene-based non-donor–acceptor (non-D-A) and donor–acceptor (D-A) structures for non-doped blue organic light-emitting diodes (OLEDs). In the non-D-A system, triphenylamine and carbazole-based compounds demonstrate better performance, with the highest efficiency of 58300 and 5200 cd m–2. In the D-A system, imidazole-based compounds display the highest efficiency of 65150 cd m–2.

Asymmetric anthracene host decorated with benzothienocarbazole for high efficiency blue organic light-emitting diodes

In this work, we describe an asymmetric anthracene-based 5-(4-(10-phenylanthracen-9-yl)phenyl)-5H-benzo [4,5]thieno[3,2-c]carbazole (ATDBT) for high efficiency doped and non-doped organic light-emitting diodes (OLEDs). Anthracene triggered triplet-triplet annihilation and structurally induced bipolar characteristics of the ATDBT significantly accelerated the triplet to singlet up-conversion process. The fabricated devices eventually achieved high efficiency with a small efficiency roll-off at high luminance. The doped device with ATDBT as the host has a maximum external quantum efficiency (EQE) of more than 8%, pure-blue emission, and maximum luminance of more than 40,000 cd/m2. The non-doped ATDBT device also showed a high EQE of 4.9%. As a result, ATDBT-type asymmetric molecular structures are vital for the development of high-efficiency doped and non-doped blue OLEDs.

Improving the Efficiency of AIEgen-Based Nondoped Blue Organic Light-Emitting Diode by Rational Isomer Engineering

Improving the Efficiency of AIEgen-Based Nondoped Blue Organic Light-Emitting Diode by Rational Isomer Engineering

Aggregation-induced emission luminogen with excellent triplet-triplet upconversion efficiency for highly efficient non-doped blue organic light-emitting diodes.

By combining aggregation-induced emission (AIE) effect and a triplet-triplet upconversion (TTU) process, a blue emitter with excellent photoluminescence quantum efficiency and high upconversion efficiency in the film state is developed, from which a highly efficient non-doped blue TTU organic light-emitting diode (TTU-OLED) was realized.

Highly efficient non-doped blue OLED based on perylene

An efficient non-doped blue organic light-emitting diode with several-nanometer-thick easy-to-aggregate fluorescent material perylene is reported in which two thin layers of perylene as blue emitters are located at both the sides of ambipolar material, 4,4′-N,N′-dicarbazole-biphyenyl (CBP), and the aggregation behavior of perylene in films is prevented. The maximum luminance and external quantum efficiency are 16 000 ± 600 cd/m2 and 3.0% ± 0.02% (3.70 ± 0.03 cd/A), respectively. Commission Internationale de l'Eclairage co-ordinates are basically x = 0.14 and y = 0.15. Although Föster energy transfer from CBP to perylene is efficient, the carrier confining induced exciton direct formation mechanism is considered to dominate the process of electroluminescence.

Doped and non-doped blue organic light-emitting diodes based on AIEgens with high exciton utilization efficiency and external quantum efficiency

Non-doped OLEDs with NSPI-DVP and CNSPI-DVP show high exciton utilization efficiency of 36.00 and 64.00%, power efficiency of 4.99 and 4.72 lm W−1, external quantum efficiency of 3.2 and 5.3% and current efficiency of 5.61 and 5.03 cd A−1, respectively.

Through-Space Charge-Transfer Polynorbornenes with Fixed and Controllable Spatial Alignment of Donor and Acceptor for High-Efficiency Blue Thermally Activated Delayed Fluorescence.

Through-space charge transfer polynorbornenes with fixed and controllable spatial alignment of donor and acceptor in edge-to-face/face-to-face stacking patterns are developed for achieving high-efficiency blue thermally activated delayed fluorescence (TADF). The alignment is realized by using the cis, exo-configuration of norbornene to confine donor and acceptor in close proximity, and utilizing orthogonal and dendritic structures of donors to provide either perpendicular or parallel stacking motif relative to acceptors. Compared to edge-to-face counterparts, polynorbornenes with face-to-face aligned donor and acceptor exhibit much larger oscillator strength and higher photoluminescence quantum yield. The resulting polymers exhibit deep blue (422 nm) to sky blue (482 nm) emission and TADF effect with reverse intersystem crossing rates of 0.4-5.9×106 s-1 , giving the maximum external quantum efficiency of 18.8 % for non-doped blue organic light-emitting diodes by solution process.

Pyrene[4,5-d]imidazole-Based Derivatives with Hybridized Local and Charge-Transfer State for Highly Efficient Blue and White Organic Light-Emitting Diodes with Low Efficiency Roll-Off.

A family of pyrene[4,5-d]imidazole derivatives, PyPA, PyPPA, PyPPAC, and PyPAC, with different excited states are successfully developed. Among them, PyPPA and PyPPAC possess hybridized local and charge-transfer (HLCT) state, endowing them with pure blue fluorescence as well as high quantum yields. The nondoped organic light-emitting diode (OLED) based on PyPPA displays Commission Internationale de L'Eclairage coordinates of (0.14, 0.13) and achieves a maximum external quantum efficiency (EQE) of 8.47%, which are among the highest value reported to date for nondoped blue HLCT OLEDs. The nondoped OLED based on PyPPAC exhibits a maximum luminance of 50,046 cd m-2 located in the blue region with CIE coordinates of (0.15, 0.21) and an EQE of 6.74% even when the luminance reached over 10,000 cd m-2. In addition, they both reveal ultimate exciton utilizing efficiencies of nearly 100%. The potential of a blue emitter of PyPPA with an HLCT character for application in white OLED (WOLED) is further tested. The efficient two-color hybrid warm WOLED is successfully achieved, which provides the total EQE, power efficiency, and current efficiency of up to 21.19%, 61.46 lm W-1, and 62.13 cd A-1, respectively. The nondoped blue OLEDs and hybrid WOLEDs present good color stabilities with low efficiency roll-offs. Our results prove that taking advantage of the HLCT state, nondoped blue OLEDs as well as hybrid WOLEDs with high performance could be realized, which have a promising prospect for the displays and lightings in the future.

Achievement of High‐Performance Nondoped Blue OLEDs Based on AIEgens via Construction of Effective High‐Lying Charge‐Transfer State

AbstractThere remains an urgent demand for high‐quality blue luminogens that can simultaneously achieve high photoluminescence quantum yield (PLQY) in film and high exciton utilization efficiency (EUE) in the electroluminescence (EL) process. In this study, a referable molecular design strategy is developed for blue luminogens via constructing low‐lying locally excited (LE) state with an aggregation‐induced emission (AIE) characteristic and high‐lying charge‐transfer (CT) state for the effective triplet‐to‐singlet conversion channel. 2TriPE‐BPI‐MCN with the insertion of p‐cyano and o‐methyl groups is designed to compare with its matrix framework (2TriPE‐BPI). They have analogous properties of the lowest singlet (S1) states with blue emission and free of concentration quenching in film; however, 2TriPE‐BPI‐MCN exhibits unusual response for hydrostatic pressure owing to its S2 state CT characteristics. Therefore, 2TriPE‐BPI‐MCN can harness more electrogenerated excitons than 2TriPE‐BPI, resulting in a better EL performance in nondoped blue organic light‐emitting diodes (OLEDs) (CIEx,y = 0.153, 0.147) with high external quantum efficiency of 4.6% and negligible efficiency roll‐off. These findings could open a feasible avenue to develop high‐quality blue luminogens for high‐performance nondoped blue OLEDs.

Utilizing Electroplex Emission to Achieve External Quantum Efficiency up to 18.1% in Nondoped Blue OLED.

For the first time, electroplex emission is utilized to enhance the performance of nondoped blue organic light-emitting diodes (OLEDs). By decorating the twisted blue-emitting platform and adjusting the electronic structure, three molecules of 3Cz-Ph-CN, 3Cz-mPh-CN, and 3Ph-Cz-CN with a donor-acceptor structure are synthesized and investigated. When external voltage is applied, electroplex emission, which contributes to the emission performance of OLED, can be realized at the interface between the emitting layer and the electron-transporting layer. Accordingly, high external quantum efficiency of 18.1% can be achieved, while the emission wavelength of the device can be controlled in the blue region. Our results provide the possibility to enhance the performance of OLED through electroplex emission, in addition to the generally investigated thermally activated delayed fluorescence (TADF). Excitedly, when 3Ph-Cz-CN is used as host material in orange-emitting phosphorous OLEDs (PO-01 as the dopant), unprecedented high external quantum efficiency of 27.4% can also be achieved.

Highly efficient nondoped blue organic light-emitting diodes based on a star-group tetraphenylethylene-substituted aggregation-induced-emission-active organic fluorescent small molecules

Tetraphenylethene (TPE) is a star group exhibiting an excellent aggregation-induced emission (AIE) effect. Although significant progress has been made in the field of organic electroluminescence (EL) based on TPE-substituted emitters, highly efficient and high-color-purity TPE-substituted blue fluorophores with the AIE effect are still very rare. In this paper, a simple and effective molecule—N-phenyl-N-(4-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)-4′-(1,2,2-triphenylvinyl)-[1,1′-biphenyl]-4-amine (TPETPAPI)—was designed and synthesized using triphenylamine (donor), phenanthroimidazole (acceptor), and tetraphenylethylene (AIE generator). In tetrahydrofuran solution, the molecule emits little light and the quantum efficiency is low (1.3%); however, the fluorescence is enhanced in the film (73%), exhibiting remarkable AIE properties, thus enabling TPETPAPI to be used in future applications in organic light-emitting diodes. The nondoped device exhibits a low turn-on voltage of 3.0 V, a maximum luminance of 10780 cd m−2, maximum current efficiency of 12.20 cd A−1, and maximum power efficiency of 11.95 lm W−1, with an EL peak at 476 nm. TPETPAPI exhibits the most impressive EL performance reported to date for a TPE-substituted blue fluorophore with AIE' characteristics.

Novel blue fluorescent materials for high-performance nondoped blue OLEDs and hybrid pure white OLEDs with ultrahigh color rendering index

Pure blue luminogens that can be applied in high-efficiency nondoped blue organic light-emitting diodes (OLEDs) and act as main component to generate white OLEDs with high color rendering index (CRI) simultaneously are rarely reported. Herein, two blue emitters, TPAATPE and PPIATPE, consisting of triphenylamine/phenanthroimidazole and tetraphenylethene-substituted anthracene with asymmetric structures are designed and synthesized. The nondoped OLED using TPAATPE as the emitter exhibits pure blue emission with the maximum external quantum efficiency (EQE) of 6.97% and Commission International de L'Eclairage (CIE) coordinates of (0.15, 0.16). Employing TPAATPE as the blue-emitting component, combined with a thermally activated delayed fluorescent (TADF) molecule PTZMes2B, which is adopted as the green emitter and the host for phosphors to modulate the long wavelength emission, a series of highly efficient hybrid white OLEDs are successfully achieved. Among them, the two-color white OLED exhibits eye-friendly warm white light with a maximum forward-viewing EQE of 25.2%. In particular, the three-color white OLED achieves pure white emission with CIE coordinates of (0.34, 0.38), a maximum forward-viewing EQE of 25.3% and an ultrahigh CRI of 92. All of nondoped blue OLEDs and hybrid white OLEDs exhibit very small efficiency roll-offs with excellent color stabilities. To the best of our knowledge, these results are among the best outcomes for white OLEDs reported so far.

Highly efficient nondoped blue organic light-emitting diodes with high brightness and negligible efficiency roll-off based on anthracene-triazine derivatives

A nondoped device based on the PIAnTAZ emitter shows blue electroluminescence with a maximum EQE of 7.96%, a maximum luminance of 58 675 cd m−2 and negligible efficiency roll-offs.

Combining Charge-Transfer Pathways to Achieve Unique Thermally Activated Delayed Fluorescence Emitters for High-Performance Solution-Processed, Non-doped Blue OLEDs.

Two efficient blue thermally activated delayed fluorescence compounds, B-oCz and B-oTC, composed of ortho-donor (D)-acceptor (A) arrangement were designed and synthesized. The significant intramolecular D-A interactions induce a combined charge transfer pathway and thus achieve small ΔEST and high efficiencies. The concentration quenching can be effectively inhibited in films of these compounds. The blue non-doped organic light emitting diodes (OLEDs) based on B-oTC prepared from solution processes shows record-high external quantum efficiency (EQE) of 19.1 %.