Modulating Photo‐ and Electroluminescence in a Stimuli‐Responsive π‐Conjugated Donor–Acceptor Molecular System

Functional organic materials that display reversible changes in fluorescence in response to external stimuli are of immense interest owing to their potential applications in sensors, probes, and security links. While earlier studies mainly focused on changes in photoluminescence (PL) color in response to external stimuli, stimuli‐responsive electroluminescence (EL) has not yet been explored for color‐tunable emitters in organic light‐emitting diodes (OLEDs). Here a stimuli‐responsive fluorophoric molecular system is reported that is capable of switching its emission color between green and orange in the solid state upon grinding, heating, and exposure to chemical vapor. A mechanistic study combining X‐ray diffraction analysis and quantum chemical calculations reveals that the tunable green/orange emissions originate from the fluorophore's alternating excited‐state conformers formed in the crystalline and amorphous phases. By taking advantage of this stimuli‐responsive fluorescence behavior, two‐color emissive OLEDs were produced using the same fluorophore in different solid phases.     

Efficient Non‐doped Blue Fluorescent Organic Light‐Emitting Diodes Based on Anthracene–Triphenylethylene Derivatives

The development of efficient blue materials has been a continuous research topic in the field of organic light‐emitting diodes (OLEDs). In this paper, three aggregation‐induced emission enhancement active blue emitters, PIAnTPE, TPAAnTPE and CzAnTPE, are successfully synthesized by attaching a triphenylethylene unit and phenanthroimidazole/triphenylamine/carbazole moieties to the 9,10‐positions of anthracene, respectively. The three compounds exhibit good thermal stabilities, appropriate for the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels and display high photoluminescence quantum yields (PLQYs) of 65, 70 and 46 % in the solid state. Non‐doped blue devices using PIAnTPE, TPAAnTPE and CzAnTPE as the emitting layers show good electroluminescent performances, with the maximum external quantum efficiencies (EQEs) of 4.46, 4.13 and 4.04 %, respectively. More importantly, EQEs of all the three devices can be still retained when the luminescence reaches 1000 cd m^?2, exhibiting quite small efficiency roll‐offs in the non‐doped OLEDs.     

BF2‐Chelate Complexes of 6‐(4‐Iodophenyl)‐2,3,4,8,9,10‐hexamethyldipyrrin and 2‐(4‐Iodobenzoyl)‐3,4,5‐trimethylpyrrole: Fluorescent Dyes with a Chemical Anchor Group

The one‐pot condensation/coordination reaction of 4‐iodobenzoylchloride, 2,3,4‐trimethylpyrrole and BF₃ × Et₂O yields the BF₂ chelate complexes of the 1:1 condensation product 2‐(4‐iodobenzoyl)‐3,4,5‐trimethylpyrrole and of the 1:2 product 6‐(4‐iodophenyl)‐2,3,4,8,9,10‐hexamethyldipyrrin, as separable compounds in 6 and 38 % yield, respectively. Both new boron derivatives are fluorescent already upon exitation with ambient light. While the fluorescence quantum yield of the benzoyl derivative is very low, this value is significantly higher for the related boron dipyrrin (BODIPY) derivative. Single crystal X‐ray diffraction studies of both compounds reveal that the reason for these deviating physical properties are structural in nature. For the BODIPY an essentially flat structure of the fluorophor has been established, in addition to restricted rotation of the 4‐iodophenyl substituent, so that no conformational dynamic facilitates radiationless deactivations. The 1:1 condensation product on the other hand allows a fast equilibration of the photophysical exitation by dynamic processes and therefore exhibits a low fluorescence quantum yield. Both luminophores contain an iodoaryl moiety with potential uses for further functionalization and bioconjugation.     

High‐Performance Non‐doped OLEDs with Nearly 100 % Exciton Use and Negligible Efficiency Roll‐Off

Non‐doped organic light‐emitting diodes (OLEDs) possess merits of higher stability and easier fabrication than doped devices. However, luminescent materials with high exciton use are generally unsuitable for non‐doped OLEDs because of severe emission quenching and exciton annihilation in neat films. Herein, we wish to report a novel molecular design of integrating aggregation‐induced delayed fluorescence (AIDF) moiety within host materials to explore efficient luminogens for non‐doped OLEDs. By grafting 4‐(phenoxazin‐10‐yl)benzoyl to common host materials, we develop a series of new luminescent materials with prominent AIDF property. Their neat films fluoresce strongly and can fully harvest both singlet and triplet excitons with suppressed exciton annihilation. Non‐doped OLEDs of these AIDF luminogens exhibit excellent luminance (ca. 100000 cd m^?2), outstanding external quantum efficiencies (21.4–22.6 %), negligible efficiency roll‐off and improved operational stability. To the best of our knowledge, these are the most efficient non‐doped OLEDs reported so far. This convenient and versatile molecular design is of high significance for the advance of non‐doped OLEDs.     

Synthesis and Characteristics of Organic Red‐Emissive Materials Based on Phenanthro[9,10‐d]imidazole

Red emission is one of the three primary colors that are essential for the realization of full‐color displays and solid‐state lightings. A high solid‐state efficiency is a crucial factor for the applications in organic light‐emitting diodes (OLEDs). In this work, two new donor‐acceptor‐donor type phenanthro[9,10‐d]imidazole (PIM)‐based derivatives, (2Z,2′Z)‐2,2′‐(1,4‐phenylene)bis(3‐(4‐(1‐phenyl‐1H‐phenanthro[9,10‐d]imidazol‐2‐yl)phenyl)acrylonitrile) ( PIDSB ) and 2,3‐bis(4′‐(1‐phenyl‐1H‐phenanthro[9,10‐d]imidazol‐2‐yl)‐[1,1′‐biphenyl]‐4‐yl)fumaronitrile ( PIDPh ), are designed and synthesized. Both of them possess high thermal stabilities. PIDPh shows typical characteristics of aggregation‐induced emission enhancement, while PIDSB displays an aggregation‐caused quenching effect. They both exhibit significant red‐shifted emissions compared with PIM owing to intramolecular charge transfer. In the film state, the emission peaks of PIDSB and PIDPh are located at 538 nm and 605 nm with high photoluminescent quantum yields of 63.82 % and 41.26 %, respectively. The non‐doped OLED using PIDPh as the active layer shows the maximum external quantum efficiency of 2.06 % with a very low efficiency roll‐off, and exhibits the electroluminescent peak at 640 nm with a Commission Internationale de l′Éclairage coordinate of (0.617,0.396), meeting well the criteria of red OLEDs.     

Efficient Nondoped Pure Blue Organic Light‐Emitting Diodes Based on an Anthracene and 9,9‐Diphenyl‐9,10‐dihydroacridine Derivative

Organic light‐emitting diodes (OLEDs) have been greatly developed in recent years owing to their abundant advantages for full‐color displays and general‐purpose lightings. Blue emitters not only provide one of the primary colors of the RGB (red, green and blue) display system to reduce the power consumption of OLEDs, but are able able to generate light of all colors, including blue, green, red, and white by energy transfer processes in devices. However, it remains a challenge to achieve high‐performance blue electroluminescence, especially for nondoped devices. In this paper, we report a blue light emitting molecule, DPAC‐AnPCN, which consists of 9,9‐diphenyl‐9,10‐dihydroacridine and p‐benzonitrile substituted anthracene moieties. The asymmetrically decoration on anthracene with different groups on its 9 and 10 positions combines the merits of the respective constructing units and endows DPAC‐AnPCN with pure blue emission, high solid‐state efficiency, good thermal stability and appropriate HOMO and LUMO energy levels. Furthermore, DPAC‐AnPCN can be applied in a nondoped device to effectively reduce the fabrication complexity and cost. The nondoped device exhibits pure blue electroluminescence (EL) locating at 464 nm with CIE coordinates of (0.15, 0.15). Moreover, it maintains high efficiency at relatively high luminescence. The maximum external quantum efficiency (EQE) reaches 6.04 % and still remains 5.31 % at the luminance of 1000 cd m^?2 showing a very small efficiency roll‐off.     

High Power Efficiency Blue‐to‐Green Organic Light‐Emitting Diodes Using Isonicotinonitrile‐Based Fluorescent Emitters

Herein, 9,10‐dihydro‐9,9‐dimethylacridine (Ac) or phenoxazine (PXZ)‐substituted isonicotinonitrile (INN) derivatives, denoted as 2AcINN , 26AcINN , and 26PXZINN , were developed as a series of thermally activated delayed fluorescence (TADF) emitters. These emitters showed reasonably high photoluminescence quantum yields of 71–79 % in the host films and high power efficiency organic light‐emitting diodes (OLEDs). Sky‐blue emitter 26AcINN exhibited a low turn‐on voltage of 2.9 V, a high external quantum efficiency (η _ext) of 22 %, and a high power efficiency (η _p) of 66 lm W⁻¹ with Commission Internationale de l′Eclairage (CIE) chromaticity coordinates of (0.22, 0.45), whereas green emitter 26PXZINN exhibited a low turn‐on voltage of 2.2 V, a high η _ext of 22 %, and a high η _p of 99 lm W⁻¹ with CIE chromaticity coordinates of (0.37, 0.58). These performances are among the best for TADF OLEDs to date.     

Achieving Pure Deep‐Blue Electroluminescence with CIE y≤0.06 via a Rational Design Approach for Highly Efficient Non‐Doped Solution‐Processed Organic Light‐Emitting Diodes

Deep‐blue fluorescent emitters with Commission Internationale de l'Eclairage (CIE) y≤0.06 are urgently needed for high‐density storage, full‐color displays and solid‐state lighting. However, developing such emitters with high color purity and efficiency in solution‐processable non‐doped organic light‐emitting diodes (OLEDs) remains an important challenge. Here, we present the synthesis of two new deep‐blue fluorescent emitters ( AFpTPI and AFmTPI ) based on 10‐(9,9‐diethyl‐9H‐fluoren‐2‐yl)‐9,9‐dimethyl‐9,10‐dihydroacridine as a core and 1,3‐ and/or 1,4‐phenylene‐linked triphenylimidazole (TPI) analogues for non‐doped solution‐processable OLEDs. Their thermal, photophysical, electrochemical, and device characteristics are explored, and also strongly supported by density functional theory (DFT) study. AFpTPI and AFmTPI exhibit excellent thermal stability (≈450 °C) with high glass transition temperatures (T_g; 141–152 °C) and deep‐blue emission with high quantum yields. Specifically, the solution‐processed non‐doped device with AFpTPI as an emitter exhibits a maximum external quantum efficiency (EQE) of 4.56 % with CIE coordinates of (0.15, 0.06), which exactly matches the European Broadcasting Union (EBU) blue standard. In addition, AFmTPI also displays good efficiency and better color purity (EQE: 3.37 %; CIE (0.15, 0.05)). To the best of our knowledge, the present work is the first report on non‐doped solution‐processable OLEDs with efficiency close to 5 % and CIE y≤0.06.     

Highlights on the Road towards Highly Emitting Solid‐State Luminophores: Two Classes of Thiazole‐Based Organoboron Fluorophores with the AIEE/AIE Effect

Developing a novel, small‐sized molecular building block that may be capable of emitting light in the solid state is a challenging task and has rarely been reported in the literature. BF₂‐containing dyes seem to be promising candidates towards this aim. Two series of new N^NBF₂ complexes showing aggregation‐induced emission (AIE) and aggregation‐induced emission enhancement (AIEE) were designed and synthesized by means of a new protocol, which improved on the traditional method by employing microwave irradiation. The optical and photophysical properties of the BF₂ complexes were investigated in depth. The synthesized complexes showed fluorescence in both solution and the solid state and, in a mixture of tetrahydrofuran/water, may aggregate into fluorescent nanoparticles. The experimental investigation was supported by quantum mechanical calculations. Their availability, stability, large Stokes shifts, and aggregation capabilities, along with their solid‐state emission capability, render this new class of BF₂ complexes promising AIEE/AIE fluorophores for further applications in the fields of fluorescence imaging and materials science.     

Efficient NIR‐Light Emission from Solid‐State Complexes of Boron Difluoride with 2′‐Hydroxychalcone Derivatives

This article describes a series of nine complexes of boron difluoride with 2′‐hydroxychacone derivatives. These dyes were synthesized very simply and exhibited intense NIR emission in the solid state. Complexation with boron was shown to impart very strong donor–acceptor character into the excited state of these dyes, which further shifted their emission towards the NIR region (up to 855 nm for dye 5 b , which contained the strongly donating triphenylamine group). Strikingly, these optical features were obtained for crystalline solids, which are characterized by high molecular order and tight packing, two features that are conventionally believed to be detrimental to luminescence in organic crystals. Remarkably, the emission of light from the π‐stacked molecules did not occur at the expense of the emission quantum yield. Indeed, in the case of pyrene‐containing dye 4 , for example, a fluorescence quantum yield of about 15 % with a fluorescence emission maximum at 755 nm were obtained in the solid state. Moreover, dye 3 a and acetonaphthone‐based compounds 1 b , 2 b , and 3 b showed no evidence of degradation as solutions in CH₂Cl₂ that contained EtOH. In particular, solutions of brightly fluorescent compound 3 a (brightness: ε×Φ_f=45 000 M ^?1 cm^?1) could be stored for long periods without any detectable changes in its optical properties. All together, these new dyes possess a set of very interesting properties that make them promising solid‐state NIR fluorophores for applications in materials science.     

Systematic Investigation of Molecular Arrangements and Solid‐State Fluorescence Properties on Salts of Anthracene‐2,6‐disulfonic Acid with Aliphatic Primary Amines

Organic salts of anthracene‐2,6‐disulfonic acid (ADS) with a wide variety of primary amines have been fabricated, and their arrangements of anthracene molecules and solid‐state fluorescence properties investigated. Single‐crystal X‐ray studies reveal that the salts show seven types of crystal forms and corresponding molecular arrangements of anthracene moieties depending on the amine, while anthracene shows only one form and arrangement in the solid state. Depending on the molecular arrangements, the ADS salts exhibit various solid‐state fluorescence properties: spectral shift (30 nm) and suppression and enhancement of the fluorescence intensity. Especially the ADS salt with n‐heptylamine (nHepA), which shows discrete anthracene moieties in the crystal, exhibits the highest quantum yield (Φ_F=46.1±0.2 %) in the series of ADS salts, which exceeds that of anthracene crystal (Φ_F=42.9±0.2 %). From these systematic investigations on the arrangements and the solid‐state properties, the following factors are essential for high fluorescence quantum yield in the solid state: prevention of contact between π planes of anthracene moieties and immobilization of anthracene rings. In addition, such organic salts have potential as a system for modulating the molecular arrangements of fluorophores and the concomitant solid‐state properties. Thus, systematic investigation of this system constructs a library of arrangements and properties, and the library leads to remarkable strategies for the development of organic solid materials.     

High‐Performance Blue OLEDs Based on Phenanthroimidazole Emitters via Substitutions at the C6‐ and C9‐Positions for Improving Exciton Utilization

Donor–acceptor (D–A) molecular architecture has been shown to be an effective strategy for obtaining high‐performance electroluminescent materials. In this work, two D–A molecules, Ph‐BPA‐BPI and Py‐BPA‐BPI, have been synthesized by attaching highly fluorescent phenanthrene or pyrene groups to the C6‐ and C9‐positions of a locally excited‐state emitting phenylamine–phenanthroimidazole moiety. Equipped with good physical and hybridized local and charge‐transfer properties, both molecules show high performances as blue emitters in nondoped organic light‐emitting devices (OLEDs). An OLED using Ph‐BPA‐BPI as the emitting layer exhibits deep‐blue emission with CIE coordinates of (0.15, 0.08), and a maximum external quantum efficiency (EQE), current efficiency (CE), and power efficiency (PE) of 4.56 %, 3.60 cd A^?1, and 3.66 lm W^?1, respectively. On the other hand, a Py‐BPA‐BPI‐based, sky‐blue OLED delivers the best results among nondoped OLEDs with CIE_y values of < 0.3 reported so far, for which a very low turn‐on voltage of 2.15 V, CIE coordinates of (0.17, 0.29), and maximum CE, PE, and EQE values of 10.9 cd A^?1, 10.5 lm W^?1, and 5.64 %, were achieved, respectively. More importantly, both devices show little or even no efficiency roll‐off and high singlet exciton‐utilizing efficiencies of 36.2 % for Ph‐BPA‐BPI and 39.2 % for Py‐BPA‐BPI.     

Red/Near‐Infrared Thermally Activated Delayed Fluorescence OLEDs with Near 100 % Internal Quantum Efficiency

Developing red thermally activated delayed fluorescence (TADF) emitters, attainable for both high‐efficient red organic light‐emitting diodes (OLEDs) and non‐doped deep red/near‐infrared (NIR) OLEDs, is challenging. Now, two red emitters, BPPZ‐PXZ and mDPBPZ‐PXZ, with twisted donor–acceptor structures were designed and synthesized to study molecular design strategies of high‐efficiency red TADF emitters. BPPZ‐PXZ employs the strictest molecular restrictions to suppress energy loss and realizes red emission with a photoluminescence quantum yield (Φ_PL) of 100±0.8 % and external quantum efficiency (EQE) of 25.2 % in a doped OLED. Its non‐doped OLED has an EQE of 2.5 % owing to unavoidable intermolecular π–π interactions. mDPBPZ‐PXZ releases two pyridine substituents from its fused acceptor moiety. Although mDPBPZ‐PXZ realizes a lower EQE of 21.7 % in the doped OLED, its non‐doped device shows a superior EQE of 5.2 % with a deep red/NIR emission at peak of 680 nm.     

2,5‐Difluorenyl‐Substituted Siloles for the Fabrication of High‐Performance Yellow Organic Light‐Emitting Diodes

2,3,4,5‐Tetraarylsiloles are a class of important luminogenic materials with efficient solid‐state emission and excellent electron‐transport capacity. However, those exhibiting outstanding electroluminescence properties are still rare. In this work, bulky 9,9‐dimethylfluorenyl, 9,9‐diphenylfluorenyl, and 9,9′‐spirobifluorenyl substituents were introduced into the 2,5‐positions of silole rings. The resulting 2,5‐difluorenyl‐substituted siloles are thermally stable and have low‐lying LUMO energy levels. Crystallographic analysis revealed that intramolecular π–π interactions are prone to form between 9,9′‐spirobifluorene units and phenyl rings at the 3,4‐positions of the silole ring. In the solution state, these new siloles show weak blue and green emission bands, arising from the fluorenyl groups and silole rings with a certain extension of π conjugation, respectively. With increasing substituent volume, intramolecular rotation is decreased, and thus the emissions of the present siloles gradually improved and they showed higher fluorescence quantum yields (Φ_F=2.5–5.4 %) than 2,3,4,5‐tetraphenylsiloles. They are highly emissive in solid films, with dominant green to yellow emissions and good solid‐state Φ_F values (75–88 %). Efficient organic light‐emitting diodes were fabricated by adopting them as host emitters and gave high luminance, current efficiency, and power efficiency of up to 44 100 cd m^?2, 18.3 cd A^?1, and 15.7 lm W^?1, respectively. Notably, a maximum external quantum efficiency of 5.5 % was achieved in an optimized device.     

Luminescent Tungsten(VI) Complexes: Photophysics and Applicability to Organic Light‐Emitting Diodes and Photocatalysis

The synthesis, excited‐state dynamics, and applications of two series of air‐stable luminescent tungsten(VI) complexes are described. These tungsten(VI) complexes show phosphorescence in the solid state and in solutions with emission quantum yields up to 22 % in thin film (5 % in mCP) at room temperature. Complex 2 c , containing a 5,7‐diphenyl‐8‐hydroxyquinolinate ligand, displays prompt fluorescence (blue–green) and phosphorescence (red) of comparable intensity, which could be used for ratiometric luminescent sensing. Solution‐processed organic light‐emitting diodes (OLEDs) based on 1 d showed a stable yellow emission with an external quantum efficiency (EQE) and luminance up to 4.79 % and 1400 cd m⁻² respectively. These tungsten(VI) complexes were also applied in light‐induced aerobic oxidation reactions.     

Benzimidazobenzothiazole‐Based Bipolar Hosts to Harvest Nearly All of the Excitons from Blue Delayed Fluorescence and Phosphorescent Organic Light‐Emitting Diodes

Much effort has been devoted to developing highly efficient organic light‐emitting diodes (OLEDs) that function through phosphorescence or thermally activated delayed fluorescence (TADF). However, efficient host materials for blue TADF and phosphorescent guest emitters are limited because of their requirement of high triplet energy levels. Herein, we report the rigid acceptor unit benzimidazobenzothiazole (BID‐BT), which is suitable for use in bipolar hosts in blue OLEDs. The designed host materials, based on BID‐BT, possess high triplet energy and bipolar carrier transport ability. Both blue TADF and phosphorescent OLEDs containing BID‐BT‐based derivatives exhibit external quantum efficiencies as high as 20 %, indicating that these hosts allow efficient triplet exciton confinement appropriate for blue TADF and phosphorescent guest emitters.     

Induction of Strong Long‐Lived Room‐Temperature Phosphorescence of N‐Phenyl‐2‐naphthylamine Molecules by Confinement in a Crystalline Dibromobiphenyl Matrix

The design and preparation of metal‐free organic materials that exhibit room‐temperature phosphorescence (RTP) is a very attractive topic owing to potential applications in organic optoelectronic devices. Herein, we present a facile approach to efficient and long‐lived organic RTP involving the doping of N‐phenylnaphthalen‐2‐amine (PNA) or its derivatives into a crystalline 4,4′‐dibromobiphenyl (DBBP) matrix. The resulting materials showed strong and persistent RTP emission with a quantum efficiency of approximately 20 % and a lifetime of a few to more than 100 milliseconds. Bright white dual emission containing blue fluorescence and yellowish‐green RTP from the PNA‐doped DBBP crystals was also confirmed by Commission Internationale de l'Eclairage (CIE) coordinates of (x=0.29–0.31, y=0.38–0.41).     

Four‐Coordinate Boron Emitters with Tridentate Chelating Ligand for Efficient and Stable Thermally Activated Delayed Fluorescence Organic Light‐Emitting Devices

A new class of four‐coordinate donor‐acceptor fluoroboron‐containing thermally activated delayed fluorescence (TADF) compounds bearing a tridentate 2,2′‐(pyridine‐2,6‐diyl)diphenolate (dppy) ligand has been successfully designed and synthesized. Upon varying the donor moieties from carbazole to 10H‐spiro[acridine‐9,9′‐fluorene] to 9,9‐dimethyl‐9,10‐dihydroacridine, these boron derivatives exhibit a wide range of emission colors spanning from blue to yellow with a large spectral shift of 2746 cm^?1, with high PLQYs of up to 96 % in the doped thin film. Notably, vacuum‐deposited organic light‐emitting devices (OLEDs) made with these boron compounds demonstrate high performances with the best current efficiencies of 55.7 cd A^?1, power efficiencies of 58.4 lm W^?1 and external quantum efficiencies of 18.0 %. More importantly, long operational stabilities of the green‐emitting OLEDs based on 2 with half‐lifetimes of up to 12 733 hours at an initial luminance of 100 cd m^?2 have been realized. This work represents for the first time the design and synthesis of tridentate dppy‐chelating four‐coordinate boron TADF compounds for long operational stabilities, suggesting great promises for the development of stable boron‐containing TADF emitters.     

Luminescent Platinum(II) Complexes of 1,3‐Bis(N‐alkylbenzimidazol‐ 2′‐yl)benzene‐Type Ligands with Potential Applications in Efficient Organic Light‐Emitting Diodes

A series of luminescent platinum(II) complexes of tridentate 1,3‐bis(N‐alkylbenzimidazol‐2′‐yl)benzene (bzimb) ligands has been synthesized and characterized. One of these platinum(II) complexes has been structurally characterized by X‐ray crystallography. Their electrochemical, electronic absorption, and luminescence properties have been investigated. Computational studies have been performed on this class of complexes to elucidate the origin of their photophysical properties. Some of these complexes have been utilized in the fabrication of organic light‐emitting diodes (OLEDs) by using either vapor deposition or spin‐coating techniques. Chloroplatinum(II)? bzimb complexes that are functionalized at the 5‐position of the aryl ring, [Pt(R‐bzimb)Cl], not only show tunable emission color but also exhibit high current and external quantum efficiencies in OLEDs. Concentration‐dependent dual‐emissive behavior was observed in multilayer OLEDs upon the incorporation of pyrenyl ligand into the Pt(bzimb) system. Devices doped with low concentrations of the complexes gave rise to white‐light emission, thereby representing a unique class of small‐molecule, platinum(II)‐based white OLEDs.     

Non‐Doped Sky‐Blue OLEDs Based on Simple Structured AIE Emitters with High Efficiencies at Low Driven Voltages

Blue organic light‐emitting diodes (OLEDs) are necessary for flat‐panel display technologies and lighting applications. To make more energy‐saving, low‐cost and long‐lasting OLEDs, efficient materials as well as simple structured devices are in high demand. However, a very limited number of blue OLEDs achieving high stability and color purity have been reported. Herein, three new sky‐blue emitters, 1,4,5‐triphenyl‐2‐(4‐(1,2,2‐triphenylvinyl)phenyl)‐1H‐imidazole (TPEI), 1‐(4‐methoxyphenyl)‐4,5‐diphenyl‐2‐(4‐(1,2,2‐triphenylvinyl)phenyl)‐1H‐imidazole (TPEMeOPhI) and 1‐phenyl‐2,4,5‐tris(4‐(1,2,2‐triphenylvinyl)phenyl)‐1H‐imidazole (3TPEI), with a combination of imidazole and tetraphenylethene groups, have been developed. High photoluminescence quantum yields are obtained for these materials. All derivatives have demonstrated aggregation‐induced emission (AIE) behavior, excellent thermal stability with high decomposition and glass transition temperatures. Non‐doped sky‐blue OLEDs with simple structure have been fabricated employing these materials as emitters and realized high efficiencies of 2.41 % (4.92 cd A⁻¹, 2.70 lm W⁻¹), 2.16 (4.33 cd A⁻¹, 2.59 lm W⁻¹) and 3.13 % (6.97 cd A⁻¹, 4.74 lm W⁻¹) for TPEI, TPEMeOPhI and 3TPEI, with small efficiency roll‐off. These are among excellent results for molecules constructed from the combination of imidazole and TPE reported so far. The high performance of a 3TPEI‐based device shows the promising potential of the combination of imidazole and AIEgen for synthesizing efficient electroluminescent materials for OLED devices.