Versatile Functionalization of the Micropatterned Hydrogel of Hyperbranched Poly(ether amine) Based on “Thiol‐yne” Chemistry

The functionalization of a hydrogel with target molecules is one of the key steps in its various applications. Here, a versatile approach is demonstrated to functionalize a micropatterned hydrogel, which is formed by “thiol‐yne” photo‐click reaction between the yne‐ended hyperbranched poly(ether amine) (hPEA‐yne) and thiol‐containing polyhedral oligomeric silsesquioxane (PEG‐POSS‐SH). By controlling the molar ratio between hPEA‐yne and PEG‐POSS‐SH, patterned hydrogels containing thiol or yne groups are obtained. A series of thiol‐based click chemistry such as “thiol‐epoxy”, “thiol‐halogen”, “thiol‐ene”, and “thiol‐isocyanate” are used to functionalize the thiol‐containing hydrogel (Gel‐1), while the yne‐containing hydrogel (Gel‐2) is functionalized through a typical copper‐catalysed alkyne‐azide reaction (CuAAC). FTIR, UV‐vis spectra and confocal laser scanning microscopy (CLSM) are used to trace these click reactions. Due to the selective adsorption to the hydrophilic dyes, the obtained patterned hydrogel of hPEA modified with fluorescence dye is further demonstrated in application for the recognition of guest molecules.     

Origin of the Exclusive Ternary Electroluminescent Behavior of BN‐Doped Nanographenes in Efficient Single‐Component White Light‐Emitting Electrochemical Cells

White‐light‐emitting electrochemical cells (WLECs) still represent a significant milestone, since only a few examples with moderate performances have been reported. Particularly, multiemissive white emitters are highly desired, as a paradigm to circumvent phase separation and voltage‐dependent emission color issues that are encountered following host:guest and multilayered approaches. Herein, the origin of the exclusive white ternary electroluminescent behavior of BN‐doped nanographenes with a B₃N₃ doping pattern (hexa‐perihexabenzoborazinocoronene) is rationalized, leading to one of the most efficient (≈3 cd A^?1) and stable‐over‐days single‐component and single‐layered WLECs. To date, BN‐doped nanographenes have featured blue thermally activated delayed fluorescence (TADF). This doping pattern provides, however, white electroluminescence spanning the whole visible range (x/y CIE coordinates of 0.29–31/0.31–38 and average color rendering index (CRI) of 87) through a ternary emission involving fluorescence and thermally activated dual phosphorescence. This temperature‐dependent multiemissive mechanism is operative for both photo‐ and electroluminescence processes and holds over the device lifespan, regardless of the device architecture, active layer composition, and operating conditions. As such, this work represents a new stepping‐stone toward designing a new family of multiemissive white emitters based on BN‐doped nanographenes that realizes one of the best‐performing single‐component white‐emitting devices compared to the prior‐art.     

Doping‐Induced Charge Trapping in Organic Light‐Emitting Devices

By using pyran‐containing donor–acceptor dyes as doping molecules in organic light‐emitting devices (OLEDs), we scrutinize the effects of charge trapping and polarization induced by the guest molecules in the electro‐active host material. Laser dyes 4‐(dicyanomethylene)‐2‐methyl‐6‐[2‐(julolidin‐9‐yl)phenyl]ethenyl]‐4H‐pyran (DCM2) and the novel 4‐(dicyanomethylene)‐2‐methyl‐6‐{2‐[(4‐diphenylamino)phenyl]ethenyl}‐4H‐pyran (DCM‐TPA) are used as model compounds. The emission color of these polar dyes depends strongly on doping concentration, which we have attributed to polarization effects induced by the doping molecules themselves. Their frontier orbital energy levels are situated within the bandgap of the tris(8‐hydroxyquinoline)aluminum (Alq₃) host matrix and allow the investigation of either electron trapping or both electron and hole trapping. In the case of DCM‐TPA doping, we were able to show that electron trapping leads to a partial shift of the recombination zone out of the doped Alq₃ region. To impede charge‐recombination processes taking place in the undoped host matrix, a charge‐blocking layer efficiently confines the recombination zone inside the doped zone and gives rise to increased luminous efficiency. For a doping concentration of 1 wt.‐% we obtain a maximum luminous efficiency of 10.4 cd A^–1. At this doping concentration, the yellow emission spectrum shows excellent color saturation with CIE chromaticity coordinates x, y of 0.49 and 0.50, respectively. In the case of DCM2 the recombination zone is much less affected for the same doping concentrations, which is ascribed to the fact that both electrons and holes are being trapped. The experimental findings are corroborated with a numerical simulation of the doped multilayer devices.     

Photoinduced Tetrazole‐Based Functionalization of Off‐Stoichiometric Clickable Microparticles

We report the preparation of tetrazole‐containing step‐growth microparticles and the subsequent use of photoinduced nitrile imine‐mediated tetrazole‐ene cycloaddition (NITEC) reactions on the particles with spatiotemporal control. Microparticles with an average diameter of 4.1 µm and with inherent tetrazole‐ene dual functionality are prepared by a one‐pot off‐stoichiometric thiol‐Michael addition dispersion polymerization. The NITEC reaction is performed efficiently in the solid phase by UV irradiation, leading to the formation of fluorescent pyrozoline adducts, with an estimated quantum yield of 0.7. Particle concentration‐independent reaction kinetics are observed and full conversion is reached within 10 min of UV exposure at an intensity of 8 mW cm^?2. Temporal control is demonstrated with either UV or rooftop sunlight irradiation of variable duration. By using two‐photon writing with a laser centered around 700 nm wavelength, spatial control is demonstrated with micrometer‐scale resolution via surface patterning of the microparticles. Further, microparticles with exclusive tetrazole functionality are prepared by a one‐pot, two‐step thiol‐Michael addition dispersion polymerization. The NITEC reaction between tetrazole‐functional particles and acrylates in solution is examined at various tetrazole/alkene molar ratios, and a 10:1 excess of alkenes in solution is found necessary for efficient functionalization.     

Electrochromic Polymer‐Dispersed Liquid‐Crystal Film: A New Bifunctional Device

Polymer‐dispersed liquid crystals (PDLCs) are liquid‐crystal dispersions within a polymer matrix. These films can be changed from an opaque to a transparent state by applying a suitable alternating‐current electric field. PDLCs have attracted the interest of researchers for their applications as light shutters, smart windows, and active displays. For such applications, electrochromic devices, which change color as a result of electrochemical reactions, have also become a recent focus of research. Herein, we report our preliminary results on bifunctional devices based on PDLCs that host electrochromic guest molecules. Such devices allow both an independent and fast switching from a scattering opaque state to a transmissive transparent state owing to liquid‐crystal reorientation and a color change from white (pale yellow) to dark blue, due to either oxidation or reduction of the electrochromic molecules.     

1 + 1 >> 2: Dramatically Enhancing the Emission Efficiency of TPE‐Based AIEgens but Keeping their Emission Color through Tailored Alkyl Linkages

Currently, the development of aggregation‐induced emission (AIE) luminogens (AIEgens) has enabled us to “see” never before seen scenery. However, not all AIEgens exhibit the impressive emission efficiency in aggregated states. Moreover, the emission color of AIEgens can be seriously affected when their performance is improved. Therefore, to overcome this limitation, an efficient method is proposed here through the tailored alkyl linkages to greatly improve the emission efficiency of tetraphenylethene (TPE)‐based AIEgens but retain their emission color. Encouragingly, significantly enhanced emission efficiency is achieved with the quantum yield up to 68.19% and 65.20% for BTPE‐C4 and BTPE‐C8, respectively, in contrast to that of TPE (25.32%), demonstrating the proverb that one plus one is much larger than two (1 + 1 >> 2). Interestingly, when alkyl linkages in skeletons are fine‐tuned, self‐assembled nanorods, nanosheets, and nanofibers are successfully achieved for BTPE‐C1, BTPE‐C4, and BTPE‐C8 in tetrahydrofuran and water system. Also, these developed emissive AIEgens not only exhibit impressive response to the environmental stimuli of mechanical force, viscosity, temperature, and light, but can also be used to dynamically monitor and control the phase‐separated morphology in polymeric blends.     

Tuning the Emitting Color of Organic Light‐Emitting Diodes Through Photochemically Induced Transformations: Towards Single‐Layer,Patterned, Full‐Color Displays and White‐Lighting Applications

Photochemically induced emission tuning for the definition of pixels emitting the three primary colors, red, green, blue (RGB), in a single conducting polymeric layer is investigated. The approach proposed is based on an acid‐induced emission shift of the (1‐[4‐(dimethylamino)phenyl]‐6‐phenylhexatriene) (DMA‐DPH) green emitter and acid‐induced quenching of the red fluorescent emitter (4‐dimethylamino‐4′‐nitrostilbene) (DANS). The two emitters are dispersed in the wide bandgap conducting polymer poly(9‐vinylcarbazole) (PVK), along with a photoacid generator (PAG). In the unexposed film areas, red emission is observed because of efficient energy transfer from PVK and DMA‐DPH to DANS. Exposure of selected areas of the film at different doses results in quenching of the red emitter's fluorescence and the formation of green, blue, or even other color‐emitting pixels, depending on the exposure dose and the relative concentrations of the different compounds in the film. Organic light‐emitting diodes having the PVK polymer containing the appropriate amounts of DMA‐DPH, DANS, and PAG as the emitting layer are fabricated and electroluminescence spectra are recorded. The time stability of induced emission spectrum changes and the color stability during device operation are also examined, and the first encouraging results are obtained.     

Intercalation‐Induced Tunable Stimuli‐Responsive Color‐Change Properties of Crystalline Organic Layered Compound

Layered structures accommodate guest molecules and ions in the interlayer space through intercalation. Organic layered compounds, such as layered polymers, have both intercalation and dynamic properties. Here intercalation‐induced tunable temperature‐ and mechanical‐stress‐responsive color‐change properties of crystalline layered polydiacetylene (PDA) as an organic layered compound are reported. In general, organic materials with stimuli responsivity are developed by molecular design and synthesis. In the present work, intercalation of guest metal cations in the layered PDA directs tuning of the stimuli‐responsive color‐change properties, such as color, responsivity, and reversibility. Whereas PDA without intercalation of metal ions distinctly changes the color from blue to red at the threshold temperature, the PDA with intercalation of the divalent metal ions (PDA‐M²⁺) shows a variety of color‐change properties. The present study indicates that intercalation has versatile potentials for functionalization of organic layered compounds.     

Molecularly‐Engineered, 4D‐Printed Liquid Crystal Elastomer Actuators

Three‐dimensional structures that undergo reversible shape changes in response to mild stimuli enable a wide range of smart devices, such as soft robots or implantable medical devices. Herein, a dual thiol‐ene reaction scheme is used to synthesize a class of liquid crystal (LC) elastomers that can be 3D printed into complex shapes and subsequently undergo controlled shape change. Through controlling the phase transition temperature of polymerizable LC inks, morphing 3D structures with tunable actuation temperature (28 ± 2 to 105 ± 1 °C) are fabricated. Finally, multiple LC inks are 3D printed into single structures to allow for the production of untethered, thermo‐responsive structures that sequentially and reversibly undergo multiple shape changes.     

Controlling the Chromaticity of Small‐Molecule Light‐Emitting Electrochemical Cells Based on TIPS‐Pentacene

This work demonstrates a novel proof‐of‐concept to implement pentacene derivatives as emitters for the third generation of light‐emitting electrochemical cells based on small‐molecules (SM‐LECs). Here, a straightforward procedure is shown to control the chromaticity of pentacene‐based lighting devices by means of a photoinduced cycloaddition process of the 6,13‐bis(triisopropylsilylethynyl) (TIPS)‐pentacene that leads to the formation of anthracene‐core dimeric species featuring a high‐energy emission. Without using the procedure, SM‐LECs featuring deep‐red emission with Commission Internationale d'Eclairage (CIE) coordinates of x = 0.69/y = 0.31 and irradiance of 0.4 μW cm^?2 are achieved. After a careful optimization of the cycloaddition process, warm white devices with CIE coordinates of x = 0.36/y = 0.38 and luminances of 10 cd m^?2 are realized. Here, the mechanism of the device is explained as a host–guest system, in which the dimeric species acts as the high‐energy band gap host and the low‐energy bandgap TIPS‐pentacene is the guest. To the best of the knowledge, this work shows the first warm white SM‐LECs. Since this work is based on the archetypal TIPS‐pentacene and the photoinduced cycloaddition process is well‐knownfor any pentacenes, this proof‐of‐concept could open a new way to use these compounds for developing white lighting sources.     

A Green Polymeric Light‐Emitting Diode Material: Poly(9,9‐dioctylfluorene‐alt‐thiophene) End‐Capped with Gold Nanoparticles

Poly(9,9‐dioctylfluorene‐alt‐thiophene copolymer (PDOFT) is functionalized with thiol and end‐capped with in‐situ‐reduced gold nanoparticles (AuNPs). The molecular structure of the resulting material (PDOFT‐Au) is corroborated by ¹H and ¹³C NMR spectroscopy, and direct evidence for the binding between the PDOFT‐bis‐4‐thiol and gold nanoparticles is provided from X‐ray photoelectron spectroscopy. PDOFT‐Au is not only soluble in common organic solvents, but also has a broad range of thermal stability, up to 414 °C. The photoluminescence and electroluminescence spectra show that excitation of PDOFT is virtually unaffected by the end‐capping with gold nanoparticles. However, atomic force microscopy shows that the root‐mean‐square roughness of the PDOFT‐Au film is nearly ten times higher than that of the PDOFT film, resulting in an increased interfacial area between the film and the deposited cathode in a PDOFT‐Au device. This increased interfacial area, together with the photo‐oxidation‐suppressing and hole‐blocking characteristics of AuNPs, significantly enhances the electron injection, lowers the threshold voltage, and increases the electroluminescence (10 521 cd m^–2) and photometric efficiency (1.986 cd A^–1) of the PDOFT‐Au device by nearly an order of magnitude. These increases in electroluminescence and photometric efficiency would be much lower if AuNPs were blended into—rather than capped onto—the copolymer. The Commission International de L'Eclairage color coordinates of PDOFT‐Au (0.237,0.655) are very close to the standard green demanded by the National Television System Committee, making PDOFT‐Au an excellent candidate for a green‐light‐emitting material.     

High‐Efficiency and Color Stable Blue‐Light‐Emitting Polymers and Devices

Novel fluorene‐based blue‐light‐emitting copolymers with an ultraviolet‐blue‐light (UV‐blue‐light) emitting host and a blue‐light emitting component, 4‐N,N‐diphenylaminostilbene (DPS) have been designed and synthesized by using the palladium‐ catalyzed Suzuki coupling reaction. It was found that both copolymers poly [2,7‐(9,9‐dioctylfluorene)‐alt‐1,3‐(5‐carbazolphenylene)] (PFCz) DPS1 and PFCz‐DPS1‐OXD show pure blue‐light emission even with only 1 % DPS units because of the efficient energy transfer from the UV‐blue‐light emitting PFCz segments to the blue‐light‐emitting DPS units. Moreover, because of the efficient energy transfer/charge trapping in these copolymers, PFCz‐DPS1 and PFCz‐DPS1‐OXD show excellent device performance with a very stable pure blue‐light emission. By using a neutral surfactant poly[9,9‐bis(6'‐(diethanolamino)hexyl)‐fluorene] (PFN‐OH) as the electron injection layer, the device based on PFCz‐DPS1‐OXD5 with the configuration of ITO/PEDOT:PSS/PVK/polymer/PFN‐OH/Al showed a maximum quantum efficiency of 2.83 % and a maximum luminous efficiency of 2.50 cd A^–1. Its CIE 1931 chromaticity coordinates of (0.156, 0.080) match very well with the NTSC standard blue pixel coordinates of (0.14, 0.08). These results indicate that this kind of dopant/host copolymer could be a promising candidate for blue‐light‐emitting polymers with high efficiency, good color purity, and excellent color stability.     

Host Exciton Confinement for Enhanced Förster‐Transfer‐Blend Gain Media Yielding Highly Efficient Yellow‐Green Lasers

This paper reports state‐of‐the‐art fluorene‐based yellow‐green conjugated polymer blend gain media using Förster resonant‐energy‐transfer from novel blue‐emitting hosts to yield low threshold (≤7 kW cm^?2) lasers operating between 540 and 590 nm. For poly(9,9‐dioctylfluorene‐co‐benzothiadiazole) (F8BT) (15 wt%) blended with the newly synthesized 3,6‐bis(2,7‐di([1,1′‐biphenyl]‐4‐yl)‐9‐phenyl‐9H‐fluoren‐9‐yl)‐9‐octyl‐9H–carbazole (DBPhFCz) a highly desirable more than four times increase (relative to F8BT) in net optical gain to 90 cm^?1 and 34 times reduction in amplified spontaneous emission threshold to 3 µJ cm^?2 is achieved. Detailed transient absorption studies confirm effective exciton confinement with consequent diffusion‐limited polaron‐pair generation for DBPhFCz. This delays formation of host photoinduced absorption long enough to enable build‐up of the spectrally overlapped, guest optical gain, and resolves a longstanding issue for conjugated polymer photonics. The comprehensive study further establishes that limiting host conjugation length is a key factor therein, with 9,9‐dialkylfluorene trimers also suitable hosts for F8BT but not pentamers, heptamers, or polymers. It is additionally demonstrated that the host highest occupied and lowest unoccupied molecular orbitals can be tuned independently from the guest gain properties. This provides the tantalizing prospect of enhanced electron and hole injection and transport without endangering efficient optical gain; a scenario of great interest for electrically pumped amplifiers and lasers.     

Recent Progress in White Light‐Emitting Electrochemical Cells

Solid‐state white light‐emitting electrochemical cells (LECs) exhibit the following advantages: simple device structures, low operation voltage, and compatibility with inert metal electrodes. LECs have been studied extensively since the first demonstration of white LECs in 1997, due to their potential application in solid‐state lighting. This review provides an overview of recent developments in white LECs, specifically three major aspects thereof, namely, host–guest white LECs, nondoped white LECs, and device engineering of white LECs. Host–guest strategy is widely used in white LECs. Host materials are classified into ionic transition metal complexes, conjugated polymers, and small molecules. Nondoped white LECs are based on intra‐ or intermolecular interactions of emissive and multichromophore materials. New device engineering techniques, such as modifying carrier balance, color downconversion, optical filtering based on microcavity effect and localized surface plasmon resonance, light extraction enhancement, adjusting correlated color temperature of the output electroluminescence spectrum, tandem and/or hybrid devices combining LECs with organic light‐emitting diodes, and quantum‐dot light‐emitting diodes improve the device performance of white LECs by ways other than material‐oriented approaches. Considering the results of the reviewed studies, white LECs have a bright outlook.     

Very High Efficiency Orange‐Red Light‐Emitting Devices with Low Roll‐Off at High Luminance Based on an Ideal Host–Guest System Consisting of Two Novel Phosphorescent Iridium Complexes with Bipolar Transport

Two phosphorescent iridium complexes with bipolar transporting ability, namely FPPCA (500 nm) and BZQPG (600 nm), are synthesized and employed as an ideal host‐guest system for phosphorescent organic light emitting diodes (PHOLEDs).The devices give very high‐efficiency orange‐red emission from BZQPG with maximum external quantum efficiency (EQE or η_ext) of >27% and maximum power efficiency (PE or η_p) of >75 lm/W, and maintain high levels of 26% and 55 lm/W, 25% and 40 lm/W at high luminance of 1000 and 5000 cd m^?2, respectively, within a range of 8–15 wt% of BZQPG. The realization of such high and stable EL performance results from the coexistence of two parallel paths: i) effective energy transfer from host (FPPCA) to guest (BZQPG) and ii) direct exciton formation on the BZQPG emitter, which can alternately dominate the electrophosphorescent emission. This all‐phosphor doping system removes the charge‐injection barrier from the charge‐transport process to the emissive layer (EML) due to the inherent narrow E_g of both phosphors. Therefore, this ideal host–guest system represents a new design to produce PHOLEDs with high efficiency and low efficiency roll‐off using a simple device configuration.     

Highly Efficient Multifunctional Supramolecular Gene Carrier System Self‐Assembled from Redox‐Sensitive and Zwitterionic Polymer Blocks

It has been a challenge to incorporate multiple features into a single gene carrier system to overcome numerous hurdles during the gene delivery. Herein, a supramolecular approach for building a multifunctional gene carrier system is demonstrated with the functions of disulfide bond based reduction‐responsive degradation and zwitterionic phosphorylcholine based extracellular stabilization and favorable cellular uptake. The gene carrier system is self‐assembled from two molecular building blocks: one host polymer, which is a redox‐sensitive β‐cyclodextrin based cationic star polymer, and one guest polymer, which is adamantyl end capped zwitterionic phosphorylcholine based polymer. The host and guest polymers self‐assemble to integrate multiple functions into one system, based on the host‐guest interaction between β‐cyclodextrin and adamantyl moieties. With the rational designs of both building blocks, the supramolecular gene carrier system possesses excellent protein stability, serum tolerance, cellular uptake and intracellular DNA release properties, and also low cytotoxicity. These features work simultaneously to achieve exceptionally high gene transfection efficiency, which is proven in MCF‐7 cell cultures using luciferase and green fluorescence protein reporter genes. Finally, the supramolecular gene carrier is applied to deliver the therapeutic p53 anti‐cancer gene in MCF‐7 cells, showing great potential for cancer gene therapy application.     

Sunlight‐Induced Cross‐Linked Luminescent Films Based on Polysiloxanes and d‐Limonene via Thiol–ene “Click” Chemistry

The increasing pursuit of biocontained elastic materials led the investigation of the potential use of the monoterpene limonene in film synthesis via thiol–ene reaction. Poly[(mercaptopropyl)methylsiloxane] (PMMS) is first synthesized. By controlling the molar ratio of PMMS and functional monomers, such as polyethylene glycol allyl methyl ether or rhodamine‐B, PMMS is partially functionalized while leaving spare mercapto groups that could be further used as cross‐linking sites. On the basis of the functionalized PMMS, novel transparent silicone luminescent films with hydrophilic tunable properties are prepared by natural‐sunlight‐triggered thiol–ene “click” chemistry by using d ‐limonene as a cross‐linker. Their structures and properties are thoroughly characterized. Transparent luminescent films are coated on commercially available UV‐light emitting diode (LED) cell from solution medium followed by an in situ cross‐linking step; a colorful LED cell is obtained through this facile and efficient method. The UV‐LED coated by films show very intense photoluminescence under normal visible light or the light is on, and has very high coloric purity.     

Emission Color Tuning in Ambipolar Organic Single‐Crystal Field‐Effect Transistors by Dye‐Doping

The effect of dye‐doping in ambipolar light‐emitting organic field‐effect transistors (LE‐OFETs) is investigated from the standpoint of the carrier mobilities and the electroluminescence (EL) characteristics under ambipolar operation. Dye‐doping of organic crystals permits not only tuning of the emission color but also significantly increases the efficiency of ambipolar LE‐OFETs. A rather high external EL quantum efficiency (～0.64%) of one order of magnitude higher than that of a pure p‐distyrylbenzene (P3V2) single crystal is obtained by tetracene doping. The doping of tetracene molecules into a host P3V2 crystal has almost no effect on the electron mobility and the dominant carrier recombination process in the tetracene‐doped P3V2 crystal involves direct carrier recombination on the tetracene molecules.     

Control of Electrophosphorescence in Conjugated Dendrimer Light‐Emitting Diodes

We present a novel platinum porphyrin based phosphorescent dendrimer for use as a triplet harvesting dopant in organic light‐emitting diodes. Two types of dendritic host materials are used. Through the choice of a common branching architecture around the emissive chromophore unit of both guest and host materials, we are able to achieve excellent miscibility. The relative contribution of guest to host emission is found to depend strongly on the energy level offsets of the two blend materials, indicating strong trapping processes. Under pulsed operation, we observe a striking dependence of the emission spectrum on pulse period, independent of the host material used. This spectral modification is attributed to the quenching of triplet excitations at high excitation densities. We find excellent agreement between our measured data and a model based on bimolecular recombination.     

A Novel Fluorene‐Triphenylamine Hybrid That is a Highly Efficient Host Material for Blue‐, Green‐, and Red‐Light‐Emitting Electrophosphorescent Devices

TFTPA (tris[4‐(9‐phenylfluoren‐9‐yl)phenyl]amine), a novel host material that contains a triphenylamine core and three 9‐phenyl‐9‐fluorenyl peripheries, was effectively synthesized through a Friedel‐Crafts‐type substitution reaction. Owing to the presence of its sterically bulky 9‐phenyl‐9‐fluorenyl groups, TFTPA exhibits a high glass transition temperature (186 °C) and is morphologically and electrochemically stable. In addition, as demonstrated from atomic force microscopy measurements, the aggregation of the triplet iridium dopant is significantly diminished in the TFTPA host, resulting in a highly efficient full‐color phosphorescence. The performance of TFTPA ‐based devices is far superior to those of the corresponding mCP‐ or CBP‐based devices, particularly in blue‐ and red‐emitting electrophosphorescent device systems. The efficiency of the FIrpic‐based blue‐emitting device reached 12 % (26 cd A^–1) and 18 lm W^–1 at a practical brightness of 100 cd m^–2; the Ir(piq)₂acac‐based red‐emitting device exhibited an extremely low turn‐on voltage (2.6 V) and a threefold enhancement in device efficiency (9.0 lm W^–1) relative to those of reference devices based on the CBP host material.