Practical Luminance Research Articles

Peripheral carbazole units-decorated MR emitter containing B−N covalent bond for highly efficient green OLEDs with low roll-off

Boron−nitrogen doped multiple resonance (BN-MR) emitters, characterized by B−N covalent bonds, offer distinctive advantages as pivotal building blocks for facile access to novel MR emitters featuring narrowband spectra and high efficiency. However, there remains a scarcity of exploration concerning synthetic methods and structural derivations to expand the library of novel BN-MR emitters. Herein, we present the synthesis of a BN-MR emitter, tCz[B−N]N, through a one-pot borylation reaction directed by the amine group, achieving an impressive yield of 94%. The emitter is decorated by incorporating two 3,6-di-t-butylcarbazole (tCz) units into a B−N covalent bond doped BN-MR parent molecule via para-C−π−D and para-N−π−D conjugations. This peripheral decoration strategy enhances the reverse intersystem crossing process and shifts the emission band towards the pure green region, peaking at 526 nm with a narrowband full-width at half maximum (FWHM) of 41 nm. Consequently, organic light emitting diodes (OLEDs) employing this emitter achieved a maximum external quantum efficiency (EQEmax) value of 27.7%, with minimal efficiency roll-off. Even at a practical luminance of 1000 cd∙m−2, the device maintains a high EQE value of 24.6%.

Color-Tunable Organic Light-Emitting Diodes with Single Pt (O^N^C^N)-Dibenzofuran Emitter Exhibiting High External Quantum Efficiency of ≈30% and Superior Operational Lifetime.

Color-tunable organic light-emitting diodes (CT-OLEDs) have a large color-tuning range, high efficiency and operational stability at practical luminance, making them ideal for human-machine interactive terminals of wearable biomedical devices. However, the device operational lifetime of CT-OLEDs is currently far from reaching practical requirements. To address this problem, a tetradentate Pt(II) complex named tetra-Pt-dbf, which can emit efficiently in both monomer and aggregation states, is designed. This emitter has high Td of 508°C and large intermolecular bonding energy of -52.0kcalmol⁻1, which improve its thermal/chemical stability. This unique single-emitter CT-OLED essentially avoids the "color-aging issue" and achieves a large color-tuning span (red to yellowish green) and a high external quantum efficiency （EQE） of ≈30% at 1000cd m-2 as well as an EQE of above 25% at 10000cd m-2. A superior LT90 operational lifetime of 520,536 h at a functional luminance of 100cd m-2, which is over 20 times longer than the state-of-the-art CT-OLEDs, is estimated. To demonstrate the potential application of such OLEDs in wearable biomedical devices, a simple electromyography (EMG)-visualization system is fabricated using the CT-OLEDs.

Highly Efficient Copper(I) Emitters Supported by Secondary Metal‐Ligand Interactions

AbstractThe most prominent way of tuning optoelectronic properties of copper(I) emitters is primary‐sphere ligand engineering, but little attention is placed on noncovalent interactions. Here, an effective strategy is demonstrated to introduce secondary metal‐ligand interactions into two‐coordinate Cu(I) emitters with the goals of optimizing conformations and improving optical properties. As a proof of concept, a panel of Cu(I) complexes is developed via chalcogen‐heterocyclic engineering on the 1,2‐positions of carbazole ligand. The S‐embedded complexes have distinct noncovalent metal‐ligand interactions originating from S···Cu orbital contacts, verified by single‐crystal structure and theoretical simulation. Thanks to the flattened conformations stabilized by secondary metal‐ligand interactions, the optimized Cu(I) emitters afford high emission quantum yields of up to 93% and short radiative lifetimes of down to 0.8 µs. Cu‐12BT and Cu‐12BF support the resultant organic light‐emitting diodes (OLEDs) delivering outstanding maximum external quantum efficiencies (EQEs) of 24.3% and 28.6%, respectively, among the best performance for Cu(I) emitters. The optimal devices based on Cu‐12BF also achieve 18.7% EQE at the practical luminance of 100 nits. This work unlocks the large potential of noncovalent interactions in developing excellent Cu(I) emitters for cost‐effective and high‐efficiency OLEDs.

All-fluorescent white organic light-emitting diodes employing a deep-blue HLCT material simultaneously as emitter and host achieving excellent electroluminescence performance with efficiency roll-off

Simultaneously achieving high efficiency and small efficiency roll-off remains a huge challenge for white organic light-emitting diodes (OLEDs), which greatly restricts their industrial application in the lighting field. Recently developed hybridized local and charge transfer (HLCT) materials have a “hot exciton” channel, which can maximize the utilization rate of excitons and suppress efficiency roll-off via rapid reverse intersystem crossing (RISC) from high-lying triplet state (Tn, n ≥ 2) to singlet state (S1). In this work, employing blue HLCT material pCzAnN as the sensitizing host, by precise concentration management, the traditional fluorescent C545T- and DCJTB-based green and orange-red OLEDs are first fabricated, which achieve the maximum external quantum efficiency (EQE) exceeding the theoretical limit of 5 %, reaching 8.51 % and 6.64 %, respectively. On this basis, by strategic device structure design, all-fluorescent two- and three-color white OLEDs are demonstrated having pCzAnN simultaneously as blue emitter and sensitizing host of C545T and DCJTB. The resulting two- and three-color white devices obtain maximum EQE beyond 5 %. What's more, all three-color white devices exhibit extremely small efficiency roll-off, where the efficiency drops are less than 1 % at a practical luminance of 1000 cd/m2, which is comparable to the best works reported in the literatures. At the same time, the optimized three-color white device realizes ideal white emission, in which the electroluminescence (EL) spectra contain three almost equal intensity emission wavebands accompanied by a high color rendering index of 87. Stable EL spectra under a wide luminance range (3863 ∼ 27710 cd/m2) indicate a huge potential application. We believe this work can provide new idea for developing high-efficiency and low roll-off white OLEDs in the future.

Spirobifluorene-fused strategy enables pure-green multiple resonance emitters with low efficiency roll-off.

Herein, we present a molecular design strategy centered on the spiroannulation of the MR-core skeleton to fabricate green MR-emitters and reduce device efficiency roll-off. Fusing 9,9'-spirobifluorene into the central framework of MR-emitters facilitates the distribution of the highest occupied molecular orbital (HOMO) across the spiro units, leading to a red-shifted emission and giving rise to a pure-green MR-emitter (DPhCz-SFBN) with the Commission Internationale de l'Eclairage (CIE) coordinates of [0.16, 0.74] in toluene solution, closely matching the BT.2020 standard for green. Additionally, the resultant highly twisted hetero[6]helicene conformation and a nearly perpendicular conformation of spirocycle structure effectively minimize close π-π stacking interactions among the MR-emitting cores, thereby reducing exciton quenching. Consequently, organic light-emitting diodes (OLEDs) based on DPhCz-SFBN exhibit a high maximum quantum efficiency (EQEmax) of 32.8% with low efficiency roll-off, maintaining an EQE of 23.2% at a practical luminance level of 5000 cd m-2.

Luminescent carbene-copper(i)-amide polymers for efficient host-free solution-processed OLEDs.

Luminescent metallopolymers have attracted broad interest in the fields of healthcare and organic electronics. However, polymeric emitters based on earth-abundant metal complexes are scarce. Here, two series of Cu(i) polymers, PMAC-x and PCAAC-x (x = 1-3) have been developed using two kinds of Cu(i)-based carbene-metal-amide (CMA) complexes as side-chain emitter units to combine with a nonconjugated polystyrene backbone. These Cu(i) polymers emit via distinct thermally activated delayed fluorescence or dominant phosphorescence, inherited from the grafted Cu(i)-based CMA units. Particularly, the PMAC-x polymers exhibit high photoluminescence quantum efficiencies of up to 0.78, short emission lifetimes of down to 0.66 μs, and fast radiative rates of up to 106 s-1 in neat films. Thanks to the good encapsulation effect of the polystyrene backbone, these Cu(i) polymers not only demonstrate favorable moisture stability but also show significant aggregation-induced emission. The resultant host-free solution-processed organic light-emitting diodes (OLEDs) achieve outstanding electroluminescence performance with a record external quantum efficiency of 13.8% at a practical luminance of ∼100 nits, representing state-of-the-art device efficiency for metallopolymer-based OLEDs. This work not only presents the first example of CMA polymers but also provides the future direction of polymeric emitters from earth-abundant metal complexes for the OLED application.

New bipolar derivatives with diphenylsulfone or dibenzophenone as TADF based emitters for OLEDs

Bipolar derivatives having thermally activated delayed fluorescence (TADF) functions were synthesized by multistep synthetic procedure by using 3-(N,N-diphenylamino)-9H-carbazole and 9-(4-(4-fluorophenylsulfonyl)phenyl)carbazole or 4-(carbazol-9-yl)-4′-fluorobenzophenone in the final step. The materials have high thermal stabilities and form molecular glasses with very high glass transition temperatures of 140 °C–143 °C.The compounds were tested in multilayer TADF based organic light emitting diodes. The most efficient green device demonstrated low turn-on voltage of 2.2 V, maximum luminance of 60155 cd/m2 and high peak efficiency values of 12.1 % (35.4 cd/A and 46.3 lm/W). The device maintained high efficiency at practical luminance levels of 100 cd/m2 and 1000 cd/m2, registering 12.1 % and 11.1 %, respectively.

B-N/B-O Contained Heterocycles as Fusion Locker in Multi-Resonance Frameworks towards Highly-efficient and Stable Ultra-Narrowband Emission.

Fusing condensed aromatics into multi-resonance (MR) frameworks has been an exquisite strategy to modulate the optoelectronic properties, which, however, always sacrifices the small full width at half maxima (FWHM). Herein, we strategically embed B-N/B-O contained heterocycles as fusion locker into classical MR prototypes, which could enlarge the π-extension and alleviate the steric repulsion for an enhanced planar skeleton to suppress the high-frequency stretching/ scissoring vibrations for ultra-narrowband emissions. Sky-blue emitters with extremely small FWHMs of 17-18 nm are thereafter obtained for the targeted emitters, decreased by (1.4-1.9)-fold compared with the prototypes. Benefiting from their high photoluminescence quantum yields of >90 % and fast radiative decay rates of >108 s-1 , one of those emitters shows a high maximum external quantum efficiency of 31.9 % in sensitized devices, which remains 25.8 % at a practical luminance of 1,000 cd m-2 with a small FWHM of merely 19 nm. Notably a long operation half-lifetime of 1,278 h is also recorded for the same device, representing one of the longest lifetimes among sky-blue devices based on MR emitters.

B−N/B−O Contained Heterocycles as Fusion Locker in Multi‐Resonance Frameworks towards Highly‐efficient and Stable Ultra‐Narrowband Emission

AbstractFusing condensed aromatics into multi‐resonance (MR) frameworks has been an exquisite strategy to modulate the optoelectronic properties, which, however, always sacrifices the small full width at half maxima (FWHM). Herein, we strategically embed B−N/B−O contained heterocycles as fusion locker into classical MR prototypes, which could enlarge the π‐extension and alleviate the steric repulsion for an enhanced planar skeleton to suppress the high‐frequency stretching/ scissoring vibrations for ultra‐narrowband emissions. Sky‐blue emitters with extremely small FWHMs of 17–18 nm are thereafter obtained for the targeted emitters, decreased by (1.4–1.9)‐fold compared with the prototypes. Benefiting from their high photoluminescence quantum yields of >90 % and fast radiative decay rates of >108 s−1, one of those emitters shows a high maximum external quantum efficiency of 31.9 % in sensitized devices, which remains 25.8 % at a practical luminance of 1,000 cd m−2 with a small FWHM of merely 19 nm. Notably a long operation half‐lifetime of 1,278 h is also recorded for the same device, representing one of the longest lifetimes among sky‐blue devices based on MR emitters.

Overcoming power efficiency limitation of white fluorescence light‐emitting diodes via multilevel‐hydrogen‐bond matrix

AbstractHigh power efficiency and low efficiency roll‐off at practical luminance are two requirements for new‐generation energy‐saving lighting technologies, which are still bottlenecks of thermally activated delayed fluorescence (TADF) white organic light‐emitting diodes (WOLED), despite the advantages of TADF materials and devices in low cost and high sustainability. Herein, we developed a spiro phosphine oxide host named SSOXSPO, which can form multiple and multidirectional intermolecular hydrogen bonds (IHB). The resulted multilevel IHB network integrates long‐range ordered and short‐range disordered alignments for suppressing triplet‐polaron quenching (TPQ) and triplet‐triplet annihilation (TTA). Electronic characteristics of SSOXSPO matrix are further regulated, leading to the optimal exciton allocation through balancing energy and charge transfer. As consequence, using SSOXSPO as host, the single‐emissive‐layer TADF WOLEDs realized the record performance, including ultralow operation voltage as ∼4.0 V, power efficiency beyond fluorescent tube (70.1 lm W−1) and negligible external quantum efficiency roll‐off (3%) at 1000 nits for indoor lighting. This work demonstrates that multiple interplays supported by host matrixes in TADF WOLEDs can facilitate the synergistic effects of TADF emitters on 100% exciton utilization.

Steric groups fusion strategy for green multi-resonance emitters toward efficient OLEDs with narrowband emission

Multi-resonance induced thermally activated delayed fluorescence (MR-TADF) emitters have demonstrated significant advantages in high-efficient organic light-emitting diodes (OLEDs) with wide color gamut due to their high photoluminescence quantum yields (ΦPL) and narrow spectra. Herein, two novel green MR-TADF emitters, MFCzBN and SFCzBN, were designed and synthesized by integrating steric groups into the classic framework of BNCz. These emitters exhibited narrowband green emission both in solution and films, fast radiative decay rates of approximately 108 s−1, as well as high ΦPL values of up to 90%. The fabricated vacuum-deposited OLEDs displayed bright green emission at 508 nm, achieving remarkable maximum external quantum efficiencies (EQEmax) of 24.3% and 24.7% for MFCzBN and SFCzBN, respectively. Notably, the MFCzBN-based device demonstrated low efficiency roll-off values of 1.6% and 2.5% at practical luminance of 100 cd m−2 and 1000 cd m−2. This work presents an effective strategy for attaining high-efficiency MR-OLEDs through the fusion of steric groups.

Phosphorescent ultrathin emitting layers sensitized by TADF interfacial exciplex enables simple and efficient monochrome/white organic light-emitting diodes

In this work, we proposed a novel scheme enabling simple and efficient monochrome/white organic light-emitting diodes (OLEDs) by simultaneously combining thermally activated delayed fluorescence (TADF) interfacial exciplex and phosphorescent ultrathin emitting layers (Ph-UEMLs). Specifically, monochrome/white OLEDs were structured by directly inserting single or complementary Ph-UEMLs into the interface of TADF interfacial exciplex (m-bis(N-carbazolyl)-benzene (mCP)/2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine (PO-T2T)) using simple doping-free technology. Consequently, all monochrome (blue, green, orange and red) OLEDs exhibit a low turn-on voltage of 2.4–2.5 V and realize ultra-high device performance with maximum external quantum efficiency (EQE) exceeding 20%. Therein, the Bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic)-based blue OLED achieves the forward-viewing EQE reaching 30.21%, which is among highest values ​reported in literatures. Moreover, the fabricated two-, three- and four-colors white OLEDs also obtain the same excellent performance with a low turn-on voltage of 2.5 V and high EQEs of 23.47, 22.70 and 23.88% (corresponding to 78.80, 76.70 and 70.89 lm/W). All white devices also exhibit extremely high color stability at a practical luminance range from about 5000 to 12000 cd/m2, indicating a huge potential application. It is demonstrated that Ph-UEMLs sensitized by TADF interfacial exciplex ensures a complete exciton utilization by multi-channels energy transfer from TADF interfacial exciplex to Ph-UEMLs, which is responsible for the main reason for achieving high device performance. We believe our proposed scheme paves a new path for developing ultra-simple and high-performance monochrome/white OLEDs.

Realization of Long Operational Lifetimes in Vacuum-Deposited Organic Light-Emitting Devices Based on para-Substituted Pyridine Carbazolylgold(III) C^C^N Complexes.

A new series of robust C^C^N carbazolylgold(III) complexes is designed and synthesized through the introduction of inert and sterically bulky oligophenyl substituents on the pyridyl moiety of the cyclometalating ligand. High photoluminescence quantum yields of up to 96% are recorded with these complexes doped in solid-state thin films, and short excited-state lifetimes of 0.3 μs or less in the solid state at room temperature are found. Promising electroluminescence (EL) performances are shown by the vacuum-deposited organic light-emitting devices (OLEDs) based on this series of gold(III) complexes. High external quantum efficiencies of up to 19.5% with efficiency roll-offs of down to 10% at a practical luminance brightness level of 1000 cd m-2 are achieved. More importantly, record-long operational lifetimes (LT50) of up to 470,700 h at 100 cd m-2 are realized, which is currently the highest value among all classes of gold(III) complexes with tridentate pincer ligands. Particularly, by introducing a sterically bulky terphenyl moiety on the reactive site of the pyridine ring, the LT50 value is shown to attain ∼7 times longer half-lifetime than that based on the unsubstituted complex. These unprecedented EL performances and the simple synthetic route in a mercury-free fashion make them promising emitting materials for practical OLEDs toward commercialization.

Achieving Efficient Solution‐Processed Blue Narrowband Emitting OLEDs with Small Efficiency Roll‐Off by Using a Bulky TADF Sensitizer with High Reverse Intersystem Crossing Rate

AbstractSolution‐processed organic light‐emitting diodes (OLEDs) based on multiple‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters exhibit high color purity for next‐generation ultrahigh‐definition display. However, they suffer from low efficiency and large efficiency roll‐off due to slow triplet exciton upconversion of MR‐TADF emitters, resulting in serious triplet exciton quenching. Here, efficient solution‐processed blue MR‐TADF OLEDs featured with small efficiency roll‐off are developed by using a new bulky TADF sensitizer consisting of five di‐tert‐butylcarbazoles and one triazine with high reverse intersystem crossing rate of 2.0 × 107 s−1, which can rapidly convert triplet excitons to singlet ones to avoid exciton quenching. The Dexter energy transfer from the sensitizer to the MR‐TADF emitter is blocked by using tertiary butyl groups as the bulky unit in the sensitizer to increase the intermolecular distance for ensuring fast upconversion of triplet excitons on the sensitizer. And then the singlet excitons on sensitizer transfer to the emitter through long‐range Förster resonance energy transfer for narrowband emission. As a result, a maximum external quantum efficiency of 23.9% is achieved for the sensitized devices, slightly declining to 21.5% at a practical luminance of 1000 cd m−2. To the best of the authors’ knowledge, this is the best result for solution‐processed blue MR‐TADF OLEDs.

Carbazole and triazine-based bipolar hosts with extremely low efficiency roll-offs for green PhOLEDs

In this paper, two new bipolar host materials (CZ-p-TRZ and CZ-m-TRZ) which consist of 9-phenylcarbazole as the donor and 2,4,6-triphenyl-1,3,5-triazine as the acceptor were synthesized and characterized. Two compounds exhibit excellent thermal stability and appropriate triplet energy levels (ET). Based on the above advantages, Ir(ppy)3-based green phosphorescent organic light-emitting diodes (PhOLEDs) were fabricated with CZ-p-TRZ and CZ-m-TRZ as host. Both PhOLEDs show good performance with maximum external quantum efficiencies (EQEmax) of 16.83 and 19.40%, respectively. Especially, two devices also exhibit extremely small efficiency roll-off, and at a practical luminance of 1000 cd/m2, only 0.1% drop in efficiency was observed for two devices, which is among the best results ever reported as green bipolar hosts.

A simple bipolar host material based on triphenylamine and pyridine featuring σ-linkage for efficient solution-processed phosphorescent organic light-emitting diodes

Solution-processable host materials play an important role in achieving highly efficient and cost-effective phosphorescent organic light-emitting diodes (PhOLEDs). This paper designed and prepared a simple solution-processable host material of TPA-PyF2 based on triphenylamine and pyridine to fabricate efficient solution-processed PhOLEDs. TPA-PyF2 featured an σ-linkage between the electron donor and acceptor units, which not only served to limit the conjugation length of the molecule and maintain a high triplet energy level, but also endowed the host molecule with a three-dimensional structure to enable high film morphological stability for solution processing. As a result, TPA-PyF2 exhibited a high triplet energy level (2.82 eV), high thermal stability, bipolar charge transfer, and excellent film morphology. Blue solution-processed OLED with a simple double-layer structure based on TPA-PyF2 host achieved a maximum current efficiency, power efficiency, and luminance of 17.2 cd/A, 7.1 lm/W, and 11519 cd/m2, respectively, with a small efficiency roll-off of only 9.1% at the practical luminance of 1000 cd/m2. This work reveals that the σ-linkage strategy is promising in designing efficient solution-processable host materials for high-efficiency PhOLEDs.

Novel Ortho‐Linkage Donor‐Acceptor Type Host Materials for Efficiently Red Phosphorescence Organic Light‐Emitting Diodes

AbstractHigh performance device is the key issue for organic light‐emitting diodes (OLEDs) industrialization. In this instance, efficient hosts, emitters, as well as other functional layer materials are essential for the realization of high‐performance OLEDs. Herein, we develop a series of D−A type host materials, TPATRZ, CzTRZ, and POXTRZ with ortho‐linking strategy. The ortho‐linkage makes TPATRZ, CzTRZ, and POXTRZ highly twisted conformations, which reducing the degree of intramolecular conjugation and maintain high triplet energies of these materials. The red phosphorescence organic light emitting diodes by using Ir(piq)2(acac) as dopant, TPATRZ, CzTRZ, and POXTRZ as host materials achieved relative high device performance with over 20 % external quantum efficiency and flat efficiency roll‐off. The EQEs of the champion devices remain above 22 % at the practical luminance (500 and 1000 cd m−2). The device hosted by POXTRZ achieved the highest external quantum efficiency of 24.0 %, as well as smallest efficiency roll‐off of 6.3 % at 1000 cd m−2. These results further extend the possibilities of ortho‐linkage D−A type host materials and make them have a promising application in OLEDs.

Highly Robust CuI‐TADF Emitters for Vacuum‐Deposited OLEDs with Luminance up to 222 200 cd m−2 and Device Lifetimes (LT90) up to 1300 hours at an Initial Luminance of 1000 cd m−2

A critical step in advancing the practical application of copper-based organic light-emitting diodes (OLEDs) is to bridge the large gap between device efficiency and operational stability at practical luminance. Described is a panel of air- and thermally stable two-coordinate CuI emitters featuring bulky pyrazine- (PzIPr) or pyridine-fused N-heterocyclic carbene (PyIPr*) and carbazole (Cz) ligands with enhanced amide-Cu-carbene bonding interactions. These CuI emitters display thermally activated delayed fluorescence (TADF) from the 1 LL'CT(Cz→PzIPr/PyIPr*) excited states across the blue to red regions with exceptional radiative rate constants of 1.1-2.2×106 s-1 . Vapour-deposited OLEDs based on these CuI emitters showed excellent external quantum efficiencies and luminance up to 23.6 % and 222 200 cd m-2 , respectively, alongside record device lifetimes (LT90 ) up to 1300 h at 1000 cd m-2 under our laboratory conditions, highlighting the practicality of the CuI -TADF emitters.

Highly Robust CuI‐TADF Emitters for Vacuum‐Deposited OLEDs with Luminance up to 222 200 cd m−2 and Device Lifetimes (LT90) up to 1300 hours at an Initial Luminance of 1000 cd m−2

AbstractA critical step in advancing the practical application of copper‐based organic light‐emitting diodes (OLEDs) is to bridge the large gap between device efficiency and operational stability at practical luminance. Described is a panel of air‐ and thermally stable two‐coordinate CuI emitters featuring bulky pyrazine‐ (PzIPr) or pyridine‐fused N‐heterocyclic carbene (PyIPr*) and carbazole (Cz) ligands with enhanced amide‐Cu‐carbene bonding interactions. These CuI emitters display thermally activated delayed fluorescence (TADF) from the 1LL′CT(Cz→PzIPr/PyIPr*) excited states across the blue to red regions with exceptional radiative rate constants of 1.1–2.2×106 s−1. Vapour‐deposited OLEDs based on these CuI emitters showed excellent external quantum efficiencies and luminance up to 23.6 % and 222 200 cd m−2, respectively, alongside record device lifetimes (LT90) up to 1300 h at 1000 cd m−2 under our laboratory conditions, highlighting the practicality of the CuI‐TADF emitters.

Emission and Absorption Tuning in TADF B,N‐Doped Heptacenes: Toward Ideal‐Blue Hyperfluorescent OLEDs

AbstractDeveloping high‐efficiency purely organic blue organic light‐emitting diodes (OLEDs) that meet the stringent industry standards is a major current research challenge. Hyperfluorescent device approaches achieve in large measure the desired high performance by combining the advantages of a high‐efficiency thermally activated delayed fluorescence (TADF) assistant dopant with a narrowband deep‐blue multi‐resonant TADF (MR‐TADF) terminal emitter. However, this approach requires suitable spectral overlap to support Förster resonance energy transfer (FRET) between the two. Here, a color tuning of a recently reported MR‐TADF B,N‐heptacene core through control of the boron substituents is demonstrated. While there is little impact on the intrinsic TADF properties—as both singlet and triplet energies decrease in tandem—this approach improves the emission color coordinate as well as the spectral overlap for blue hyperfluorescence OLEDs (HF OLEDs). Crucially, the red‐shifted and more intense absorption allows the new MR‐TADF emitter to pair with a high‐performance TADF assistant dopant and achieve maximum external quantum efficiency (EQEmax) of 15% at color coordinates of (0.15 and 0.10). The efficiency values recorded for the device at a practical luminance of 100 cd m–2 are among the highest reported for HF TADF OLEDs with CIEy ≤ 0.1.