Electroluminescent Materials Research Articles

Electroluminescent Clusters.

Optoelectronic cluster materials emerge rapidly in recent years especially for light-emitting devices, owing to their 100 % exciton harvesting and unique organic-inorganic hybrid structures with tunable excited-state characteristics for thermally activated delayed fluorescence and/or phosphorescence and inheritable photo- and thermo-stability. However, for efficient electroluminescence, excited-state compositions of cluster emitters should be tuned through ligand engineering to enhance ligand-centered radiative components and reduce cluster-centered quenching states. Nonetheless, the balance of optoelectronic properties requires delicate and controllable ligand functionalization. On the other hand, in addition to balancing carrier fluxes, it showed that device engineering, especially host matrixes and interfacial optimization, can not only alleviate triplet quenching, but also modify processing and passivate defects. As consequence, the record external quantum efficiencies of cluster light-emitting diodes already reached ≈30 %. Herein, we overview recent progress of electroluminescent cluster materials and discuss their structure-property relationships, which would inspire the continuous efforts making cluster light-emitting diodes competent as the new generation of displays and lighting sources.

High‐Efficiency Ultraviolet Electroluminescence from Multi‐Resonance Phosphine Oxide Polycyclic Aromatics

AbstractEfficient ultraviolet (UV) electroluminescent materials remain a great challenge, since short peak wavelength <400 nm and narrow full width at half maximum (FWHM) <50 nm are simultaneously required. In this sense, multi‐resonance (MR) thermally activated delayed fluorescence (TADF) emitters featuring narrow‐band emissions hold the promise for UV applications. Herein, a novel MR‐TADF skeleton featuring carbazole‐phosphine oxide (P=O) fused aromatics is developed to construct the first two UV MR emitters named CzP2PO and tBCzP2PO. In addition to synergistic resonance effects of P=O and N atom, sp3‐hybrid P atom renders the curved polycyclic planes of CzP2PO and tBCzP2PO, giving rise to their narrowband UV emissions with peak wavelengths <390 nm and FWHM<35 nm. Besides configuration quasi‐planarization for radiation enhancement and quenching suppression, P=O moiety further enhances singlet‐triplet coupling to facilitate reverse intersystem crossing, resulting in the state‐of‐the‐art photoluminescence quantum yield of 62 % in tBCzP2PO doped films. As consequence, tBCzP2PO endowed its UV organic light‐emitting diodes with the peak at 382 nm and FWHM of 32 nm, and especially the record‐high external quantum efficiency (EQE) of 15.1 % among all kinds of UV devices. Our results demonstrate great potential of P=O based MR emitters in practical applications including optoelectronics, biology and medicine science.

High-Efficiency Ultraviolet Electroluminescence from Multi-Resonance Phosphine Oxide Polycyclic Aromatics.

Efficient ultraviolet (UV) electroluminescent materials remain a great challenge, since short peak wavelength <400 nm and narrow full width at half maximum (FWHM) <50 nm are simultaneously required. In this sense, multi-resonance (MR) thermally activated delayed fluorescence (TADF) emitters featuring narrow-band emissions hold the promise for UV applications. Herein, a novel MR-TADF skeleton featuring carbazole-phosphine oxide (P=O) fused aromatics is developed to construct the first two UV MR emitters named CzP2PO and tBCzP2PO. In addition to synergistic resonance effects of P=O and N atom, sp3 -hybrid P atom renders the curved polycyclic planes of CzP2PO and tBCzP2PO, giving rise to their narrowband UV emissions with peak wavelengths <390 nm and FWHM<35 nm. Besides configuration quasi-planarization for radiation enhancement and quenching suppression, P=O moiety further enhances singlet-triplet coupling to facilitate reverse intersystem crossing, resulting in the state-of-the-art photoluminescence quantum yield of 62 % in tBCzP2PO doped films. As consequence, tBCzP2PO endowed its UV organic light-emitting diodes with the peak at 382 nm and FWHM of 32 nm, and especially the record-high external quantum efficiency (EQE) of 15.1 % among all kinds of UV devices. Our results demonstrate great potential of P=O based MR emitters in practical applications including optoelectronics, biology and medicine science.

Highly efficient deep blue electroluminescent material with high and towards balanced carrier transmission performance based on hybrid local and charge-transfer (HLCT) excited state

Deep blue electroluminescent materials play a decisive role in organic light-emitting diodes (OLEDs). Herein, three novel deep blue molecules based on hybridized local and charge-transfer (HLCT) excited state were reported, namely CZFPY, CZFPI and TPAFPI. Single-crystal analysis of TPAFPI shows abundant intermolecular interactions, which restricts molecular rotation and suppresses structural vibrations, promotes TPAFPI achieved a high photoluminescence quantum yield (PLQY) up to 72 % in solid state. More importantly, these abundant intermolecular interactions significantly increase its carrier mobilities, with hole and electron mobilities as high as 1.2 × 10−5 cm2 V−1 s−1 and 5.4 × 10−6 cm2 V−1 s−1, respectively. Consequently, the non-doped OLED based on TPAFPI achieved excellent device performance, the maximum current efficiency (CEmax) is 12.4 cd/A, the maximum power efficiency (PEmax) is 14.0 lm W−1, the maximum external quantum efficiency (EQEmax) is 7.2 % with high device stability, the efficiency roll-off is only 4.7 % at 1000 cd m−2. What is more, the doped device of TPAFPI exhibits a higher EQEmax of 10.1 % with a higher color purity, the Commission International de L’Eclairage (CIE) coordinate is (0.15, 0.06), matching the National Television Standards Committee (NTSC) standard. The comprehensive performance of TPAFPI-based doped device is at the highest level in the field of deep blue OLEDs (0.06 ≤ CIEy ≤ 0.09).

Alternating Current Electroluminescence for Human-Interactive Sensing Displays.

The development of stimuli-interactive displays based on alternating current (AC)-driven electroluminescence (EL) is of great interest, owing to their simple device architectures suitable for wearable applications requiring resilient mechanical flexibility and stretchability. AC-EL displays can serve as emerging platforms for various human-interactive sensing displays (HISDs) where human information is electrically detected and directly visualized using EL, promoting the development of the interaction of human-machine technologies. This review provides a holistic overview of the latest developments in AC-EL displays with an emphasis on their applications for HISDs. AC-EL displays based on exciton recombination or impact excitations of hot electrons are classified into four representative groups depending upon their device architecture: 1) displays without insulating layers, 2) displays with single insulating layers, 3) displays with double insulating layers, and 4) displays with EL materials embedded in an insulating matrix. State-of-the-art AC HISDs are discussed. Furthermore, emerging stimuli-interactive AC-EL displays are described, followed by a discussion of scientific and engineering challenges and perspectives for future stimuli-interactive AC-EL displays serving as photo-electronic human-machine interfaces.

Effect of hole-transport layer thickness on the performance of organic light-emitting diodes

In this study, we investigated the influence of hole-transport layer thickness (0, 5, 10, 15, 20, 25, 30, 35 and 40 nm), N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine (α-NPD) on the performance of thermally evaporated multilayer organic light-emitting diodes (OLEDs) with tris(8-hydroxy-quinolinato)aluminium (Alq3) as electroluminescent material. A device with 5 nm α-NPD thickness showed a current density ∼30 times higher than without any α-NPD layer. However, the current density decreased as the α-NPD thickness increased beyond 5 nm. In contrast to the current density, the device efficiency improved as α-NPD layer thickness increased to 30 nm, after which a drop in efficiency was observed. The current efficiency of the device with 30 nm α-NPD thickness was 10 times higher than the device with 5 nm α-NPD thickness. The results indicated that hole-injection in OLEDs was more efficient with thin 5 nm α-NPD, while optimal efficiency was at 30 nm of α-NPD thickness.

Performance Improvement Based on Latitude Classification of Perovskite Light-Emitting Diodes

The Perovskite Light-emitting Diode (PeLED) can effectively convert light energy and electrical energy, and the study of Light-Emitting Diode (LED) is conducive to the efficient use of energy. Starting from the dimension classification of perovskite light-emitting diodes, this paper introduces the advantages of perovskite in different dimensions and the methods to improve the performance of perovskite light-emitting diodes. It is expected to realize the preparation of low-cost and high-performance perovskite light-emitting diodes. Light-emitting diodes or electroluminescent devices have many excellent properties such as high brightness, wide colour gamut, low power consumption, long life and environmental protection. They have been widely used in the field of display and lighting, and have become one of the most competitive products in the optoelectronic industry. With the development of the LED industry and the higher requirements for LED display in the new era, scientific researchers exploration of new electroluminescent materials has also been gradually strengthened. Among them, organic molecules and new low-dimensional halogenated perovskite have attracted much attention because of their many advantages. The performance of LED depends on the type of light-emitting material and device structure. It is also important to understand the light-emitting mechanism of such devices and their internal carrier transport mechanism. Studying the light-emitting mechanism and carrier transport mechanism of LEDs based on different light-emitting materials is not only of scientific significance, but also can provide a reliable theoretical basis for further improving their performance.

High and Balanced Bipolar‐Transporting Deep‐Blue HLCT Material for Efficient Monochrome and White OLEDs based on a Simple Phenanthroimidazole‐Dibenzothiophene Derivative

AbstractThe irreconcilable contradiction between wide bandgap and charge carriers injection/transport in deep‐blue organic electroluminescence materials is one of the largest bottlenecks restricting the development of organic light‐emitting diodes (OLEDs). Here, a multifunctional deep‐blue hybridized local and charge‐transfer material containing a phenanthroimidazole‐dibenzothiophene derivative that can act as an emitter as well as a host for phosphorescent OLEDs is reported. Owing to its high and balanced bipolar‐transporting ability, remarkable fluorescence efficiency, and suitable triplet energy level, the deep‐blue device with it as a neat emitter provides an external quantum efficiency (EQE) of 6.68%, while yellow and red phosphorescent OLEDs offer the EQEs of 25.35% and 22.19%, respectively. All of them exhibit low‐efficiency roll‐off characteristics. What's more amazing is that the fluorescent/phosphorescent hybrid white OLEDs achieve high power efficiencies and EQEs over 95.9 lm W−1 and 26.8%, and the values are still higher than 77.7 lm W−1 and 25.6% at the high luminance of 1000 cd m−2.

Room-temperature growth of perovskite single crystals via antisolvent-assisted confinement for high-performance electroluminescent devices

Organic-inorganic halide perovskite single crystals (OIHP-SCs) are promising light-emitting materials for bright electroluminescence (EL) devices due to their superior optoelectronic properties and excellent stability. However, the conventional high-temperature growth methods will inevitably disturb the ordered growth and introduce massive defects in OIHP-SCs, leading to the degradation of device performance. The preparation of thin OIHP-SCs with low trap-state densities for high-performance EL devices remains a formidable challenge. Here, we develop an efficient antisolvent-assisted confined growth (AACG) method for the room-temperature growth of formamidinium lead bromide (FAPbBr3) perovskite SCs. An antisolvent vapour environment is intentionally introduced in the spatially confined growth process to lower the free energy barrier for nucleation, enabling the growth of high-quality FAPbBr3 SCs at room temperature. Consequently, FAPbBr3 SCs with ultralow trap-state density of 2.15 × 109 cm−3 and amplified spontaneous emission (ASE) threshold of 7.1 µJ cm−2 could be achieved, representing the best results ever reported for FAPbBr3 SCs. By leveraging the high crystal quality of FAPbBr3 SCs, SC-based perovskite light-emitting diodes (PeLEDs) with a high luminance of over 26,000 cd m−2 and a peak current efficiency (CE) of 13.02 cd A−1 are demonstrated. Our work opens up new opportunities for the development of high-performance EL devices based on OIHP-SCs.

Frontier Molecular Orbital Engineering: Constructing Highly Efficient Narrowband Organic Electroluminescent Materials.

It is of great strategic significance to develop highly efficient narrowband organic electroluminescent materials that can be utilized to manufacture ultra-high-definition (UHD) displays and meet or approach the requirements of Broadcast Television 2020 (B.T.2020) color gamut standards. This motif poses challenges for molecular design and synthesis, especially for developing generality, diversity, scalability, and robustness of molecular structures. The emergence of multiple resonance thermally activated delayed fluorescence (MR-TADF) emitters has ingeniously solved the problems and demonstrated bright application prospects in the field of UHD displays, sparking a research boom. This Minireview summarizes the research endeavors of narrowband organic electroluminescent materials, with emphasis on the tremendous contribution of frontier molecular orbital engineering (FMOE) strategy. It combines the outstanding advantages of MR framework and donor-acceptor (D-A) structure, and can achieve red-shift and narrowband emission simultaneously, which is of great significance in the development of long-wavelength narrowband emitters with emission maxima especially exceeding 500 nm. We hope that this Minireview would provide some inspiration for what could transpire in the future.

Frontier Molecular Orbital Engineering: Constructing Highly Efficient Narrowband Organic Electroluminescent Materials

AbstractIt is of great strategic significance to develop highly efficient narrowband organic electroluminescent materials that can be utilized to manufacture ultra‐high‐definition (UHD) displays and meet or approach the requirements of Broadcast Television 2020 (B.T.2020) color gamut standards. This motif poses challenges for molecular design and synthesis, especially for developing generality, diversity, scalability, and robustness of molecular structures. The emergence of multiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters has ingeniously solved the problems and demonstrated bright application prospects in the field of UHD displays, sparking a research boom. This Minireview summarizes the research endeavors of narrowband organic electroluminescent materials, with emphasis on the tremendous contribution of frontier molecular orbital engineering (FMOE) strategy. It combines the outstanding advantages of MR framework and donor‐acceptor (D−A) structure, and can achieve red‐shift and narrowband emission simultaneously, which is of great significance in the development of long‐wavelength narrowband emitters with emission maxima especially exceeding 500 nm. We hope that this Minireview would provide some inspiration for what could transpire in the future.

(Invited) Structural and Dynamics Analysis of Organic Semiconducting Materials by Solid State NMR

Recently, our group have successfully developed several blue and green thermally activated delayed fluorescence (TADF) emitters showing high external quantum efficiencies in OLEDs through high-throughput screening based on quantum chemical calculations. Although the conformation, aggregated structure and dynamics of TADF emitters in amorphous states is expected to be the origin of reverse intersystem crossing and resulting high device performance, the experimental approach toward these information is still limited because typical diffraction technique cannot be used to amorphous materials due to the lack of long-range order. Thus we have carried out multiscale simulations and solid-state NMR (ssNMR) analysis of organic amorphous thin films. The ssNMR is one of the powerful technique to obtain the structural and dynamics information of amorphous aggregated materials. In this presentation, we demonstrate structural and dynamics analysis of amorphous organic semiconducting materials using ssNMR.Reference(1) “Analysis of Molecular Orientation in Organic Semiconducting Thin Films Using Static Dynamic Nuclear Polarization Enhanced Solid-State NMR Spectroscopy”, Suzuki, K.; Kubo, S.; Aussenac, F.; Engelke, F.; Fukushima, T.; Kaji, H. Angew. Chem. Int. Ed. 2017, 56, 14842.(2) “Efficient blue thermally activated delayed fluorescence emitters showing very fast reverse intersystem crossing”, Ren, Y., Wada, Y., Suzuki, K., Kusakabe, Y., Geldsetzer, J. and Kaji, H. Appl. Phys. Express, 2021, 14, 071003.(3) “Solution-processable thermally activated delayed fluorescence emitters for application in organic light emitting diodes”, Suzuki, K.; Adachi, C.; Kaji, H. J. Soc. Inf. Disp. 2017, 25, 480.(4) “Imidazole Acceptor for Both Vacuum-Processable and Solution-Processable Efficient Blue Thermally Activated Delayed Fluorescence”, Kusakabe, Y.; Wada, Y.; Misono, T.; Suzuki, K.; Shizu, K.; Kaji, H ACS Omega, 7, 16740 - 16745 (2022).(5) “Triarylboron-based Fluorescent Organic Light-emitting Diodes with External Quantum Efficiencies Exceeding 20%”, Suzuki, K.; Kubo, S.; Shizu, K.; Fukushima, T.; Wakamiya, A.; Murata, Y.; Adachi, C.; Kaji, H.; Angew. Chem. Int. Ed. 2015, 54, 15231.(5) “Purely organic electroluminescent material realizing 100% conversion from electricity to light”, Kaji, H.; Suzuki, H.; Fukushima, T.; Shizu, K.; Suzuki, K.; Kubo, S.; Komino, T.; Oiwa, H.; Suzuki, F.; Wakamiya, A.; Murata, Y.; Adachi, C. Nat. Commun. 2015, 6, 8476.

Facile and scalable fabrication process of electroluminescent filament with high luminescent efficiency

Electroluminescent (EL) filament has received much more attention on the application of smart and displayable textiles. In this work, the co-axial wet-spinning method was utilized to prepare a core/sheath filament with a copper wire as core electrode and thermal polyurethane (TPU) contained EL material of ZnS:Cu as sheath. The outside was wire-winded helically and then was coated with silver coating via magnetron sputtering, which was used as the other electrode. About 10 nm thickness silver coating was afforded after 90 s sputtering, which ensured Ag coating continuity. Finally, the filament was immersed into a waterborne polyurethane (WPU) emulsion to endow a transparent protective layer. When the ratio of Zn:S/TPU was 1:1, the as-obtained EL filament exhibited the highest luminescent efficiency. This strategy made almost all EL materials excited, which provided a promising and facilely scalable method to fabricate EL filament with high utilization rate of EL materials and luminescent efficiency.

P‐173: Late‐News Poster: Composite Cavity Design for Long Lifetime and Low Cost Organic Light‐Emitting Diodes Displays

Traditional way to upgrade the stability and current efficiency performance of OLED device is seeking for new generation of electroluminescent materials. We provide a composite cavity design for longer lifetime, lower cost, and equivalent luminance by using the same materials. It consists of two first‐order red and green cavities and a second‐order blue cavity, which means different optical thickness of the RGB micro cavities. Due to the shorter distance between emitting molecules and metal electrodes, 1st order cavity obtains longer lifetime by surface plasmon coupling. A 52.7% improvement of calculated white lifetime can be accomplished with a respective 89.1% and 54.9% longer lifetime of red and green devices. 1/3 even more organic materials can be saved. Less angular luminance decay and lower working voltage are also demonstrated in the experimental part.

Multi‐Resonance Building‐Block‐Based Electroluminescent Material: Lengthening Emission Maximum and Shortening Delayed Fluorescence Lifetime

AbstractMulti‐resonance thermally activated delayed fluorescence (MR‐TADF) materials are considered a class of organic materials with exceptional electronic and optical properties, which make them promising for the applications in organic light‐emitting diodes (OLEDs). In this study, we improved, synthesized, and characterized a multiple‐resonance type emitter based on the assembly of MR‐building blocks (MR‐BBs). By optimizing the geometric arrangement of MR‐BBs, we were able to generate narrowband emission in the longer wavelength region and shorten the delayed excited‐state lifetime, resulting in improved emission efficiency compared to the parent molecule. Our proof‐of‐concept molecule, m‐DBCz, exhibited narrowband yellowish‐green TADF emission with a full width at half‐maximum of 32 nm and a small singlet‐triplet energy gap of 0.04 eV. The OLED developed using m‐DBCz as the emitter demonstrated electroluminescence at 548 nm and achieved a high external quantum efficiency (EQE) of 34.9 %. Further optimization of the device resulted in a high external quantum efficiency of 36.3 % and extremely low efficiency roll‐off, with EQE values of 30.1 % and 27.7 % obtained even at high luminance levels of 50 000 and 100 000 cd m−2. These results demonstrate the full potential of MR‐TADF materials for applications on ultrahigh‐luminance OLEDs.

Multi-Resonance Building-Block-Based Electroluminescent Material: Lengthening Emission Maximum and Shortening Delayed Fluorescence Lifetime.

Multi-resonance thermally activated delayed fluorescence (MR-TADF) materials are considered a class of organic materials with exceptional electronic and optical properties, which make them promising for the applications in organic light-emitting diodes (OLEDs). In this study, we improved, synthesized, and characterized a multiple-resonance type emitter based on the assembly of MR-building blocks (MR-BBs). By optimizing the geometric arrangement of MR-BBs, we were able to generate narrowband emission in the longer wavelength region and shorten the delayed excited-state lifetime, resulting in improved emission efficiency compared to the parent molecule. Our proof-of-concept molecule, m-DBCz, exhibited narrowband yellowish-green TADF emission with a full width at half-maximum of 32 nm and a small singlet-triplet energy gap of 0.04 eV. The OLED developed using m-DBCz as the emitter demonstrated electroluminescence at 548 nm and achieved a high external quantum efficiency (EQE) of 34.9 %. Further optimization of the device resulted in a high external quantum efficiency of 36.3 % and extremely low efficiency roll-off, with EQE values of 30.1 % and 27.7 % obtained even at high luminance levels of 50 000 and 100 000 cd m-2 . These results demonstrate the full potential of MR-TADF materials for applications on ultrahigh-luminance OLEDs.

Continuous-Flow Suzuki-Miyaura Coupling in Water and Organic Solvents Promoted by Blends of Stabilized Convoluted Polymeric Palladium Catalysts and Polymeric Auxiliary Materials.

Given that heterogeneous palladium-catalyzed C-C bond formation reactions under continuous-flow conditions are well suited for the efficient and safe production of pharmaceuticals and functional materials, the development of active and durable catalysts for this purpose is a matter of high practical significance. Here, a previously established molecular convolution methodology was used to synthesize catalysts for Suzuki-Miyaura coupling under flow conditions by blending convoluted polymeric palladium catalysts (prepared from copolymers of 4-vinylpyridine and 4-tert-butylstyrene) and crosslinked polymeric auxiliary materials (prepared from copolymers of divinylbenzene and 4-tert-butylstyrene). The optimal catalyst exhibited high performance and durability and allowed numerous biaryl products such as liquid-crystalline materials, organic electroluminescent materials, and pharmaceuticals to be continuously synthesized with turnover frequencies of up to 238 h-1 . In a demonstration of practical utility, the developed catalytic system was used for the continuous synthesis of two pharmaceuticals (felbinac and fenbufen) in water as the sole solvent.

Single‐Crystal Perovskite Light‐Emitting Diodes with External Quantum Efficiency of over 8% Enabled by Nonstoichiometric Composition Tuning

AbstractPerovskite single crystals (SCs) have been emerging as promising materials for electroluminescence (EL) device applications owing to their superior optoelectronic properties. However, the device performance of single‐crystal perovskite light‐emitting diodes (SC‐PeLEDs) is limited by the lack of effective defect management and energy level modulation. Here, a nonstoichiometric composition tuning (NCT) strategy for the construction of high‐performance SC‐PeLEDs is reported. The NCT strategy, finely tuning the MABr (MA+ = CH3NH3+) excess in the nonstoichiometric MAPbBr3 SCs to enhance the crystal quality, reduce the trap density, and elevate the energy level of the resultant perovskite SC, enables markedly decreased nonradiative recombination and more efficient carrier injection for the devices. In consequence, the optimized SC‐PeLEDs exhibit an ultrahigh peak luminance of 161 900 cd m−2 and a large external quantum efficiency (EQE) of up to 8.1%, representing the most efficient SC‐PeLED reported thus far. This strategy also shows a high universality in enhancing the EL performance of other lead bromide perovskite SC‐PeLEDs, endowing them with luminances and EQEs three times larger than those of the pristine devices. This work opens an avenue for the development of high‐performance EL devices based on perovskite SCs.

True- to Sky-Blue Emitters Bearing the Thiazolo[5,4-d]thiazole Electron Acceptor for Single and Tandem Organic Light-Emitting Diodes

A series of emitters displaying efficient photoluminescence (PL) and electroluminescence (EL) into the true- to sky-blue regions is herein described and employed as electroluminescent materials for the fabrication of efficient blue organic light-emitting diodes (OLEDs). The compounds possess linear, yet a twisted, donor−π–acceptor−π–donor (D−π–A−π–D) architecture, where D and A are a (substituted) carbazole (Cz) and thiazolo[5,4-d]thiazole (TzTz) moiety as the electron donor and accepting unit, respectively. D = 9H-carbazol-9-yl and 3,6-di-tert-butyl-9H-carbazol-9-yl for compounds TzTz-PCz2 and TzTz-PtbCz2, respectively. In dilute CH2Cl2 solutions, both compounds display intense (PL quantum yield = 60–74%) and short-lived (τ = ca. 0.8–2.0 ns) luminescence arising from an intramolecular charge-transfer (1ICT) excited state and falling into the sky-blue to the greenish-blue region (λem = 448–502 nm). Compared to the previously reported TzTz-TPA parental emitters that features two triphenylamine (TPA) donor groups, the highly twisted nature and less extended π-conjugation of the donor–acceptor TzTz-PCz2 and TzTz-PtbCz2 counterparts herein presented enable to widen the HOMO–LUMO energy gaps and warrant blue shifting of the emission. Finally, OLED devices fabricated by employing the herein proposed emitters are presented as well with both single- and tandem-device architectures. The so-prepared OLEDs display true-blue to sky-blue EL peaking at λEL,max = 460 nm (TzTz-PCz2) and 467–470 nm (TzTz-PtbCz2) and achieve maximum external quantum efficiency and luminance of 10.2% and 44,851 cd m–2 (for TzTz-PtbCz2) in the case of a tandem device, respectively, with a mitigated roll-off efficiency. These results demonstrate that the tandem device employing these TzTz donor–acceptor blue emitters raises the feasibility of fluorescent compounds to compete with other potential emitters in practical applications.

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