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Novel host materials and their molecular design methods for phosphorescent materials are crucial for the application of phosphorescent organic light emitting diodes (PhOLEDs), which require balanced carrier injection and sufficient triplet energy levels (ET). Herein, two host materials, namely PPI22PPPBO and PPI33PPPBO, are designed by varying the linkage of benzoxazole (PBO) and phenanthroimidazole (PPI) groups with appropriate ET for green, yellow, and red phosphors. The meta‐link PPI33PPPBO is not only of smaller π‐conjugation, but also of more ordered face‐to‐face stacking for enhanced and more balanced carrier mobility. As a result, the green, yellow, and red PhOLEDs utilizing PPI33PPPBO as host materials show low turn‐on voltages of 2.8 V. The maximum external quantum efficiency (EQEmax) of the corresponding devices reaches 22.8%, 26.7%, and 17.6%, which is superior to that of the traditional host materials CBP and mCP, showing great application potential. More importantly, when the luminance is 1000 cd m−2, their EQE can still be as high as 21.9%, 25.5%, and 16.4%, corresponding to negligible efficiency roll‐offs of only 3.9%, 4.5%, and 6.8%. To the best of authors knowledge, it is the first time that PBO is applied to PhOLED host materials using a twisted connection method. [ABSTRACT FROM AUTHOR]

High efficiency and luminance are critical for commercialized blue organic light‐emitting diodes (OLEDs). Herein, a novel donor–acceptor (D–A) blue‐emissive molecule with a weak donor and acceptor is synthesized. The moderate hybrid local and charge transfer (HLCT) state character endows PPIBPO with blue fluorescence and high quantum efficiency. More importantly, the rigid, rod‐like molecular structure gives rise to the regularity of the stacking pattern of PPIBPO, which enables its extraordinary carrier mobilities in non‐doped OLED, the hole mobility and electron mobility are as high as 5.09 × 10−5 cm2 V−1 s−1 and 3.22 × 10−4 cm2 V−1 s−1, respectively. The non‐doped blue OLED of PPIBPO achieves a maximum external quantum efficiency (EQE) of 12.0% and a maximum luminance of 55023 cd m−2, which is one of the best values among the non‐doped blue OLEDs based on HLCT molecules. Furthermore, high‐efficiency two‐color hybrid warm white OLED with a maximum EQE up to 22.5% and maximum power efficiency of 87.0 lm W−1 is also achieved using PPIBPO as blue‐fluorophor. [ABSTRACT FROM AUTHOR]

One of the most important issues of the organic light‐emitting diode (OLED) is the highly efficient blue‐emissive material, which demands both excellent photoluminescent quantum yield (PLQY) and balanced carrier mobilities. Herein, a series of blue‐emissive donor–π–acceptor (D–π–A) materials with fluorene π‐bridge and their D–A analogues are synthesized and discovered with a theoretical combined experimental method. Based on the excellent electron mobility of the oxadiazole (OXZ) acceptor, it is further proven that the insertion of the fluorene π‐bridge can not only contribute to the formation of hybrid local and charge‐transfer excited state with high PLQY, but also give rise to the hole mobilities by enhanced intermolecular face‐to‐face stacking. As a result, the non‐doped OLED of TPACFOXZ exhibits a high maximum external quantum efficiency approaching 10% with boosted and balanced hole and electron mobilities of 5.60 × 10−5 and 6.60 × 10−5 cm2 V−1 s−1, respectively, which are among the best results of the non‐doped blue fluorescent OLEDs. [ABSTRACT FROM AUTHOR]

Due to the energy gap law, red emission needs relatively narrow energy gap, thus the nonradiative transition rate (k nr) grows exponentially and eventually impacts the materials fluorescent efficiency. Here, an orange-red emission donor-acceptor-π-donor (D-A-π-D') material N , N -diphenyl-4-(7-(4-(10-phenyl-10 H -phenoxazin-3-yl) phenyl) benzo [c] (Huang et al., 2019; Park et al., 2008; Caspar et al., 1982) [1,2,5] thiadiazol-4-yl) aniline (TBphPP) was designed and synthesized. Introducing a benzene π-bridge between the strong donor 10-phenyl-10 H -phenoxazin (PPOX) and acceptor 2,1,3-benzothiadiazole (BTZ) not only is able to stretch the molecular conjugation so as to increase the proportion of LE state in hybrid local and charge-transfer (HLCT) state but also increase the overlap area of the electron cloud to improve luminous efficiency. As a result, the non-doped organic light-emitting diode (OLED) of TBphPP exhibited high luminance of 17,886 cd m−2 and relatively high exciton utilization efficiency (EUE) of 44 % with a standard red electroluminescent peak at 620 nm. Importantly, the optimized doped device based on TBphPP achieved high performance that the maximum external quantum efficiency (EQE max) was up to 9.86 % with a higher EUE of 66.2 % and the efficiency roll-off (η roll-off) at 100,000 cd m−2 was only 3.55 %. Simultaneously, it has reached ultra-high luminescence of 180,583 cd m−2, high current efficiency of 29.02 cd A−1 and power efficiency of 16.47 l m W−1. To our knowledge, the TBphPP device with such ultra-high luminance and high efficiency is one of the best performance orange-red materials based on HLCT characteristic. This work achieves high efficiency, low efficiency roll-off and ultra-high luminance in red OLEDs with HLCT characteristic, which is based on the molecule design that introducing a benzene π-bridge between the strong donor PPOX and acceptor BTZ not only is able to stretch the molecular conjugation so as to increase the proportion of LE state in HLCT state but also increase the overlap area of the electron cloud to improve luminous efficiency. [Display omitted] • A novel red material with HLCT excited state was designed and synthesized. • High-performance doped OLED with ultra-high luminance up to 180,583 cd m−2 • Optimistic doped OLED with EQE of 9.86 % and η roll-off at 100,000 cd m−2 of 3.55 %. • One of the best orange-red HLCT devices with ultra-high luminance and high EQE. [ABSTRACT FROM AUTHOR]

Organic light-emitting diodes (OLEDs) and room temperature phosphorescence (RTP) materials have attracted great interests for their wide application in lighting and other fields. How to efficiently utilize triplet excitons to achieve the multifunctionality of OLED and RTP simultaneously is a major challenge. Herein, two blue molecules, 3PCZFB and 3PCZBF were reported. Theoretical calculations indicate that both molecules possess hybrid localized charge transfer (HLCT) characteristic. More importantly, both can simultaneously obtain electro-fluorescence and RTP properties by multiple harvesting of triplet excitons with high spin-orbit coupling matrix element (SOCME). The introduction of benzoyl fluorene increased the contribution of the n-orbital, resulting in a high SOCME, which is beneficial to both high exciton utilization efficiency (EUE) and RTP. The non-doped OLED of 3PCZFB achieved maximum external quantum efficiency (EQE max) of 4.9 % and EUE of 58.6 % at 459 nm. Besides, 0.1 % 3PCZFB and 3PCZBF doped in PMMA sheets achieve RTP efficiencies of 6.6 % at 524 nm and 25.9 % at 506 nm, as well as lifetimes of 379.8 ms and 204.8 ms. This is the first time Benzoyl fluorene-based molecules achieved dual-function applications in OLED and RTP by utilizing and recycling triplet excitons of T 1. [Display omitted] • Two new benzoyl fluorene-based blue emitters namely 3PCZFB and 3PCZBF are designed and synthesized. • Benzoyl fluorene-based molecules achieved dual functional application in OLED and RTP for the first time. • Non-doped blue OLED based on 3PCZFB molecule exhibits the efficiency roll-off is only 6.1 % at 1000 cd m−2. • 0.1 % 3PCZFB molecule doped PMMA sheets obtain the RTP lifetime of 379.8 ms. [ABSTRACT FROM AUTHOR]

• Construction of three electroluminescent materials with HLCT excited state. • Near-infrared OLED with high exciton utilization efficiency. • High-performance HLCT-based OLED with EQE of 9.55 %@662 nm and CIE of (0.66, 0.34). • One of the highest performances achieved in deep red HLCT-based OLEDs. Although the hot exciton mechanism with hybridized local and charge-transfer (HLCT) characteristics is a promising molecular design strategy, there are few organic deep red (DR) and near-infrared (NIR) HLCT-type emitters with high external quantum efficiency (EQE). Herein, this work reports three DR/NIR emitters with high EQE, TNZ-3PPOXP, TPANZPOXP, and 2PPOXNZ. These emitters show DR/NIR emission in the neat film, 664 nm for TNZ-3PPOXP, 718 nm for TPANZPOXP, and 724 nm for 2PPOXNZ. Interestingly, the emitters all possess hybridized local and charge-transfer (HLCT) characteristics and potential hot exciton channels. The corresponding non-doped OLED achieve high exciton utilization efficiency (EUE) and NIR emission, 55.6 %@694 nm for TNZ-3PPOXP, 82.8 %@736 nm for TPANZPOXP, and 42.3 %@756 nm for 2PPOXNZ. More importantly, with these emitters as the guest, PO-01 as the phosphorescent sensitizer, and CBP as the host, the sensitization device achieved nearly 10 % EQE, 9.55 %@662 nm for TNZ-3PPOXP, 4.20 %@699 nm for TPANZPOXP, and 4.49 %@702 nm for 2PPOXNZ. To our knowledge, this is one of the highest device efficiencies based on HLCT as the guest. [ABSTRACT FROM AUTHOR]

Abstract Controlling the conjugate degree of the molecules and regulating the properties of excited states are critical for determining the photoluminescence (PL) and electroluminescence (EL) properties of twisted donor–acceptor (D–A) type blue emitters. Here, two novel phenothiazine-based blue emitters derivatives, 10-ethyl-3-(4-(1-phenyl-1H-phenanthro [9,10-d]imidazol-2-yl)phenyl)-10H-phenothiazine (PHPPI) and 10-ethyl-3-(3-(1-phenyl-1H-phenanthro [9,10-d]imidazol-2-yl)phenyl)-10H-phenothiazine (MPHPPI), are successfully synthesized and their thermal, photophysics, theoretical calculations and electronic properties are fully investigated. By merging two simple donor and acceptor units together through different linking positions of the bridging benzene ring (para- and meta-position), the π-conjugation length is effectively controlled to ensure the deep-blue emission. The non-doped devices using the PHPPI and the MPHPPI emitters exhibit EQE max (external quantum efficiency) of 4.14% and 2.23% with maximum luminous efficiency (LE max) of 11.06 cd A−1 and 3.52 cd A−1, and EL emission peak of 496 nm and 464 nm, respectively. Whereas, the doped MPHPPI-based device exhibits color-pure deep blue EL performance with an emission peak at 460 nm, corresponding to the Commission Internationale de L'Eclairage coordinates of (0.15, 0.17), and a maximum EQE of 3.96%. To the best of our knowledge, this is the most efficient and color-pure deep blue OLED based on phenothiazine as a donor material reported thus far. The results of this study not only provide a better understanding of the relationship between the structure of the D-A system and the EL properties, but also provide a novel and versatile method for the design of deep blue emitters based on phenothiazine as a donor material. Graphical abstract Image 1 Highlights • Two novel blue-emitting molecules, PHPPI and MPHPPI, with different coupling positions were synthesized. • The MPHPPI-doped device emitted 460-nm bright deep blue emission with CIE coordinates of (0.15, 0.17). • This is the most efficient and color-purity deep blue OLED based on phenothiazine as the donor material reported thus far. [ABSTRACT FROM AUTHOR]

Due to the limitation of the energy gap rule, the development of highly efficient deep red hot-exciton material (λ EL ≥ 650 nm) remains a great challenge. Here, we designed and synthesized a novel D-A-D type deep red fluorescent molecule, 4,7-bis(10-phenyl-10 H -phenoxazin-3-yl)benzo[c][1,2,5]thiadiazole (2PPOXBZ), which is not only efficient deep red emitter but also has high hole mobility (2.56 × 10−3 cm2 V−1 s−1). The excited-state characteristics were investigated through photophysical experiments and theoretical calculations, it had been demonstrated the hot-exciton properties. The optimized non-doped OLED using 2PPOXBZ simultaneously act as a light-emitting layer and the hole transport layer exhibits the maximum external quantum efficiency (EQE) as high as 3.38% with a deep red emission peak at 678 nm, corresponding to the Commission International de L'Eclairage (CIE) coordinates (0.70, 0.30). More importantly, the optimized doped deep red OLED based on 2PPOXBZ as dopant exhibits an EQE up to 7.52% with electroluminescence (EL) peak of 658 nm and CIE coordinates of (0.67, 0.33), which is among the best results based on "Hot-exciton" deep red fluorescent OLEDs at present. The results of this study not only realize highly efficient deep red OLEDs with high color purity but also provide an effective molecular strategy for efficient deep red EL emitters. [Display omitted] • Novel D-A-D type deep red hot-exciton material 2PPOXBZ was designed and synthesized. • The hole mobility of 2PPOXBZ reached 2.56 × 10−3 cm2 V−1 s−1. • Doped deep red OLED device achieved an EQE up to 7.52% with CIE (0.67, 0.33). [ABSTRACT FROM AUTHOR]

Herein, we propose a simple and feasible design for regulating the excited state properties and achieving balanced carrier mobility of the HLCT blue emitter. The nondoped OLED base on 3PCZPBO with the LE state dominates the qHLCT state and the high-balanced carrier mobilities demonstrate excellent electroluminescent performance with high efficiency, low driving voltage, and low roll-off. [Display omitted] • A series of benzoxazole-based blue emitters have been designed and synthesized. • All emitters have qHLCT features and 3PCZPBO realizes balanced carrier mobility. • Non-doped devices achieve high-efficiency emissions in the range of 395–452 nm. • A tactic for adjusting the HLCT and carrier mobility of blue emitters is proposed. Carrier mobilities of emitter layer materials are crucial for the efficiency and efficiency stability of non-doped organic light-emitting diodes (OLEDs). However, realizing high and balanced carrier mobilities, particularly electron mobility for organic materials, remains challenging. Herein, we design four blue-emissive quasi-equivalent hybridized local and charge transfer (HLCT) benzoxazole-phenylcarbazole derivatives, and discover the influence of three molecular designs (meta -linkage, phenyl-increasing and large group substitution) on OLED performance. Phenyl group insertion can enhance π-conjugation and regulate the locally excited (LE) component of the HLCT state, which not only contributes to high photoluminescent quantum yield (PLQY) but also maintains the charge-transfer (CT) property for the triplet utilization in OLED. More importantly, π-conjugation enhancement contributes to more regular aggregation, increasing carrier mobilities. Meanwhile, a large group (e.g., tert -butyl) substitution can hinder aggregation and afford bad carrier mobilities between adjacent molecules. As a result, we realize balanced and boosted carrier mobilities (hole: 2.64 × 10−6 cm2 V−1 s−1; electron: 2.40 × 10−5 cm2 V−1 s−1) in the non-doped OLED of 2-(4′-(9-phenyl-9H-carbazol-3-yl)-[1,1′-biphenyl]-4-yl)benzo[d]oxazole (3-PCZPBO), corresponding to the highest external quantum efficiency (EQE max) of 7.1% with low efficiency rolling-off. This study provides a valuable strategy for the design of efficient blue emitters. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two benzoxazole-based pure/deep blue emitters with bar-like structure are developed. • Rich C–H∙∙∙π interactions impart superior mobilities and optical properties of emitters. • Nondoped device achieves deep-blue emission with CIE y coordinate of 0.048 at 427 nm. • Deep-blue device demonstrates a best-in-class EQE of 8% for similar light colors. • Both blue OLEDs exhibit low efficiency-roll at a high luminance of 10000 cd m−2. Developing a high-performance nondoped deep-blue luminescent material that meets the substantial demand of high-definition organic light-emitting diodes (OLEDs) is significant and challenging. Herein, two highly efficient bar-like pure-blue and deep-blue materials, namely, PIPMePBO and PIPDMePBO, respectively, are designed and synthesized. Rigid planar phenanthroimidazole (PI) and benzoxazole (PBO) moieties are linked to construct a conjugated structure for a regulated aggregation pattern in both single crystals and evaporation films. This approach helps enhance and balance their carrier mobilities for excellent, stable OLED efficiency. Furthermore, different numbers of steric hindrance methyl groups are added to the π-conjugated bridge. This not only avoids potential conjugation quenching and aggregation redshift but also benefits the excited-state constructions for the regulation of blue purity. Results show that the double-methyl-substituted PIPDMePBO, with a moderate charge-transfer excited state, shows nondoped deep-blue electroluminescence with Commission Internationale de l'Eclairage coordinates of (0.156, 0.048). Its maximum luminescence is 12212 cd m−2. Remarkably, the nondoped OLED based on PIPDMePBO exhibits an excellent external quantum efficiency of 8.0%, with an efficiency roll-off of only approximately 12%, even at 10000 cd m−2. These findings are among the best for nondoped deep-blue fluorescent OLEDs with similar light colors. [ABSTRACT FROM AUTHOR]

Deep red (DR) and near-infrared (NIR) fluorescent emitters are often plagued by design difficulties due to the strong intramolecular interaction. Herein, two new DR and NIR molecules, 4-(7-(10-ethyl-10 H -phenoxazin-3-yl)benzo[c][1,2,5]thiadiazol-4-yl)- N,N -diphenylaniline (TPAC2) and 4-(9-(10-ethyl-10 H -phenoxazin-3-yl)naphtho[2,3-c][1,2,5]thiadiazol-4-yl)- N,N -diphenylaniline (TPANZC2), characteristic with hybrid local and charge transfer were achieved via iteration with a theoretical combined experimental method. Both emitters realized the reverse intersystem crossing (RISC) via the hot exciton channel. As results, the non-doped organic light-emitting diodes (OLEDs) of TPAC2 and TPANZC2 achieved the maximum external quantum efficiency (EQE max) of 2.4% at 680 nm and 1.1% at 755 nm, respectively. Both conspicuous upward EQE curves demonstrated excellent resistance to efficiency roll-off. The ternary co-doping system further unleashed the potential in NIR emission, the co-doped device with 5 wt% TPANZC2 achieved an EQE of 4.6% with emission at 724 nm, which is among the best results of HLCT-NIR fluorescent OLEDs to date. [Display omitted] • Iterative strategy reasonably achieved deep red to NIR emission. • The co-doped NIR device achieved an EQE of 4.6%, is the best HLCT-NIR OLED performance to date. • EQE loss only 2.4% and 0.8% at 90% maximum luminescence. [ABSTRACT FROM AUTHOR]

The properties of excited states of emitters play an important role in OLEDs. How to obtain balanced hybrid localized charge transfer (HLCT) state by reasonably designing molecules is still a challenge. Herein, three HLCT states D-π-A type blue fluorophores with different LE/CT hybrid degree were designed and synthesized, namely 3,6-di-tert-butyl-9-(4-(6-(4-(4,5-diphenyl-4 H -1,2,4-triazol-3-yl)phenyl)pyren-1-yl)phenyl)-9 H carbazole (DTPCZPYTZ), 3,6-di-tert-butyl-9-(4-(4-(4-(4,5-diphenyl-4 H -1,2,4-triazol-3-yl)phenyl)naphthalen-1-yl)phenyl)-9 H -carbazole (DTPCZNATZ) and 3,6-di-tert-butyl-9-(4''-(4,5-diphenyl-4 H -1,2,4-triazol-3-yl)-[1,1':4′,1″-terphenyl]-4-yl)-9 H -carbazole (DTPCZPHTZ). DTPCZPHTZ achieved quasi-equivalent hybrid local and charge-transfer (HLCT) excited state and efficient "hot-exciton" channel, the non-doped deep-blue device based on DTPCZPHTZ has an electroluminescence emission peak (λ EL) of 427 nm with Commission International de L'Eclairage (CIE) of (0.157, 0.037), the maximum external quantum efficiency (EQE) is up to 5.7% and the efficiency roll-off is only 5% (under 1000 cd m−2), which is outstanding in the reported deep-blue emitters. This study proved that the quasi-equivalent hybrid HLCT state is beneficial to improving device performance. This work provides a flexible and convenient method for fine-tuning the excited states of emitters, by changing the number of benzene rings in the intermediate π bridge, the degree of LE/CT hybridization can be adjusted. Finally, quasi-equivalent hybrid deep-blue luminescent emitter and highly efficient non-doped deep-blue OLED is obtained. [Display omitted] • Construction of quasi-equivalent hybrid local and charge-transfer (HLCT) excited state and hot exciton channels. • Efficient non-doped deep-blue OLED with EQE up to 5.7% and CIE (0.157, 0.037). • Highly Suppressed efficiency roll-off of only 1%–5% at 1000 cd m−2. [ABSTRACT FROM AUTHOR]

This work provides a flexible and convenient method for fine-tuning the excited states of emitters, precise "surgery" was performed by targeting the molecular excited states through locally large twisted conformations, and finally obtained excellent hot exciton red emitters and high efficiency non-doped deep-red OLEDs. [Display omitted] • Deep-red emitters construct idea utilizing locally large twisted conformation. • Three emitters display hot exciton and aggregation-induced emission properties. • Breakthrough EQEs of hot exciton non-doped red devices up to 5.3% and 6%. The precise regulation of excited state is a challenge to emitters for achieving highly efficient non-doped deep-red electroluminescence (EL). Herein, we used triphenylamine and phenoxazine as donors and benzo[c][1,2,5]thiadiazole as an acceptor to construct a hot exciton skeleton. Then chemically modified the phenoxazine by locally large twisted conformation to obtain N , N -diphenyl-4-(7-(10-phenyl-10H-phenoxazin-3-yl)benzo[c][1,2,5]thiadiazol-4-yl)aniline (TPAPH), 4-(7-(10-(4-ethoxyphenyl)-10 H -phenoxazin-3-yl)benzo[c][1,2,5]thiadiazol-4-yl)- N , N -diphenylaniline (TPAPHOC2), and 4-(3-(7-(4-(diphenylamino)phenyl)benzo[c][1,2,5]thiadiazol-4-yl)-10 H -phenoxazin-10-yl)benzonitrile (TPAPHCN), thereby achieving excited state perturbation. As a result, three emitters exhibited aggregation-induced emission enhancement and hybridized local and charge transfers characteristics based on photophysical experimentals. In EL, the TPAPH-, TPAPHOC2-, and TPAPHCN-based non-doped devices achieved deep-red emission with Commission International de L'Eclairage coordinates of (0.68, 0.32), (0.69, 0.31), and (0.66, 0.34) and with emission peaks at 660, 669, and 647 nm, respectively. The maximum external quantum efficiencies were 5.3%, 3.7%, and 6.0%, respectively. The results of this study not only realize the non-doped deep-red OLEDs with high performance but also indicate that the presence of locally large twisted conformation presented an efficient manner for exploring precise excited state tuning for fluorescent emitter. [ABSTRACT FROM AUTHOR]

Anthracene is a traditional blue-fluorescence group with excellent electron-transporting ability and high fluorescence quantum efficiency. With the increasingly wide application of anthracene derivatives in electroluminescence (EL) fields, how the molecule is constructed becomes particularly critical owing to the natural flat conformation of the anthracene group, which quenches fluorescence in the aggregated state. In this study, we designed and synthesized a simple donor–acceptor-type molecule by hybridizing anthracene with triazole [3-(4-(anthracen-9-yl)phenyl)-4,5-diphenyl-4 H -1,2,4-triazole (ANTZ)]. In this molecule, anthracene acts as an electron donor, and the triazole unit with a twisting spatial construction and electron-withdrawing ability can not only inhibit the flat-stacking effect between anthracene and anthracene but also demonstrate carrier-transport ability to mimic anthracene. The optimized nondoped, deep-blue Device I using ANTZ as an emitter exhibits deep-blue-fluorescence emission with smaller Commission Internationale de I'Eclairage (CIEy) coordinates of 0.13, a maximum external quantum efficiency (EQE) of 3.3%, and a low-efficiency roll-off of 3.0%, which was a significant improvement relative to Device II using a traditional 2-methyl-9,10-bis(naphthalen-2-yl)anthracene emitter. The superior EL properties of Device I suggest its effectiveness as a molecular design for deep-blue emitters based on anthracene derivatives. [Display omitted] • A novel molecule was designed by hybridizing anthracene with triazole. • Non-doped ANTZ-based device exhibits a negligible efficiency roll-off of 3 %. • Deep-blue ANTZ-based device shows a small CIEy value. • This method is promising in the exploration of deep-blue OLED fields. [ABSTRACT FROM AUTHOR]

Although considerable progress has been achieved in organic electroluminescence (EL) fields based on aggregation-induced emission (AIE) effect emitters, highly efficient and multifunctional blue fluorophores with the AIE effect are still limited. In this work, a simple blue fluorescent molecule 3,4-diphenyl-5-(4ʹ-(1,2,2-triphenylvinyl)-[1,1ʹ-biphenyl]-4-yl)-4 H -1,2,4-triazole (TPETAZ) with the evident properties of AIE has been designed and synthesized based on tetraphenylethylene–triazole hybrid. The AIE-active molecule TPETAZ can act as both intrinsic blue light-emitting and electron-transporting layer in organic light-emitting diodes (OLEDs). Nondoped Device I with TmPyPB layer exhibits a maximal external quantum efficiency (EQE) of 2.4%, a maximum luminance (L) of 1020 cd m−2, and maximal EL emission peak of 468 nm. Even though Device II without a TmPyPB layer exhibited excellent performance, the maximal EQE was observed to be 2.0%, indicating a decrease of only 18% when compared with that of Device I. However, the maximal EL emission peak remains almost unchanged (~470 nm). Furthermore, efficient doped Device III can be obtained by doping the host with TPETAZ as the blue light-emitting material. A maximal EQE of 4.1% was obtained, which was greater than those of Devices I and II by 42% and 52%, respectively; this can be attributed to the effective recombination of electron and hole carriers. This work provides a valuable strategy for designing highly efficient multifunctional blue EL AIE-active fluorophores, which have significant potential for practical applications. [Display omitted] • An AIE-active blue-light emitter (TPETAZ) is designed and synthesized. • TPETAZ shows obvious aggregation-induced emission properties. • TPETAZ exhibits a photoluminescence quantum yield of 75.7% in film. • Non-doped OLED without electron-transporting material exhibits an EQE max of 2.0%. [ABSTRACT FROM AUTHOR]

• Pure-blue emitter PICNAnCz with "hot-exciton" mechanism is synthesized. • Nondoped OLED exhibits an EL peak at 448 nm with CIE coordinates of (0.16, 0.11). • "Hot-exciton" mechanism OLED device with EQE up to 9.05% and low roll-off of 13%. "Hot-exciton" fluorescent materials can efficiently convert triplet excitons into singlet excitons through a path from high-lying triplet excited states (T n , n > 1) to singlet excited states (S m , m ≥ 1). The fast reverse intersystem crossing (RISC) process of the hot-exciton channel promotes a high exciton utilization efficiency (EUE) and reduces the efficiency roll-off (η roll-off) caused by the accumulation of low-lying triplet excitons (T 1). Herein, a pure-blue-emitting molecule, PICNAnCz, exhibiting hot-exciton fluorescent emission is proposed. The optimized PICNAnCz-based nondoped organic light-emitting diode (OLED) device achieves a high external quantum efficiency of 9.05% corresponding to a large EUE of 87% and a low η roll-off of 13%, achieving both high efficiency and a small η roll-off. The maximum current efficiency and power efficiency of the nondoped device are 9.07 cd A−1 and 5.76 lm W−1, respectively. The nondoped device shows a novel blue electroluminescence (EL) emission with a peak wavelength of 448 nm and Commission Internationale de l'Eclairage coordinates of (0.16, 0.11). These results are among the best reported for hot-exciton blue-emitting materials for nondoped blue fluorescent OLEDs. The excellent EL performance is attributed to the nanosecond-scale RISC process from the high-lying triplet excited state (T 2) to the lowest singlet excited state (S 1). [ABSTRACT FROM AUTHOR]

Limited by the energy gap law and large conjugate structures, red organic light-emitting diodes (OLEDs) have long been criticized for their efficiency problems. The aggregation-induced emission (AIE) effect and the reverse intersystem crossing process can lead to high photoluminescent quantum yields (PLQYs) and high exciton utilization efficiency (EUE), two key objectives for obtaining efficient OLEDs. In this work, we chose benzothiadiazole as the acceptor (A) and triphenylamine and phenothiazine as the donors (Ds) to design and synthesize a D–A–D red fluorescent molecule, PBTPA. Results of systematic photophysical measurements indicated PBTPA to exhibit AIE trending, manifesting as aggregation-induced enhanced emission and the characteristics of hybridized local and charge transfer (HLCT) states. These features facilitated high solid-state luminescence efficiency and high exciton utilization to be achieved. A non-doped device fabricated using PBTPA displayed a red electroluminescence peak at 656 nm, corresponding to the Commission International de L'Eclairage coordinates of (0.65, 0.32), and an external quantum efficiency of 1.62%. By calculation, the EUE reached a value of 50%. According to the results of theoretical calculations, the effective hot exciton channel between the second triplet (T 2) and the lowest singlet (S 1) was responsible for the high EUE. This EUE value is relatively good for this type of red OLEDs. Evidence indicates that combining AIE and HLCT has excellent potential to aid the discovery of new-generation highly efficient red OLEDs. Image 1 • A novel D–A–D-type red fluorescent emitter, PBTPA, was designed and synthesized. • It displayed aggregation-induced emission and hybridized local and charge transfer. • Non-doped OLED had 50% EUE, efficient hot exciton channel, low-efficiency roll-off. [ABSTRACT FROM AUTHOR]

Tetraphenylethene (TPE) is a star group exhibiting an excellent aggregation-induced emission (AIE) effect. Although significant progress has been made in the field of organic electroluminescence (EL) based on TPE-substituted emitters, highly efficient and high-color-purity TPE-substituted blue fluorophores with the AIE effect are still very rare. In this paper, a simple and effective molecule— N -phenyl- N -(4-(1-phenyl-1 H -phenanthro[9,10-d]imidazol-2-yl)phenyl)-4′-(1,2,2-triphenylvinyl)-[1,1′-biphenyl]-4-amine (TPETPAPI)—was designed and synthesized using triphenylamine (donor), phenanthroimidazole (acceptor), and tetraphenylethylene (AIE generator). In tetrahydrofuran solution, the molecule emits little light and the quantum efficiency is low (1.3%); however, the fluorescence is enhanced in the film (73%), exhibiting remarkable AIE properties, thus enabling TPETPAPI to be used in future applications in organic light-emitting diodes. The nondoped device exhibits a low turn-on voltage of 3.0 V, a maximum luminance of 10780 cd m−2, maximum current efficiency of 12.20 cd A−1, and maximum power efficiency of 11.95 lm W−1, with an EL peak at 476 nm. TPETPAPI exhibits the most impressive EL performance reported to date for a TPE-substituted blue fluorophore with AIE' characteristics. A new AIE-active blue fluorescent emitter (TPETPAPI) with simple structure is designed and facilely synthesized by a star group TPE-substituted. The non-doped device emitted 476 nm bright blue emission with a maximum luminance of 10780 cd m−2, a maximal current efficiency of 11.95 cd A−1, maximum EQE of 6.05%. The results representing the most efficient (EL max ≤ 480 nm) blue OLED based on the TPE-substituted AIE-active fluorescent molecule reported thus far. Image 1 • A new AIE-active blue fluorescent emitter (TPETPAPI) is designed and synthesized. • The TPETPAPI exhibits aggregation-induced emission (AIE) properties. • The non-doped OLED exhibits excellent device performance with an EQE of 6.05%. [ABSTRACT FROM AUTHOR]

Excited state characteristics of a new generation of organic luminescent materials play a key role in determining their luminescent properties. As a special excited species, the hybridized local and charge-transfer (HLCT) excited state is a promising strategy to achieve blue emission and high photoluminescence quantum yield. Herein, a novel donor-acceptor fluorophore, namely 2-phenyl-5-(10-(4-(1,2,2-triphenylvinyl)phenyl)-10 H -phenothiazin-3-yl)-1,3,4-oxadia-zole (TPEPO), is designed and synthesized as an efficient blue organic light-emitting diode (BOLED) material. Remarkably, the external quantum efficiencies of the nondoped device with TPEPO as an emitter was as high as 6.62% and radiative exciton ratio was also high, i.e., approximately 36%–55%, indicating that the developed BOLED exhibits the highest efficiency that has been reported so far for a BOLED based on phenothiazine as the donor material. This work provides a comprehensive understanding of the relation between the excited state characteristics and electroluminescence properties and a valuable strategy for the design of a new generation of blue chromophores with phenothiazine as the donor. A new blue fluorescent emitter (TPEPO) with simple structure is designed and facilely synthesized. The nondoped device emitted 480 nm bright blue emission with a maximum luminance of 17007 cd m−2, a maximal current efficiency of 15.86 cd A−1, maximum EQE of 6.62% as well as a high radiative exciton ratio of ∼55% based on HLCT. The results representing the most efficient blue OLED based on phenothiazine as the donor material reported thus far. Image 1 • A new blue molecule was constructed with phenothiazine as the strong donor and oxadiazole as the acceptor. • The EQE of the non-doped Blue OLED is greater than 6.0%. • Highly efficient non-doped Blue OLED was obtained with Hybridized Local and Charge-transfer Excited State. [ABSTRACT FROM AUTHOR]