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Dye‐sensitized down‐conversion nanoparticles (DCNPs) can significantly enhance photon absorption, bridging the gap of narrow and weak absorption cross‐section of lanthanide (Ln) ions, thus fundamentally prompting their near‐infrared (NIR) emission. However, the ideal strategy for utilization of both the singlet and triplet energy of the dyes is hindered by the nanostructures and the dependence on the heavy atom effect. Herein, thermally activated delayed fluorescence (TADF) dye is utilized with a small singlet‐triplet energy gap as the absorption antenna, achieving a 733 fold emission enhancement. This strategy facilitates efficient intersystem crossing (ISC) and reverse intersystem crossing (RISC) processes, enabling effective energy transfer from singlet (S1) and triplet (T1) excitons to emitted energy levels of Er3+. Combining highly Erbium‐doped nanoparticles, the water‐dispersed AD‐sensitized system shows excellent hydrodynamic stability and photostability. This innovative approach marks the first report of TADF dye‐sensitized Ln nanosystems, offering a new direction for photo conversion technology. [ABSTRACT FROM AUTHOR]

Constructing folded molecular structures is emerging as a promising strategy to develop efficient thermally activated delayed fluorescence (TADF) materials. Most folded TADF materials have V‐shaped configurations formed by donors and acceptors linked on carbazole or fluorene bridges. In this work, a facile molecular design strategy is proposed for exploring sandwich‐structured molecules, and a series of novel and robust TADF materials with regular U‐shaped sandwich conformations are constructed by using 11,12‐dihydroindolo[2,3‐a]carbazole as bridge, xanthone as acceptor, and dibenzothiophene, dibenzofuran, 9‐phenylcarbazole and indolo[3,2,1‐JK]carbazole as donors. They hold outstanding thermal stability with ultrahigh decomposition temperatures (556–563 °C), and exhibit fast delayed fluorescence and excellent photoluminescence quantum efficiencies (86 %–97 %). The regular and close stacking of acceptor and donors results in rigidified molecular structures with efficient through‐space interaction, which are conducive to suppressing intramolecular motion and reducing reorganized excited‐state energy. The organic light‐emitting diodes (OLEDs) using them as emitters exhibit excellent electroluminescence performances, with maximum external quantum efficiencies of up to 30.6 %, which is a leading value for the OLEDs based on folded TADF emitters. These results demonstrate the proposed strategy of employing 11,12‐dihydroindolo[2,3‐a]carbazole as bridge for planar donors and acceptors to construct efficient folded TADF materials is applicable. [ABSTRACT FROM AUTHOR]

Achieving high‐efficiency and narrowband deep‐blue emission is of great significance for organic light‐emitting diodes (OLEDs). Herein, a novel selenium‐containing spiro‐acridine donor, DspiroSe, is designed for constructing highly efficient blue emitters. The spiro structure of DspiroSe contributes to suppressed aggregation‐caused quenching, while the selenium atom provides heavy‐atom effect. By attaching DspiroSe to a multiple resonance skeleton with different linkage strategies, two isomeric emitters sSeDDBN and PsSe‐DABNA are obtained, which show promise as candidates for blue OLEDs. Note that the different linkage methods of DspiroSe enable tuning of the emission spectrum from sky‐blue to deep‐blue, with PsSe‐DABNA demonstrating exceptional deep‐blue emission characterized by a full‐width at half‐maximum of 18 nm and a peak wavelength of 445 nm in solution. Both sSeDDBN and PsSe‐DABNA exhibit high photoluminescence quantum yields exceeding 90% in films, and OLEDs using them as emitters achieve maximum external quantum efficiencies (EQEmax) of 26.5% and 14.6%, respectively. By utilizing a TADF assistant host, the EQEmax further increases to 28.5% for sSeDDBN and 19.1% for PsSe‐DABNA. Notably, PsSe‐DABNA based OLEDs exhibit excellent color purity with Commission Internationale de l'Eclairage coordinates of (0.145, 0.052), closely approaching the BT.2020 blue standard. [ABSTRACT FROM AUTHOR]

The exploration of circularly polarized luminescence is important for advancing display and lighting technologies. Herein, by utilizing isomeric molecular engineering, a novel series of chiral molecules are designed to exploit both thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP) mechanisms for efficient luminescence. The cooperation of a small singlet‐triplet energy gap, moderate spin‐orbital coupling (SOC), and large oscillator strength enables efficient TADF emission, with photoluminescence quantum yields exceeding 90 %. By altering the symmetry of molecular structures, it is demonstrated that the intrinsic electronic SOC and vibrational SOC effects can be greatly enhanced to facilitate RTP emission. Notably, through modulating simultaneous TADF and RTP emissions, single‐molecule white emission is successfully achieved. Accordingly, the TADF‐based organic light‐emitting diode (OLED) achieves a maximum external quantum efficiency up to 30 %, representing exceptional performance of non‐aromatic amine‐based emitters. Furthermore, the first single‐molecule white OLED based on TADF and RTP dual‐emissive chiral material is developed, establishing a benchmark for the development of advanced display and lighting technologies. [ABSTRACT FROM AUTHOR]

Developing thermally activated delayed fluorescence (TADF)‐active silver clusters with near‐unity quantum efficiency is of practical importance in cutting‐edge optoelectronic devices, but remains a tremendous challenge due to the difficulty of de novo synthesis and uncertainty of properties. Herein, we demonstrate a lattice modulation on parent TADF‐ active silver cluster, achieving TADF‐driven photoluminescence quantum yield (PLQY) from 12 % to near‐unity. Systematic experimental and calculated results reveal that the lattice modulation effectively lowers the singlet‐triplet splitting (ΔEST) from 718 to 549 cm‐1, thereby facilitating thermally activated reverse intersystem crossing: T5→S5, leading to extremely efficient TADF by surpassing both phosphorescence and non‐radiative decay, thus boosting the near‐unity PLQY. Such high PLQY is extremely rare in the TADF‐active silver clusters and even in the whole noble‐metal clusters. This research showcases an unparalleled example of lattice modulation to realize near unity PLQY of TADF‐active silver clusters. [ABSTRACT FROM AUTHOR]

Due to higher exciton energy, the deep‐blue organic light‐emitting diodes (OLEDs) are the most challenging among trichromatic emitters. In this work, three novel blue emitters with multi‐resonance (MR) effects are reported based on N,N,5,9‐tetraphenyl‐5,9‐dihydro‐5,9‐diaza‐13b‐boranaphtho[3,2,1‐de]anthracen‐7‐amine (PAB) skeleton, incorporating fluorine and methyl groups. Compound 2FPAB and MePAB exhibit ultra‐pure deep‐blue emission peaks at 436 and 448 nm respectively. The device based on MePAB achieves a maximum external quantum efficiency of 19.8% with an ultralow CIEy value of 0.046 and a full‐width‐at‐half‐maximum (FWHM) of 29 nm in the bottom emitting device. Additionally, the peripheral cladding of fluorine atoms extends the conjugation framework and slightly enhances the electron acceptance character of the boron atom at the ortho‐position. This leads to a redshift in the emission spectrum and enhanced photoluminescence quantum yield (PLQY) of up to 93% for MePABF. Furthermore, the potential application of MePAB as a deep‐blue sensitizer for MePABF is examined by fabricating a TADF‐sensitized‐TADF (TST) device. The results show a significantly reduced efficiency roll‐off and improved device performance, with a maximum external quantum efficiency (EQEmax) of 25.1% and a FWHM of 29 nm. [ABSTRACT FROM AUTHOR]

Triplet generation and control are widely studied in high‐energy scintillating materials, owing to their critical roles in thermally activated delayed fluorescence (TADF) and energy‐transfer processes. However, X‐ray excited inorganic scintillators, such as Cs2ZrCl6, present various defect traps in the self‐trapped exciton states. Hence, the mobility of the hot carriers that participate in scintillating dynamics is disorderly, and they may contribute to TADF or suppress the TADF pathway. This study prepares a series of Cs2ZrCl6: x%m‐MTDATA (x% = 0%–10%) organic–inorganic hybrid scintillators to achieve tunable photoluminescence (PL) and radioluminescence (RL) through a directional energy‐transfer pathway. This work highlights the different scintillating carrier dynamics of Cs2ZrCl6: x%m‐MTDATA under ultraviolet or X‐ray excitation. The introduction of m‐MTDATA into Cs2ZrCl6 could increase the trap depths and ensure thermal quenching under X‐ray excitation, rather than inducing thermal activation, resulting in a weak X‐ray excited afterglow output and fast RL decay time. These findings provide a paradigm for future research on organic–inorganic hybrid X‐ray scintillators, opening new opportunities for detecting high‐energy radiations. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) materials with the through‐space charge transfer (TSCT) effects can provide a useful approach to efficiently utilize dark state triplet excitons through an efficient reverse intersystem crossing process. TSCT‐TADF emitters PCzoTrz‐ICz with small ∆EST values and high photoluminescence quantum yield is designed and synthesized using common acceptor triazine, donor 3,6‐diphenylcarbazole and Indolo[3,2,1‐jk]carbazole which is a rigid π‐conjugated group with high triplet state and high thermal stability. The doped‐organic light‐emitting diodes using PCzoTrz‐ICz as emitters exhibit high tolerance to host with different polarity and charge transport properties, and PCzoTrz‐ICz doped devices in 2,8‐bis(diphenylphosphoryl)dibenzofuran even realizes a maximum external quantum efficiency (EQEmax) of 32.5% and maximum current efficiency (CEmax) of 74.1 cd A−1, which is higher than EQEmax of 28.1% and CEmax of 64.8 cd A−1 of PCzoTrz. Moreover, PCzoTrz‐ICz can be used as highly efficient sensitizers for narrow band blue emitter of v‐DABNA, and achieves more than EQEmax of 33.3%, maximum luminance of 26,291 cd m−2, CEmax of 42.7 cd A−1 and blue index of 237 cd A−1 CIEy−1. [ABSTRACT FROM AUTHOR]

Recently, an ever‐growing interest has been paid on organic single‐molecule white light‐emitting materials for effective white organic light‐emitting diodes (WOLEDs). However, subject to Kasha's rule, photons can only be emitted from the lowest excited state and thus panchromatic or dual emissions are extremely forbidden, which results in a certain challenge in achieving white emission. Herein, a strategy of synergetic carbonyl and heptagonal structure is proposed for organic single‐molecule white light emission and demonstrated by TAO/TABO/TA2O organic luminescent materials that are modified on aryl ketones/amine fragments. Among them, due to the robust intermolecular interactions triggered by synergetic carbonyl and heptagonal structure, TA2O exhibits vibrant monomer and dimer photoluminescence with dual thermally activated delayed fluorescence (TADF) characteristics. As a result, the first single‐molecule dual‐TADF WOLED based on the synergetic system is successfully fabricated with an external quantum efficiency of 7.2%. This study not only expands the scope of carbonyl and heptagonal structure for novel optoelectronic properties and applications but also opens new avenues for the development of efficient single‐molecule WOLEDs with dual TADF mechanisms. [ABSTRACT FROM AUTHOR]

Herein, a design strategy is explored for thermally activated delayed fluorescence (TADF) materials by employing the meta‐linkage of the spiral‐donors 10H‐spiro[acridine‐9,9'‐thioxanthene] (DspiroS) and 10',10'‐dimethyl‐10H,10'H‐spiro[acridine‐9,9'‐anthracene] (DspiroAc) to the robust acceptor 2,4,6‐triphenyl‐1,3,5‐triazine (TRZ). Two distinct TADF materials, m‐DspiroS‐TRZ and m‐DspiroAc‐TRZ, exhibiting unique photophysical properties and performance characteristics were synthesized. Interestingly, even subtle modifications in the molecular architecture can significantly impact the organization of materials in their aggregated state, thereby governing photophysical properties and inducing corresponding alterations in photoelectric characteristics. Notably, m‐DspiroS‐TRZ exhibits superior photophysical properties and exciton dynamics data, achieving a high photoluminescence quantum yield (PLQY) value of up to 95.9% and a rapid reverse intersystem crossing (RISC) rate (풌푹푰푺푪) of 1.0 × 106 s−1. This positions m‐DspiroS‐TRZ as a potentially excellent terminal emissive and sensitizing host material, inspiring further exploration of its applications in electroluminescence. Consequently, TADF organic light‐emitting device (TADF‐OLED) and TADF‐sensitized fluorescence (TSF‐OLED) based on m‐DspiroS‐TRZ have achieved maximum external quantum efficiencies (EQEs) of 31.8% and 34.5%, respectively, demonstrating the significant versatile potential of m‐DspiroS‐TRZ. [ABSTRACT FROM AUTHOR]

Hydrogen bonds (HBs), prevalent strong interactions in organic compounds, can effectively constrain single bond rotation, leading to rigid planar configurations. This rigidity enhances emission efficiency and narrows the emission spectrum of luminescent materials. Recent advances have leveraged HBs to advance high‐performance donor‐acceptor thermally activated delayed fluorescence (TADF) materials. However, their application in multi‐resonance (MR) TADF emitters remains limited. We herein developed MR‐TADF emitters incorporating intramolecular hydrogen bonds (IHBs) with pyrimidine as the HB acceptor. The rigid planar conformation induced by IHBs significantly improved photoluminescence quantum yield, extended emission wavelength, reduced full‐width at half‐maximum, and decreased non‐radiative decay rates for BN‐2Pm compared to BN‐5Pm. Devices based on BN‐2Pm achieved a maximum external quantum efficiency of 36.5 %, a current efficiency of 102.3 cd A−1, a power efficiency of 84.6 lm W−1, and Commission Internationale de l’Éclairage (CIE) coordinates of (0.18, 0.71). In contrast, BN‐5Pm exhibited lower values: 14.6 %, 36.8 cd A−1, 27.6 lm W−1, and (0.12, 0.57), respectively. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) materials have emerged as a promising avenue for developing efficient and stable blue organic light‐emitting diodes (OLEDs) without incorporating heavy metals. Among the numerous donor‐acceptor architectures explored, the carbazole (Cz) and benzonitrile (BN) combination has demonstrated exceptional potential for blue OLED applications. Herein, we delve into the recent advances in TADF materials based on the Cz‐BN framework, with a particular focus on design strategies to accelerate exciton dynamics and improve material stability through kinetic and thermodynamic optimization. Eventually, challenges associated with the Cz‐BN systems in blue OLEDs, as well as prospective research directions that could unlock the full potential of this intriguing category of materials, are also discussed. [ABSTRACT FROM AUTHOR]

Polycyclic heteroaromatics (PHAs) are a highly versatile class of functional materials, especially applicable as efficient luminophores in organic light‐emitting diodes (OLEDs). Those constructed by tethered phenyl surrounding the main group center attract extensive attention due to their excellent OLED device performance. However, the development of such a class of emitters is often limited to boron, nitrogen‐doped π‐conjugated heterocycles. Herein, we proposed a novel kind of blue emitter by constructing a donor‐acceptor molecular configuration, utilizing a dual sulfone‐bridged triphenylamine (BTPO) core and mono/di‐diphenylamine (DPA) substituents. The twisted D−A molecular structures and appropriate donor strength facilitate the effective separation of natural transition orbitals, endowing the emitters with charge‐transfer dominant hybridized local and charge‐transfer characteristics for the excited states. Both BTPO‐DPA and BTPO‐2DPA own small S1–T1 splitting energy, thus demonstrating blue thermally activated delayed fluorescence. The more symmetrical structure and enhanced CT features brought by additional DPA moiety confer BTPO‐2DPA with a shorter delayed fluorescence lifetime, a higher fluorescence quantum yield and narrower emission. Therefore, BTPO‐2DPA based OLED devices exhibit superior blue electroluminescence performance, with external quantum efficiencies reaching 12.31 %. [ABSTRACT FROM AUTHOR]

Exploring efficient thermally‐activated delayed fluorescence materials having maximum external quantum efficiencies (ηext,maxs) exceeding 30 % for organic light‐emitting diodes (OLEDs) still remains challenging because it generally requires efficient reverse intersystem crossing (RISC), high photoluminescence quantum yield (ΦPL), and large optical out‐coupling efficiency (Φout) simultaneously. Herein, two green aggregation‐induced delayed fluorescence (AIDF) luminogens, named XTCz‐2 and XTCz‐3, are designed and constructed by using xanthone (XT) as electron acceptor and phenylcarbazole‐substituted carbazole as donors. XTCz‐2 and XTCz‐3 exhibit distinguished advantages of high thermal stability (439–560 °C), excellent ΦPLs (84–88 %) and fast RISC rates (1.9×105–4.2×105 s−1), and prefer horizontal dipole orientation and thus have high Φouts. Consequently, they can achieve the state‐of‐the‐art electroluminescence (EL) performances with ηext,maxs of up to 35.0 %. Moreover, XTCz‐3 is selected as a sensitizer for sky‐blue multi‐resonance delayed fluorescence emitter in hyperfluorescence OLEDs, providing narrow EL spectra and excellent ηext,maxs of up to 33.8 % with low efficiency roll‐offs. The splendid comprehensive performances demonstrate the significant application potential of these AIDF luminogens as both light‐emitting materials and sensitizers for OLEDs. [ABSTRACT FROM AUTHOR]

Intermolecular charge transfer (inter‐CT) is commonly considered to quench luminescence in molecular aggregates, especially for near‐infrared (NIR) emission. Herein, by elaborate comparison of π‐bridge effects in donor/acceptor (D/A) molecules, it is disclosed that a π‐bridge is essential in D/A molecule to involve inter‐CT in aggregates for inducing desired thermally activated delayed fluorescence (TADF) and largely suppressing non‐radiative decays, and importantly, electron‐donating π‐bridge is critical to maximize radiative decay for inter‐CT dominated emission by effective electronic coupling with bright intramolecular charge transfer (intra‐CT) for high‐efficiency NIR emission. As a proof‐of‐concept, TPATAP with thienyl as π‐bridge realized prominent photoluminescence quantum yields of 18.9% at 788 nm in solid films, and achieved record‐high maximum external quantum efficiencies of 4.53% at 785 nm in devices. These findings provide fresh insight into interplay between inter‐CT and intra‐CT in molecular aggregates and open a new avenue to attenuate the limitation of energy gap law for developing highly efficient NIR emitters and improving the luminescent efficiency of various inter‐CT systems, such as organic photovoltaic, organic long persistent luminescence, etc. [ABSTRACT FROM AUTHOR]

Multi‐resonant thermally activated delayed fluorescence (MR‐TADF) emitters have attracted strong interest for organic electroluminescent devices due to their high photoluminescence quantum yield (ΦPL) and narrowband emission. These properties are also crucial for high‐performance biological probes, especially red emitters. Orange and red MR‐TADF emitters, PhDPA‐DiKTa and MeODPA‐DiKTa, are designed by decorating the DiKTa core with di([1,1′‐biphenyl]‐4‐yl)amine and bis(4‐methoxyphenyl)amine, respectively. As 5 wt.% doped films in 1,3‐di(9H‐carbazol‐9‐yl)benzene (mCP), PhDPA‐DiKTa emits at λPL of 617 nm, while MeODPA‐DiKTa emits at λPL of 655 nm. Both show delayed fluorescence, with delayed lifetimes, τd, of 658.4 and 249.2 µs, respectively. Water‐dispersible glassy organic dots (g‐Odots) based on these materials are prepared by encapsulating them and mCP host into an amphiphilic DSPE‐PEG2k polymer. Both families of g‐Odots showed a deeper red emission and enhanced ΦPL compared to the corresponding 5 wt.% doped films in mCP (λPL = 618 nm, ΦPL = 77% for PhDPA‐DiKTa g‐Odots, λPL = 663 nm, ΦPL = 38% for MeODPA‐DiKTa g‐Odots). The TADF character of the emitters is conserved in the g‐ODots, with τd of 203.9 µs for PhDPA‐DiKTa g‐Odots and 131.6 µs for MeODPA‐DiKTa g‐Odots. These MR‐TADF g‐Odots are successfully demonstrated as biological imaging probes of HeLa cells. [ABSTRACT FROM AUTHOR]

We prepared thermally activated delayed fluorescence (TADF) emitter dyads, NI‐PTZ, NI‐PTZ‐2Br and NI‐PSeZ, with naphthalimide (NI) as electron acceptor and 10H‐phenothiazine (PTZ) or 10H‐phenoselenazine (PSeZ) as electron donor to study the heavy‐atom effect on the intersystem crossing (ISC) and reverse ISC (rISC) in the TADF emitters. The delayed fluorescence lifetimes of the dyads containing heavy atoms ( τDF ${{\tau }_{{\rm D}{\rm F}}}$ =5.9 μs for NI‐PSeZ and τDF ${{\tau }_{{\rm D}{\rm F}}}$ =16.5 μs for NI‐PTZ‐2Br, respectively) are longer than the heavy atom‐free counterpart NI‐PTZ ( τDF ${{\tau }_{{\rm D}{\rm F}}}$ =2.0 μs). Nanosecond transient absorption (ns‐TA) spectral study and the time‐resolved electron paramagnetic resonance (TREPR) spectra show the presence of both 3LE and 3CS states. These findings represent solid experimental evidences for the spin‐vibronic coupling mechanism of TADF. Moreover, the ns‐TA spectra show that the heavy atoms don't have a significant effect since the lifetime of the triplet transient species (1.3 μs for NI‐PTZ) is not shortened in their presence (4.5 μs for NI‐PSeZ and 5.3 μs for NI‐PTZ‐2Br). These results show that the previously claimed heavy‐atom effect on rISC and TADF is not a universal principle. The femtosecond transient absorption (fs‐TA) spectra of the compounds indicate the occurrence of fast charge separation within 1–2 ps, and the charge recombination is slow (>4 ns) [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) materials hold promise for optoelectronic applications. Among various design strategies, through‐space charge transfer (TSCT) systems offer the potential for enhanced performance. However, the relationship between molecular configuration and TSCT properties remains unclear compared to traditional through‐band charge transfer materials. In this study, we investigated the influence of spatial configuration on TSCT features and electronic properties of triplet excited states in these TSCT materials. By manipulating the spatial arrangement between donor and acceptor segments using different spiro skeletons, a series of TSCT materials (DMB2‐DMB5) was synthesized. Together with the parent molecule, DM‐B, these materials exhibited completely different TADF characteristics, demonstrating the impact of spatial arrangements on their optoelectronic properties. Thus, the external quantum efficiency of these materials ranged from as high as 28.0 % (DMB2) to as low as 3.6 % (DMB5) due to variations in their TADF characteristics. Our findings highlight the significance of spatial configuration, beyond distance alone, in influencing TSCT properties when donor and acceptor segments are sufficiently close. This insight provides valuable guidance for developing advanced TSCT materials and advancing TADF systems with improved performance and functionality. [ABSTRACT FROM AUTHOR]

Achieving efficient circularly polarized white organic light‐emitting diode (CP‐WOLED) remains a significant challenge. In this study, a proof‐of‐concept for realizing CP‐WOLED is proposed using an electroplex emission strategy between a chiral thermally activated delayed fluorescence (TADF) emitter and hole‐transporting material. A series of chiral polymers (R/S)‐E‐x (x = 0.02, 0.05, and 0.1) are designed and prepared via random copolymerization of a chiral chromophore and styrene moiety, which shows typical TADF character. The neat film of (R/S)‐E‐0.1 presents distinct chiroptical properties with a dissymmetry factor (|glum|) of 2.8 × 10−3. Notably, solution‐processable, single‐emitting‐layer CP‐WOLEDs are fabricated using these chiral polymers in combination with 1,1‐bis[(di‐4‐tolylamino)phenyl]cyclohexane (TAPC) as the emitter, achieving a record maximum external quantum efficiency of 15.1% and Commission Internationale de lʹeclairage coordinate of (0.36, 0.40). Importantly, these CP‐WOLEDs exhibit an impressive |gEL| value of 2.4 × 10−3. This research provides a straightforward and effective strategy for the realization of high‐performance CP‐WOLED. [ABSTRACT FROM AUTHOR]

Aiming to design new efficient organic triplet emitters, here a new electron‐accepting moiety 11,13‐dihydro‐12H‐dibenzo[a,c]imidazo[4,5‐i]phenazin‐12‐one (BIPO) are reported. Three new BIPO derivatives containing long alkyl chains, namely DBIPO (acceptor only), DBIPOBr (acceptor containing bromine atoms), and DBIPOAc with acridan moieties in a donor‐acceptor‐donor configuration, are designed and investigated. Efficient room temperature phosphorescence (RTP) is detected for the three compounds, stemming from a high‐lying (anti‐Kasha type) triplet emission occurring in the acceptor moiety. Additionally, the tetrahydrofuran‐ and dichloromethane DBIPOAc solutions show (i) a dual‐band photoluminescence profile stemming from anti‐Kasha emissions from high‐lying charge‐transfer (1CT) and locally excited (1LE) states, and (ii) a thermally activated delayed fluorescence (TADF) from the same high‐lying 1CT state. Importantly, DBIPOAc doped in rigid nonpolar polymer Zeonex simultaneously exhibits both TADF and RTP, with the emission quantum yield reaching 69.6%. Due to these properties, the BIPO derivatives constitute promising candidates as multi‐functional new emitters for the preparation of active layers of electroluminescent devices and optical oxygen/pressure sensors. The reasons for these interesting properties are discussed in detail. [ABSTRACT FROM AUTHOR]

Molecular emitters that combined thermally activated delayed and circularly polarized fluorescence (CP‐TADF) is of paramount importance for the next generation of displays. While most efforts have thus far focused on covalent donor and acceptor CP‐TADF emitters, a novel strategy based on chiral exciplexes has recently emerged. In this context, we present the synthesis and chiroptical properties of four new CP‐TADF exciplexes, involving two distinct C2‐symmetric bicarbazole systems and two terpyridine‐based derivatives, which serve as the chiral donor and achiral acceptor units, respectively. These exciplexes exhibit CP‐luminescence, with intensity dependent on both the chiral donor and achiral constituents, resulting in emission dissymmetry factors reaching up to 10⁻2 in the thin‐film solid state. Additionally, small singlet‐triplet gaps (∆EST ≤ 0.1 eV) have been measured, leading to TADF characteristics with a photoluminescence quantum yield of 20% for the most efficient emitter, which is also successfully used in non‐optimized organic lightemitting diodes (OLEDs). Interestingly, these chiral exciplexes allow us to explore the impact of the locally‐excited (LE) state of the chiral donor on overall exciplex emission, particularly in relation to the intensity of polarized emission—potentially highlighting a key factor in the design of this type of bimolecular CP‐TADF emitter. [ABSTRACT FROM AUTHOR]

In the past, considerable effort are focused on advancing blue organic light‐emitting diodes (OLEDs) based on 1,3‐bis(N‐carbazolyl)benzene (mCP). To enhance and stabilize the device performance in vacuum‐processed OLEDs, it is essential to optimize the thermally stable organic materials constituting the emitting layer. The proposed novel carbazole derivative, Ad‐mCP, is designed and synthesized as a host material for blue thermally activated delayed fluorescence OLEDs, which are ideal for vacuum processing. Ad‐mCP exhibits a high glass transition temperature and triplet energy (T1), making it highly compatible with the blue dopant 2,11,14‐tri‐tert‐butyl‐N,N,5‐tris(4‐(tert‐butyl)phenyl)−5H‐5,8b‐diaza‐15b‐borabenzo[a]naphtho[1,2,3‐hi]aceanthrylen‐7‐amine emitter. The incorporation of a rigid adamantane unit into the carbazole group modifies the molecular structure of mCP, preserving crucial photophysical properties, such as T1,while enhancing the morphological and thermal stability of the host material in its film state. Moreover, the spatially hindered molecular structure of Ad‐mCP improves the photoluminescent quantum yield of the emissive layer and enhances charge balance, crucially contributing to the overall efficiency of the OLEDs. As a result, the exceptional performance of Ad‐mCP as a host material for OLEDs resulted in a remarkably high maximum external quantum efficiency of 29.9%, demonstrating superior stability in efficiency even after thermal annealing compared to mCP devices. [ABSTRACT FROM AUTHOR]

Due to the extended conjugation along the polymeric backbone and the scarcity of suitable multi‐resonance (MR) emitting units for polymerization, precisely adjusting the colors of MR‐thermally activated delayed fluorescence (MR‐TADF) conjugated polymers to green and red region remains to be a formidable challenge. Herein, this work develops a series of green MR‐TADF polymers for the first time by attaching MR emitting moiety as pendant to an acceptor triphenyltriazine while simultaneously embedding acceptor moiety into polycarbazole backbone. Benefitting from the enhanced intramolecular charge transfer (ICT) interaction by introducing acceptor on the para‐carbon position of boron (B) atom of the MR unit, as well as extended conjugation along backbone, all polymers exhibit red‐shifted emissions with emission peaks of 505–517 nm and full‐width at half maximums (FWHMs) of below 48 nm compared to the pendant bluish‐green MR unit peaking at 484 nm. The solution‐processed devices based on these polymers exhibit excellent performances with maximum quantum efficiency (EQE) of 22.2%, emission peak at 511 nm and FWHM of 44 nm, which represents the state‐of‐the‐art performance among the MR‐TADF polymer‐based narrowband OLEDs. [ABSTRACT FROM AUTHOR]

Photon‐upconversion (PUC) processes in organic molecular systems, such as triplet‐triplet upconversion and hot‐band absorption, are promising technologies for future energy harvesting. Although these processes can generate high‐energy excitons compared to excitation energy, a PUC process with a high yield and no energy loss has not been established and, therefore, is highly desired. Here, we propose an alternative PUC mechanism that uses reverse intersystem crossing on thermally activated delayed fluorescence (TADF) molecules. This process combines a triplet sensitizer and a TADF molecule, generating a triplet in the former and transferring it to the latter. Specifically, the triplet energy transfer from Ir(ppy)3 (sensitizer) to CzBSe (TADF) results in anti‐Stokes emission with an anti‐Stokes energy of 0.18 eV. We found that the triplet energy transfer rate strongly depends on the triplet radiative decay rate of TADF molecules and the difference in Gibbs energy between the energy acceptor and donor. Our findings will contribute to understanding triplet energy transfer dynamics in organic energy donor‐acceptor systems and will lead to various applications, such as future optical cooling systems. [ABSTRACT FROM AUTHOR]

Thermal activation process utilizes environmental thermal energy to help supplement energy for the nonspontaneous energy‐consuming upconversion physical transitions with positive free energy change (ΔG>0). Reverse intersystem crossing (rISC) and hot band absorption are two kinds of thermal activation transitions. Thermally activated delayed fluorescence (TADF) materials with rISC have significantly propelled advancements in organic semiconductors. Hot band absorption, enables anti‐Stokes photoluminescence, offering a promising route for efficient photon upconversion. In this work, we constructed a crystal consisting of a donor‐acceptor type TADF molecule, DPQ‐DPAC, demonstrating dual thermal activation properties of hot band absorption with a notable 0.1 eV anti‐Stokes shift emission and proficient TADF performance. Only in the crystal TADF efficiency facilitates and the photoluminescence quantum yield elevates to an impressive 90.8 %. Combining the extended absorption spectrum, these enhancements collectively realize anti‐Stokes photoluminescence in crystal. Experimental and theoretical results on the DPQ‐DPAC crystal indicate optimizations in its conformational and vibrational modes, resulting in enhancements to its properties. This finding provides insight into crafting organic materials with thermally activated functionalities and contributes to fully exploiting the potential of organic materials, further advancing versatile materials applications. [ABSTRACT FROM AUTHOR]

Highly efficient blue organic light‐emitting diodes (OLEDs) generally exhibit inferior color purity or large full width at half maximum (FWHM). Therefore, emitting materials with simultaneously high efficiency and small FWHM in the deep‐blue region are challenging to construct. To address this, hybrid multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters are designed by combining boron‐based MR‐TADF materials, which exhibit small FWHM and high efficiency, with indolo[3,2,1‐jk]carbazole (ICz)‐based MR‐TADF materials, which exhibit high color purity. Two hybrid MR‐TADF emitters are synthesized by hybridizing ICz with a boron‐based MR‐TADF core to prepare deep‐blue OLEDs with high efficiency and high color purity. The hybrid MR‐TADF emitter exhibits a maximum external quantum efficiency of 28.7% and deep‐blue emission at 454 nm with an FWHM of 25 nm, and CIEy of 0.053, nearly satisfying the BT 2020 color standard. The device efficiency achieved in this work is one of the highest values reported for the blue OLEDs with the CIEy close to 0.05. [ABSTRACT FROM AUTHOR]

The prototypical example of a (cyclo)phane, [2.2]paracyclophane (PCP), has proven to be a versatile stereogenic moiety within the design of circularly polarized thermally activated delayed fluorescence (CP‐TADF) emitters; however, the exploration of other cyclophanes within CP‐TADF emitter design has been largely neglected. Here, a comparative study of the photophysical and optoelectronic properties of two cyclophane emitters, (1,7)tBuCzpPhTrz and its isomer (1,4)tBuCzpPhTrz, is presented. The carbazolophane‐triazine compound (1,7)tBuCzpPhTrz, obtained via an unprecedented intramolecular rearrangement, is the first example of a planar chiral TADF emitter deviating from the PCP scaffold. Significant geometrical change of the enclosed carbazole in (1,7)tBuCzp results in an attenuation of the donor strength, while the merits of rigidity and steric bulk remain. In particular, the full width at half maximum (FWHM) of the photoluminescence spectrum in toluene of (1,7)tBuCzpPhTrz is reduced by 34% and blue‐shifted by 20 nm compared to that of (1,4)tBuCzpPhTrz. In doped films, the compounds reach high photoluminescence quantum yields (ΦPL) of 91 and 81%, respectively. The chiroptical properties reveal dissymmetry factors |gPL| of up to 5 × 10−4. These results demonstrate the impact of the cyclophane for the development of CP‐TADF materials and add to the currently limited scope of available planar chiral donors. [ABSTRACT FROM AUTHOR]

Multiresonance thermally activated delayed fluorescence (MR‐TADF) emitters with high color purity in virtue of their inherent narrowband emission have received great interest in organic light‐emitting diodes (OLEDs). However, it remains a big challenge to develop the ultrapure blue MR‐TADF emitters with high efficiency. In this work, a novel "dual‐MR‐core" strategy is proposed by connecting two parent N‐B‐O‐skeletons with non‐conjugate 9‐position substituted fluorene linkages for high efficient deep‐blue MR‐TADF emitters, namely H‐FOBN and Me‐FOBN, which possess the highly twisted structure with suppressed aggregation. Finally, the vacuum‐deposited deep‐blue OLED exhibits excellent external quantum efficiency (EQE) of 25.1% with small full width at half maximum (FWHM) of 28 nm, as well as CIE of (0.14, 0.08). Furthermore, owing to enhanced solubility, the solution‐processed deep‐blue OLED based on Me‐FOBN shows EQE of 11.3%, with small FWHM of 32 nm and CIE of (0.14,0.09). These outstanding performances confirm that this "dual‐MR‐core" strategy provides a feasible approach to develop high efficient ultrapure blue MR‐TADF emitters. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) emitters with a high horizontal orientation are highly essential for improving the external quantum efficiency (EQE) of organic light‐emitting diodes; however, pivotal molecular design strategies to improve the horizontal orientation of solution‐processable TADF emitters are still scarce and challenging. Herein, a phenyl bridge is adopted to connect the double TADF units, and generate a dimerized TADF dendrimer, D4CzBNPh‐SF. Compared to its counterpart with a single TADF unit, the proof‐of‐the‐concept molecule not only exhibits an improved horizontal dipole ratio (78 %) due to the π‐delocalization‐induced extended molecular conjugation, but also displays a faster reversed intersystem crossing rate constant (6.08×106 s−1) and a high photoluminescence quantum yield of 95 % in neat film. Consequently, the non‐doped solution‐processed device with D4CzBNPh‐SF as the emitter achieves an ultra‐high maximum EQE of 32.6 %, which remains at 26.6 % under a luminance of 1000 cd/m2. Furthermore, when using D4CzBNPh‐SF as a sensitizer, the TADF‐sensitized fluorescence device exhibits a high maximum EQE of 30.7 % at a luminance of 575 cd/m2 and a full width at half maximum of 36 nm. [ABSTRACT FROM AUTHOR]

Developing highly efficient pure‐blue organic light‐emitting diodes (OLEDs) that meet the stringent BT.2020 standard by using multi‐resonance thermally activated delayed fluorescence (MR‐TADF) materials has long been a formidable challenge. In this study, a strategy is demonstrated for high‐performance blue MR‐TADF emitters by gradually decorating the MR framework with alkyl groups, and subsequently introducing a diarylamino group at the para‐position of boron atom. The proof‐of‐concept molecule, IPrBN‐mCP, exhibits a narrowband deep‐blue emission peaking at 452 nm, with a very narrow full‐width at half maximum (FWHM) of 19 nm in solution, and a remarkably high photoluminescence quantum yield (PLQY) approaching unity in doped films. As a result, OLEDs based on IPrBN‐mCP achieve not only a high maximum external quantum efficiency (EQEmax) of 33.4% but also ultrapure blue emission with a Commission Internationale de L'Eclairage (CIE) y value of 0.046, fully satisfying the BT.2020 blue standard. This represents the first OLED example fully meeting the rigorous color requirements of the BT.2020 blue standard while simultaneously achieving an EQE exceeding 30%. [ABSTRACT FROM AUTHOR]

Multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters offer natural advantages for creating power‐efficient, wide‐color‐gamut OLEDs. However, current green MR‐TADF emitters face challenges in simultaneously achieving high color purity and efficient reverse inter‐system crossing (RISC), leading to suboptimal device performance. In this study, we propose a synergistic molecular design approach that combines π‐extension and peripheral locking to address these challenges. This approach allows for the construction of quadruple borylated MR‐TADF emitters that not only deliver precisely tuned pure‐green emission with a narrow full width at half maximum (FWHM) of 15 nm, but also exhibit close‐to‐unity quantum yield, rapid RISC, and optimal horizontal dipole orientation. The resulting sensitizer‐free OLED approaches the BT.2020 standard with CIE coordinates of (0.18, 0.74) and demonstrates impressive external quantum efficiency (EQE) of 36.6 % at maximum and 31.8 % at 1000 cd m−2. Additionally, the device shows good operational stability, with a lifetime (LT80) of 485 hours at an initial luminance of 1000 cd m−2. This study hence offers a promising molecular design strategy that effectively enhances the comprehensive OLED performance. [ABSTRACT FROM AUTHOR]

Exploring possible strategy to balance the radiative decay and reverse intersystem crossing (RISC) are of great significance in thermally activated delayed fluorescent (TADF) emitters for enabling both high efficiency and low efficiency roll‐off. Herein, by introducing a multi‐resonance (MR) type acceptor, two TADF emitters featuring hybridized short‐range charge transfer (SRCT) and long‐rang charge transfer (LRCT) are designed. LRCT‐dominate photoluminescent nature is maintained with a short delayed lifetime of 1.5–3.4 µs. While the incorporated SRCT accelerates the radiative decay. Consequently, both emitters demonstrate remarkable electroluminescent performance with maximum EQE (EQEmax) of 40.8% for IT‐BO and 39.0% for IA‐BO, respectively, along with ultra‐high luminance of up to 120 000 cd m−2. More encouragingly, both emitters can enable small efficiency roll‐off with a minimum value of only 4%, highlighting the significance of enhanced kr in suppressing the roll‐off. Moreover, when served as sensitizers, both compounds can also endow excellent performances with EQEmax ≈38%. This work presents an innovative approach by hybridizing SRCT and LRCT for developing practical TADF emitters. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) emitters potentially can provide organic light‐emitting diodes with 100% internal quantum efficiency by harvesting triplet excitons. Generally, TADF emitters are small molecules that are not applicable for solution processability. The addition of tert‐butyl groups to the periphery of TADF emitters has proven to improve their solubility in various organic solvents, reduce aggregation‐induced quenching, and enhance the photoluminescence quantum yield (PLQY). This article studies the photophysical influence of the tert‐butyl group attached to an emitter with a carbazole acceptor and a triazine donor. The resulting t3CzTrz‐F is a blue–green TADF emitter, in which the addition of a tert‐butyl group increases the rate of reverse intersystem crossing (rISC), while simultaneously decreasing the nonradiative decay rate substantially. In addition, dilution of t3CzTrz‐F in a host matrix in film results in an enhanced PLQY, which is associated with a decrease in the nonradiative decay constant, while there is no change in the rISC rate. Through a solid‐state NMR study, the change in rISC and nonradiative rate upon tert‐butylation by enlarged intermolecular spacing and reduced vibrational and rotational freedom is rationalized, resulting in improved photophysical performance. [ABSTRACT FROM AUTHOR]

Organic light‐emitting diodes (OLEDs) employing multi‐resonance (MR) emitters have attracted much attention due to their high luminescent efficiency and color purity, however, the development of deep‐blue multi‐resonance OLEDs is hindered by the lack of suitable sensitizers. Here a novel design strategy is reported for thermally activated delayed fluorescence sensitizer with high reverse intersystem crossing (kRISC) and radiative transition (kR) rate by regulating atom distribution of a spatially‐aligned carbazole donor/diphenylpyrimidine acceptor structure to manipulate through‐space charge transfer (CT) process. It is found that diphenylpyrimidine acceptor with 1,3‐position nitrogen atoms is un‐conjugated to bridging phenyl moiety by the conjugation node of pyrimidine, while the acceptor with 1,5‐position nitrogen atoms is conjugated to bridging phenyl through conjugation site, opening through‐bond CT pathway via bridging phenyl besides through‐space CT from spatial donor‐acceptor interactions. As a result, the sensitizer with 1,5‐position nitrogen atoms exhibits enhanced oscillator strength by 3.5 folds and accelerated kR of 3.57 × 107 s−1, while keeping high kRISC of 4.03 × 106 s−1 and high singlet (S1) state (2.88 eV). Solution‐processed OLEDs using the sensitizer and deep‐blue multi‐resonance emitter exhibit efficient narrowband electroluminescence with CIE coordinates of (0.14, 0.13) and EQEmax of 15.6%, representing the state‐of‐the‐art device performance for deep‐blue multi‐resonance OLEDs by solution process. [ABSTRACT FROM AUTHOR]

Advanced multiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters with high efficiency and color purity have emerged as a research focus in the development of ultra‐high‐definition displays. Herein, we disclose an approach to modulate the charge‐transfer excited states of MR emitters via intramolecular covalent bond locking. This strategy can promote the evolution of strong intramolecular charge‐transfer (ICT) states into weak ICT states, ultimately narrowing the full‐width at half‐maximum (FWHM) of emitters. To modulate the ICT intensity, two octagonal rings are introduced to yield molecule m‐DCzDAz‐BNCz. Compounds m‐CzDAz‐BNCz and m‐DCzDAz‐BNCz exhibit bright light‐green and green fluorescence in toluene, with emission maxima of 504 and 513 nm, and FWHMs of 28 and 34 nm, respectively. Sensitized organic light‐emitting diodes (OLEDs) employing emitters m‐CzDAz‐BNCz and m‐DCzDAz‐BNCz exhibit green emission with peaks of 508 and 520 nm, Commission Internationale de L'Eclairage (CIE) coordinates of (0.12, 0.65) and (0.19, 0.69), and maximum external quantum efficiencies (EQEs) of 30.2 % and 32.6 %, respectively. [ABSTRACT FROM AUTHOR]

The development of polymer‐based persistent luminescence materials with color‐tunable organic afterglow and multiple responses is highly desirable for applications in anti‐counterfeiting, flexible displays, and data‐storage. However, achieving efficient persistent luminescence from a single‐phosphor system with multiple responses remains a challenging task. Herein, by doping 9H‐pyrido[3,4‐b]indole (PI2) into an amorphous polyacrylamide matrix, a hierarchical dual‐mode emission system is developed, which exhibits color‐tunable afterglow due to excitation‐, temperature‐, and humidity‐dependence. Notably, the coexistence of the isolated state and J‐aggregate state of the guest molecule not only provides an excitation‐dependent afterglow color, but also leads to a hierarchical temperature‐dependent afterglow color resulting from different thermally activated delayed fluorescence (TADF) and ultralong organic phosphorescence (UOP) behaviors of the isolated and aggregated states. The complex responsiveness based on the hierarchical dual‐mode emission can serve for security features through inkjet printing and ink‐writing. These findings may provide further insight into the regulated persistent luminescence by isolated and aggregated phosphors in doped polymer systems and expand the scope of stimuli‐responsive organic afterglow materials for broader applications. [ABSTRACT FROM AUTHOR]

Glassy organic dots (g‐Odots) are an emerging class of luminescent nanoparticles that offer enhanced photostability, superior brightness, and modular tunability compared to other commonly employed nanoparticles. In the last several years, they have been used as bioimaging probes for single‐ and multi‐photon cellular imaging, exhibiting low cytotoxicity even after several days. While they are emerging as promising materials for use in biological applications, g‐Odots face several key challenges before their use can become widespread. In this concept, we outline the state of the literature on g‐Odots and highlight a few ways in which their design and use can be improved upon. [ABSTRACT FROM AUTHOR]

The π‐conjugated macrocyclic emitters with thermally activated delayed fluorescence (TADF) characteristics have attracted widespread attention in the field of organic electroluminescence (EL) materials due to their unique geometries and excellent luminescence performance. Despite the significant impact of conjugation length and cavity dimensions on molecular conformation, the influence of these factors on the excited‐state properties remains understudied. Herein, we formulated a strategy aimed at modulating the conformation of TADF macrocyclic molecules containing aniline as the donor (D) unit, and triazine as the acceptor (A), linked in D−A and D‐π‐A alternative macrocyclic construction (MC‐TNT and MC‐TST). Corroborated by experimental and theoretical analyses, the compact and conformationally twisted MC‐TNT exhibits efficient blue luminescence in crystalline state, facilitating EL at high doping concentrations with maximum external quantum efficiency (EQEmax) of 13.9 %, leading the field of blue macrocyclic emitters. Notably, MC‐TST with π‐bridge and flat conformation, demonstrates diminished Coulombic repulsion, achieving nearly 100 % photoluminescence quantum yield and superior horizontal dipole orientation of 85 % in 5 wt % doped films, and the corresponding device‘s EQEmax reaches record‐high 32.7 % within the TADF macrocyclic domain. [ABSTRACT FROM AUTHOR]

Achieving the concurrent manifestation of thermally activated delayed fluorescence (TADF) and aggregation‐induced emission (AIE) within a single molecular system is highly sought after for organic light‐emitting diodes (OLEDs), yet remains rare. In this study, we present a novel TADF‐AIE dye, named PQMO‐PXZ, which has been designed, synthesized, and systematically characterized. Our comprehensive investigation, which includes structural analysis, theoretical calculations, and optical studies, evaluates the potential of PQMO‐PXZ for integration into OLEDs. Unlike existing azaryl‐ketone‐based emitters, PQMO‐PXZ exhibits red‐shifted emission and enhanced luminescence efficiency, due to its rigid structure and strong intramolecular charge transfer characteristics. Significantly, PQMO‐PXZ demonstrates pronounced AIE properties and TADF with a short delayed lifetime. When utilized as the emissive core, OLED devices based on PQMO‐PXZ achieve a respectable external quantum efficiency of up to 11.8 % with minimal efficiency roll‐off, underscoring PQMO‐PXZ's promise as a highly efficient candidate for OLED applications. [ABSTRACT FROM AUTHOR]

Already known molecules which exhibit good electrochemiluminescence (ECL) efficiencies and high photoluminescence quantum yields (PLQY) have been structurally modified in order to increase their performance. The followed strategy is to stiffen the structures to limit the rotational and vibrational freedom degrees and favour radiative decay processes once excited. Molecules under investigation consist of donor‐acceptor systems in which the acceptor fraction is a benzonitrile with an imidazole in para position, while the donor fraction consists of four diphenylamine (NPh2) or 3,6‐di(tert‐butyl)‐9H‐carbazole (t‐BuCz) groups in the remaining positions on the central benzene ring. Therefore, in order to stiffen these systems and restrict the intramolecular rotations (RIR), the imidazole in the para position has been replaced with more extended π‐systems, i. e., benzimidazole and phenanthro[9,10‐d]imidazole. The restriction of the intramolecular rotation can be clearly observed by 1H NMR analysis. We expected to observe an increase in ECL efficiency and PLQY with the rigidity. Surprisingly, we observed a generally opposite trend: molecules with the smallest imidazole fraction showed the best performance in ECL and higher PLQY. Notably, NPh2 derivatives with benzimidazole and phenanthro[9,10‐d]imidazole showed an hypsochromic shift of the emission spectra with concomitant increase of the PLQY as the solvent polarity increases. [ABSTRACT FROM AUTHOR]

In this work, we synthesize a series of push–pull compounds bearing naphthalimide as the electron acceptor and tetraphenylethylene (TPE)/triphenylamine (TPA)/phenothiazine (PTZ) as the electron rich/electron donor units. These moieties are arranged in highly conjugated quadrupolar structures. The structure–property relationships are investigated through a joint experimental time–resolved spectroscopic and computational TD–DFT study. The femtosecond transient absorption and fluorescence up–conversion experiments reveal ultrafast photoinduced intramolecular charge transfer. This is likely the key factor leading to efficient spin–orbit CT–induced intersystem crossing for the TPA– and PTZ–derivatives as well as to small singlet–to–triplet energy gap. Consequently, evidence for a delayed fluorescence component is found together with the main prompt emission in the fluorescence kinetics both in solution and in thin film. The weight of the Thermally Activated Delayed Fluorescence (TADF) is greatly enhanced when these fluorophores are used as guests in solid–state host matrices. TADF is interestingly revealed in the orange–red region of the visible. Such long wavelength emission is here observed with surprisingly large fluorescence quantum yields, thanks to the conjugation enhancement achieved in these newly synthesized structures relative to previous studies. Our findings may be thus promising for the future development of efficient third generation TADF–based OLEDs. [ABSTRACT FROM AUTHOR]

Organic light‐emitting diodes (OLEDs) are promising lighting solutions for sustainability and energy efficiency. Incorporating thermally activated delayed fluorescence (TADF) molecules enables OLEDs to achieve internal quantum efficiency (IQE), in principle, up to 100 %; therefore, new classes of promising TADF emitters and modifications of existing ones are sought after. This study explores the TADF emission properties of six designed TADF emitters, examining their photophysical responses using experimental and theoretical methods. The design strategy involves creating six distinct types of a donor‐acceptor (D−A) system, where tert‐butylcarbazoles are used as donors, while the acceptor component incorporates three different functional groups: nitrile, tetrazole and oxadiazole, with varying electron‐withdrawing character. Additionally, the donor‐acceptor distance is adjusted using a phenylene spacer, and its influence on TADF functionality is examined. The clear dependency of an additional spacer, inhibiting TADF, could be revealed. Emitters with a direct donor‐acceptor connection are demonstrated to exhibit TADF moderate emissive behavior. The analysis emphasizes the impact of charge transfer, singlet‐triplet energy gaps (ΔEST), and other microscopic parameters on photophysical rates, permitting TADF. Among the emitters, TCz‐CN shows optimal performance as a blue‐green emitter with an 88 % photoluminescence quantum yield (PLQY) and fast rate of reversible intersystem crossing of 2×106 s−1 and 1×107 s−1, obtained from time‐resolved photoluminescence (TRPL) experiment in PMMA matrix and quantum mechanical calculations, respectively. This comprehensive exploration identifies molecular bases of superior TADF emitters and provides insights for future designs, advancing the optimization of TADF properties in OLEDs. [ABSTRACT FROM AUTHOR]

Reported herein is the first example of a copper‐mediated C─H cyclization of heterocycles to construct structurally diverse carbonyl‐bridged triphenylamine compounds with multiple resonance thermally activated delayed fluorescence (TADF) characteristics. The one‐pot synthesis method exhibits a broad substrate scope and opens a new avenue for rapidly screening high‐performance organic TADF luminescent materials. Novel organic TADF single‐molecule white‐light material 5g with anti‐Kasha dual‐emission character is the first time developed herein and shows a Commission Internationale de l’Eclairage (CIE) coordinate of (0.33, 0.35) in the thin film, and can be used to fabricate robust and low cost organic white light‐emitting diodes (LED). Furthermore, the anti‐Kasha dual‐emission material 5g is fabricated as water‐dispersed nanoparticles (NPs)NPs, which can be efficiently endocytosed into the HeLa cells and dual emission imaging in living cells, and be used in two‐channel emission intensity ratio imaging to observe the intercellular structure. [ABSTRACT FROM AUTHOR]

Although multi‐resonance thermally activated delayed fluorescent (MR‐TADF) emitters simultaneously achieve high color purity and high efficiency in organic light‐emitting devices (OLEDs), MR‐TADF‐based OLEDs suffer from severe efficiency roll‐off and lifetime issues for practical application. To overcome these issues, a key solution is hyper OLED technology sensitized by TADF or phosphorescent emitters. In this study, a series of π‐extended phenoxazine‐based asymmetric MR‐TADF emitters for long lifetime, low‐power consumption, and narrow emission band green OLEDs is developed. As a sensitizer, a well‐known phosphorescent emitter is used, fac‐tris(2‐phenylpyridinato‐C2,N)iridium(III) [Ir(ppy)3]. Consequently, these MR‐TADF emitters achieve hyper OLEDs with a power efficiency of 150 lmW−1, an external quantum efficiency of 27%, and a long lifetime LT95 of over 3000 h at high brightness of 1000 cdm−2. These performances are among the best in scientific literature. [ABSTRACT FROM AUTHOR]

In the development of organic light‐emitting diodes (OLEDs) with high efficiency and minimal efficiency roll‐off, fast reverse intersystem crossing (RISC) in multi‐resonance thermally activated delayed fluorescence (MR‐TADF) materials is critical. The RISC process is typically hindered by insufficient spin‐orbital coupling (SOC). Incorporating heavy atom selenium into the MR‐TADF structure has the potential to enhance SOC through the heavy atom effect. However, the specific placement of selenium within the molecule results in different enhancements of SOC, with the detailed interplay between these factors yet to be elucidated. The introduction of a selenium‐containing moiety, phenoxaselenine, into the MR‐TADF structure at different substituted positions is undertaken, revealing that the molecule with 3‐substituted phenoxaselenine exhibits faster RISC transition and a significant increase in SOC between higher triplet excited states and S1 state, compared to the molecule with 2‐substituted phenoxaselenine. Significantly reduced efficiency roll‐off is achieved for the narrow‐band emission OLEDs based on the molecule with 3‐substituted phenoxaselenine owing to the enhanced heavy atom effect, giving an impressive external quantum efficiency above 20% even under 10 000 cd m−2 in the corresponding OLED device. These results underscore the potential of strategic heavy atom effect manipulation in MR‐TADF materials for efficient spin‐flipping. [ABSTRACT FROM AUTHOR]

Organic scintillators, pivotal in security and medical applications, face challenges due to limited X‐ray absorption and exciton utilization. Herein, a novel class of organic scintillators is introduced, named guest‐induced thermally activated delayed fluorescence (TADF) within supramolecular macrocycles via host‐guest through‐space charge transfer (TSCT). Four co‐crystals are obtained through orthogonal crystallizations involving calix[3]acridan (C[3]A) and calix[3]phenothiazine (C[3]P) macrocycles as hosts, along with 1,2‐dicyanobenzene (DCB) and 4‐bromo‐1,2‐benzenedicarbonitrile (BrDCB) as guests. Interestingly, DCB@C[3]A and BrDCB@C[3]A co‐crystals exhibit strong host‐guest TSCT with reduced single‐triplet energy gap for efficient TADF emission, which leads to enhanced exciton utilization and X‐ray absorption, yielding radioluminescence intensities over 29 and 25 times higher than C[3]A. Similarly, substituting C[3]A with C[3]P, the obtained TADF co‐crystals also outperform C[3]P in scintillation performance. Additionally, the scintillation color of co‐crystals can be adjusted by varying the electron‐donating abilities of macrocycles and the electron‐accepting abilities of guests, offering a simpler color‐tuning mechanism than covalent‐bonded scintillators. Furthermore, the flexible film based on DCB@C[3]A exhibits promising application in X‐ray radiography, showcasing a high spatial resolution of 20 lp mm−1 @MTF = 0.77. The innovative strategy of fabricating organic scintillators via reversible non‐covalent interactions presents a novel solution for designing color‐tunable and high‐performance scintillators. [ABSTRACT FROM AUTHOR]

Benzophenone skeletons containing a carbonyl unit (O=C) have been widely used as electron acceptors in the thermally activated delayed fluorescence (TADF) materials. Herein, we present a novel molecular design concept for TADF materials by transitioning from a carbonyl to an amide (O=C−N) skeleton as the acceptor. The amide unit, compared to its carbonyl counterpart, offers a more stable electronic configuration. Leveraging this insight, we have developed a series of high‐performance TADF molecules based on benzoyl carbazole and carbazoline acceptors. These molecules exhibit exceptionally small singlet‐triplet energy gaps and pronounced aggregation‐enhanced emission properties, achieving photoluminescence quantum yields in neat films as high as 99 %. Consequently, these materials serve as efficient emitters in non‐doped organic light‐eimtting diodes (OLEDs), reaching a maximum quantum efficiency (EQEmax) of up to 26.0 %, significantly higher than the 17.0 % obtained with benzophenone acceptor‐based TADF molecules. Additionally, they have been used as TADF hosts in narrowband red fluorescent OLEDs, setting a record‐high EQEmax of 22.4 %. [ABSTRACT FROM AUTHOR]

A series of TADF‐active compounds: 0D chiral Ln−Ag(I) clusters L‐/D‐Ln2Ag28‐0D (Ln=Eu/Gd) and 2D chiral Ln−Ag(I) cluster‐based frameworks L‐/D‐Ln2Ag28‐2D (Ln=Gd) has been synthesized. Atomic‐level structural analysis showed that the chiral Ag(I) cluster units {Ag14S12} in L‐/D‐Ln2Ag28‐0D and L‐/D‐Ln2Ag28‐2D exhibited similar configurations, linked by varying numbers of [Ln(H2O)x]3+ (x=6 for 0D, x=3 for 2D) to form the final target compounds. Temperature‐dependent emission spectra and decay lifetimes measurement demonstrated the presence of TADF in L‐Ln2Ag28‐0D (Ln=Eu/Gd) and L‐Gd2Ag28‐2D. Experimentally, the remarkable TADF properties primarily originated from {Ag14S12} moieties in these compounds. Notably, {Ag14S12} in L‐Eu2Ag28‐0D and L‐Gd2Ag28‐2D displayed higher promote fluorescence rate and shorter TADF decay times than L‐Gd2Ag28‐0D. Combined with theoretical calculations, it was determined that the TADF behaviors of {Ag14S12} cluster units were induced by 4 f perturbation of Ln3+ ions. Specially, while maintaining ΔE(S1–T1) small enough, it can significantly increase k(S1→S0) and reduce TADF decay time by adjusting the type or number of Ln3+ ions, thus achieving the purpose of improving TADF for cluster‐based luminescent materials. [ABSTRACT FROM AUTHOR]

Deep‐red and near‐infrared emitters with twisted donor–acceptor (D–A) structures often exhibit suboptimal performance in organic light‐emitting diodes (OLEDs) due to constraints imposed by the energy gap law. In this work, a pure hydrogen carbon (PHC) host material named SBF‐DTP is purposefully tailored for deep‐red OLEDs. The excellent capacity of SBF‐DTP to support D–A type DR emitters effectively arises from its distinctive attributes: localized excitation states, 3D configuration, and low polarity. When employing SBF‐DTP as the host for the fluorescence emitter DCPA‐TPA and the thermally activated delayed fluorescence emitter APDC‐DTPA, doped films exhibit substantially enhanced photoluminescence quantum yields. This improvement leads to high‐efficiency OLEDs with external quantum efficiencies of 5.47% for DCPA‐TPA and 20.03% for APDC‐DTPA, respectively, which is about twice as high as the initial reports. This findings underscore the paramount significance of developing efficient host materials in the pursuit of high‐performance deep red and even near‐infrared OLEDs. [ABSTRACT FROM AUTHOR]

Developing highly efficient red/near‐infrared (NIR) thermally activated delayed fluorescence (TADF) materials is important for organic light‐emitting diodes (OLEDs). Here, two TADF emitters, APTT and APTI, which have the same D/A backbone but different attaching groups at acenaphtho‐[1,2‐b]pyrazine‐8,9‐dicarbonitrile (APDC) core, are reported. The appended regulating groups can not only suppress the D/A rotation due to the space confinement effects but also modulate the locally excited triplet state (3LE). The improved molecular rigidity suppresses the non‐radiative process, accounting for the improved photoluminescence quantum yields (PLQYs), while the modulated 3LE promotes the reverse intersystem crossing (RISC) process due to the high utilization efficiency of triplets. Consequently, both APTT and APTI demonstrate high PLQY and fast RISC process, thereby enhancing TADF efficiency. The doped devices based on APTT and APTI achieve maximum external quantum efficiency (EQEmax) values of 20.5% and 25.4% with emission peaks at 664 and 670 nm, respectively. The non‐doped devices of APTT and APTI achieve the EQEmax of 2.8% and 2.9% with emission peaks at 788 and 794 nm, respectively. Encouragingly, the non‐doped devices of APTI have set new records for near‐infrared TADF OLEDs based on the APDC core. This study provides an efficient approach to modulating the optoelectronic properties of highly efficient NIR TADF OLEDs. [ABSTRACT FROM AUTHOR]