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ABSTRACT Two polytriphenylamines (PTPAs) (P1 and P2) with aggregation induced emission (AIE)-active tetraphenylethylene side groups have been designed and successfully synthesized. Both polymers only faintly emit in dilute solution but show strong emission in aggregated state, meaning that they are AIE-active. The detection of 1,3,5-trinitrobenzene (TNB) vapors has been investigated by photoluminescence (PL) quenching in polymer films. High solid state quantum yields and donor-acceptor interactions of the electron-rich PTPA chains with the TNB analyte, hereby, induce a high sensing sensitivity, both for P1 and P2 films towards TNB vapor. Contacting thin P1 and P2 films with saturated TNB vapor, the PL intensity was quenched by 85% for P1 and 89% for P2 within 600 s, respectively. The sensing process is reversible, >90% of the PL is recovered, also after repeated cycling. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 53, 1753-1761 [ABSTRACT FROM AUTHOR]

For a donor–acceptor (D–A) molecule, there are three possible cases for its low‐lying excited state (S1): a π–π* state (a localized electronic state), a charge‐transfer (CT) state (a delocalized electronic state), and a mixed or hybridized state of π–π* and CT (named here as the hybridized local and charge transfer (HLCT) state). The HLCT state is an important excited state for the design of next‐generation organic light‐emitting diode (OLED) materials with both high photoluminescence (PL) efficiency and a large fraction of singlet exciton generation in electroluminescence (EL). According to the principle of state mixing in quantum chemistry, a series of twisting D–A molecules are designed and synthesized, and their HLCT state characters are verified by both fluorescent solvatochromic experiments and quantum chemical calculations. The CT components in the HLCT state, which greatly affect the molecular optical properties, are found to be enhanced with a decrease of the twist angle of the D–A segment or an increase of the D–A intensity in these twisting D–A molecules. In OLEDs, using these HLCT compounds as the emitting layer, the maximum exciton utilization efficiency is harvested up to 93%. Surprisingly, an exception of Kasha's rule is revealed in some HLCT compounds: restricted internal‐conversion (IC) from the high‐lying triplet state (T2) to the low‐lying triplet T1, and a reopened path of reverse intersystem crossing (RISC) from T2 to S1 or S2, based on the analysis of the excited‐state energy levels and the measurement of the low‐temperature spectrum. RISC from T2 to S1 (S2) as a “hot exciton” channel is believed to contribute to the large proportion of the radiative singlet excitons. [ABSTRACT FROM AUTHOR]

The reverse intersystem crossing (RISC) process from triplet to singlet manifold can efficiently improve the efficiencies of organic light‐emitting diodes (OLEDs). The relevant RISC rate (kRISC) is one of the key factors that affect the efficiency roll‐off and stability of devices. Here, a new blue "hot exciton" material, CPPCN, with pyrene as the core, is designed and synthesized. Photophysical studies indicate there are multiple high‐lying triplet states near the lowest singlet excited state (S1) of CPPCN, which facilitate the RISC from the high‐lying triplet state (hRISC) to the S1 state. The corresponding hRISC rate constant is determined to be as high as 2.86 × 108 s−1, a value some two to three orders of magnitude higher than typical thermally activated delayed fluorescence materials emitters. Benefiting from this ultrafast hRISC process, non‐doped blue OLED based on CPPCN reaches a high maximum external quantum efficiency (EQE) of 11.64% with suppressed efficiency roll‐off (begin roll‐off at a high brightness of 3732 cd m−2 and retains EQE >8.5% at 10 000 cd m−2). The T95 lifetime of the CPPCN‐based device with a structure of commercial applications is evaluated to be ≈368 h at 1000 cd m−2. [ABSTRACT FROM AUTHOR]

In principle, the ratio (Φ) of the maximum quantum efficiencies for electroluminescence (EL) to photoluminescence (PL) can be expected to approach unity, if the exciton (bound electron-hole pair) generated from the recombination of injected electrons and holes in OLEDs has a sufficiently weak binding energy. However, seldom are examples of Φ > 25% reported in OLEDs because of the strongly bound excitons for most organic semiconductors in nature. Here, a twisting donor-acceptor triphenylamine-thiadiazol molecule (TPA-NZP) exhibits fluorescent emission through a hybridized local and charge-transfer excited state (HLCT), which is demonstrated from both fluorescent solvatochromic experiment and quantum chemical calculations. The HLCT state possesses two combined and compatible characteristics: a large transition moment from a local excited (LE) state and a weakly bound exciton from a charge transfer (CT) state. The former contributes to a high-efficiency radiation of fluorescence, while the latter is responsible for the generation of a high fraction of singlet excitons. Using TPA-NZP as the light-emitting layer in an OLED, high Φ values of 93% (at low brightness) and 50% (at high brightness) are achieved, reflecting sufficient employment of the excitons in the OLED. Characterization of the EL device shows a saturated deep-red emission with CIE coordinates of (0.67, 0.32), accompanied by a rather excellent performance with a maximum luminance of 4574 cd m−2 and a maximum external quantum efficiency (ηext) of ∼2.8%. The HLCT state is a new way to realize high-efficiency of EL devices. [ABSTRACT FROM AUTHOR]

The molecular materials with structures of luminescent core and peripheral carrier groups ( e.g. carbazoles), have exhibited high-performance in organic light-emitting diodes (OLEDs). Present work is to understand the basic process of electronic and energy exchange between the peripheral functional groups and the central core through quantum chemical analysis. As an example, 4,7-bis(9,9-bis(6-(9 H-carbazol-9-yl)hexyl)-9 H-fluoren-2-yl)benzo[ c]-[1,2,5]thiadiazole (TCBzC) is investigated in regards to optoelectronic properties using density functional theory (DFT). The results suggest that the forbidden transition from peripheral carbazole to the central chromophore core makes for separated electrical and optical properties, and high performance electroluminescence (EL) is mainly attributed to the energy-transfer from carbazoles to the fluorene derivative core [ABSTRACT FROM AUTHOR]

Organic conjugated molecules are a category of high solar harvesting material that can convert energy into heat and be utilized as solar‐driven water‐electricity co‐generation. However, the limited absorption range and insufficient photothermal conversion efficiency hinder their application. Herein, two new organic molecules TPA‐BTQ and TPA‐SBTQ, featuring strong electron withdrawing [1,2,5]thiadiazolo[3,4‐g]quinoxaline‐6,7‐dicarboxylate (BTQ) center, terminated by triphenylamine or thiophene‐bridged triphenylamine are designed and synthesized. Detailed theory calculations and spectral analysis confirm that the BTQ unit induces strong intramolecular charge transfer and expands the absorption across a wide spectra range. The flexible alky chain substituted on thiophene inhibits the over‐aggregation and affords more rotation space, leading to suppressed radiative transition and efficient solar‐thermal conversion. Therefore, TPA‐SBTQ powder shows broad absorption across 350 to 1300 nm with a high photothermal conversion efficiency of 18.28% under 1 kW m−2 simulated solar irradiation. Moreover, TPA‐SBTQ is further explored for solar‐thermal conversion applications. The evaporation rate of TPA‐SBTQ solar‐driven water evaporator can reach a remarkable 1.337 kg m−2 h−1 with 92% of water evaporation efficiency under 1 kW m−2 solar irradiation. This study provides guidance for the rational design of high‐efficient organic solar‐thermal materials with a wide absorption spectrum and excellent photothermal conversion efficiency at the molecular level for emerging photothermal‐related applications. [ABSTRACT FROM AUTHOR]

Organic photothermal materials have attracted increasing attention because of their structural diversity, flexibility, and compatibility. However, their energy conversion efficiency is limited owing to the narrow absorption spectrum, strong reflection/transmittance, and insufficient nonradiative decay. In this study, two quinoxaline‐based D–A‐D–A‐D‐type molecules with ethyl (BQE) or carboxylate (BQC) substituents were synthesized. Strong intramolecular charge transfer provided both molecules with a broad absorption range of 350–1000 nm. In addition, the high reorganization energy and weak molecular packing of BQE resulted in efficient nonradiative decay. More importantly, the self‐assembly of BQE leads to a textured surface and enhances the light‐trapping efficiency with significantly reduced light reflection/transmittance. Consequently, BQE achieved an impressive solar‐thermal conversion efficiency of 18.16 % under 1.0 kW m−2 irradiation with good photobleaching resistance. Based on this knowledge, the water evaporation rate of 1.2 kg m−2 h−1 was attained for the BQE‐based interfacial evaporation device with an efficiency of 83 % under 1.0 kW m−2 simulated sunlight. Finally, the synergetic integration of solar‐steam and thermoelectric co‐generation devices based on BQE was realized without significantly sacrificing solar‐steam efficiency. This underscores the practical applications of BQE‐based technology in effectively harnessing photothermal energy. This study provides new insights into the molecular design for enhancing light‐trapping management by molecular self‐assembly, paving the way for photothermal‐driven applications of organic photothermal materials. [ABSTRACT FROM AUTHOR]

Organic photothermal materials have attracted increasing attention because of their structural diversity, flexibility, and compatibility. However, their energy conversion efficiency is limited owing to the narrow absorption spectrum, strong reflection/transmittance, and insufficient nonradiative decay. In this study, two quinoxaline‐based D–A‐D–A‐D‐type molecules with ethyl (BQE) or carboxylate (BQC) substituents were synthesized. Strong intramolecular charge transfer provided both molecules with a broad absorption range of 350–1000 nm. In addition, the high reorganization energy and weak molecular packing of BQE resulted in efficient nonradiative decay. More importantly, the self‐assembly of BQE leads to a textured surface and enhances the light‐trapping efficiency with significantly reduced light reflection/transmittance. Consequently, BQE achieved an impressive solar‐thermal conversion efficiency of 18.16 % under 1.0 kW m−2 irradiation with good photobleaching resistance. Based on this knowledge, the water evaporation rate of 1.2 kg m−2 h−1 was attained for the BQE‐based interfacial evaporation device with an efficiency of 83 % under 1.0 kW m−2 simulated sunlight. Finally, the synergetic integration of solar‐steam and thermoelectric co‐generation devices based on BQE was realized without significantly sacrificing solar‐steam efficiency. This underscores the practical applications of BQE‐based technology in effectively harnessing photothermal energy. This study provides new insights into the molecular design for enhancing light‐trapping management by molecular self‐assembly, paving the way for photothermal‐driven applications of organic photothermal materials. [ABSTRACT FROM AUTHOR]

In this contribution, a unique donor‐acceptor conjugated organic‐small‐molecule photothermal material, namely GDPA‐QCN, is presented. Bulky dendritic triphenylamine (GDPA) was grafted onto quinoxaline‐6,7‐dicarbonitrile (QCN) with a phenyl ring as a bridge to form an "umbrella" architecture. Benefited from the particular molecular structure, in solid state, GDPA‐QCN molecules adopted a loose packing mode due to the steric effect of "umbrella head" dendritic triphenylamine and flexible molecular structure feature, which allows efficient intramolecular motions and consequently elevates energy dissipation by taking the pathway of thermal deactivation within broad absorption range. The GDPA‐QCN solid has high solar‐thermal conversion efficiency with an absorption range from 300 to 1100 nm, which can promote superior water purification and electricity generation performance. [ABSTRACT FROM AUTHOR]

In this contribution, a unique donor‐acceptor conjugated organic‐small‐molecule photothermal material, namely GDPA‐QCN, is presented. Bulky dendritic triphenylamine (GDPA) was grafted onto quinoxaline‐6,7‐dicarbonitrile (QCN) with a phenyl ring as a bridge to form an "umbrella" architecture. Benefited from the particular molecular structure, in solid state, GDPA‐QCN molecules adopted a loose packing mode due to the steric effect of "umbrella head" dendritic triphenylamine and flexible molecular structure feature, which allows efficient intramolecular motions and consequently elevates energy dissipation by taking the pathway of thermal deactivation within broad absorption range. The GDPA‐QCN solid has high solar‐thermal conversion efficiency with an absorption range from 300 to 1100 nm, which can promote superior water purification and electricity generation performance. [ABSTRACT FROM AUTHOR]

In contrast to the common intramolecular charge transfer (ICT) emission, planarized intramolecular charge transfer (PLICT) based materials usually possess higher proportion radiative decay for their flat and rigid conformation in excited states. Herein, a strategy for designing PLICT‐based emitters by the excited state quinone‐conformation induced planarization is proposed. By virtue of RIR mechanism on TPP (tetraphenylpyrazinyl) unit, the newcomers named as TPP‐PPI (1‐phenyl‐2‐(4′‐(3,5,6‐triphenylpyrazin‐2‐yl)‐[1,1′‐biphenyl]‐4‐yl)‐1H‐phenanthro[9,10‐d] imidazole) and TPP‐PI (1‐phenyl‐2‐(4‐(3,5,6‐triphenylpyrazin‐2‐yl)phenyl)‐1H‐phenanthro[9,10‐d]imidazole) exhibit aggregation‐induced emission (AIE) characteristics. TPP‐PPI and TPP‐PI have obvious PLICT properties via series of spectral measurements. Employing theoretical calculation in ground and excited states in different solvents, their PLICT process is confirmed further, and TPP's contribution on PLICT formation becomes clear. In non‐doped organic light‐emitting diodes, these two emitters with AIE and PLICT characteristic exhibit good performance with external quantum efficiency (4.85% and 4.36%) as blue emitters. [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]

Recently, organic–inorganic metal halide perovskite solar cells (PSCs) have achieved rapid improvement, however, the efficiencies are still behind the Shockley–Queisser theory mainly due to their high energy loss (ELOSS) in open‐circuit voltage (VOC). Due to the polycrystalline nature of the solution‐prepared perovskite films, defects at the grain boundaries as the non‐radiative recombination centers greatly affect the VOC and limit the device efficiency. Herein, poly(vinylidene fluoride) (PVDF) is introduced as polymer‐templates in the perovskite film, where the fluorine atoms in the PVDF network can form strong hydrogen‐bonds with organic cations and coordinate bonds with Pb2+. The strong interaction between PVDF and perovksite enables slow crystal growth and efficient defect passivation, which effectively reduce non‐radiation recombination and minimize ELOSS of VOC. PVDF‐based PSCs achieve a champion efficiency of 24.21% with a excellent voltage of 1.22 V, which is one of the highest VOC values reported for FAMAPb(I/Br)3‐based PSCs. Furthermore, the strong hydrophobic fluorine atoms in PVDF endow the device with excellent humidity stability, the unencapsulated solar cell maintain the initial efficiency of >90% for 2500 h under air ambient of ≈50% humid and a consistently high VOC of 1.20 V. [ABSTRACT FROM AUTHOR]

Acceptor-substituted polycarbazoles (PCzTPAN) and polytriphenylamines (PTPATPAN) bearing electron-deficient 2,3,3-triphenylacrylonitrile (TPAN) side groups have been successfully synthesized. Both of them are aggregation-induced emission (AIE)-active and show intramolecular charge transfer (ICT) behavior. PCzTPAN and PTPATPAN aggregates in 90% water/THF were used for the detection of 1,3,5-trinitrobenzene (TNB) as prototypical nitroaromatic compound. They show amplified PL quenching upon addition of TNB with a maximum quenching constant of 5.5 × 10 5 M −1 . As additional application example, the detection of the glass transition temperature of polystyrene (PS) was accomplished for PTPATPAN blended into PS at doping concentrations of 0.1–1.0 wt%. [ABSTRACT FROM AUTHOR]

Organic luminophores of narrowband emission are considered a filter-less light resource, promising for high-resolution organic light-emitting diode (OLED) display technology. It is essentially feasible to achieve narrowband emission by manipulating the intrinsic structural relaxation and vibronic coupling in the excited state. On this basis, by the introduction of single bond-linked peripheral moieties of 4-methoxyphenyl into the benzo[c]benzo [7,8]quinolino[1,2,3-fg]acridine-7,11-dione (BAO) core, the resulting BAO-PMO is observed to exhibit better performance, achieving a full width at half-maximum (FWHM) of down to 27 nm/0.14 eV in toluene for the narrowest band compared with that of BAO (35 nm/0.20 eV). An effective strategy is thus proposed by the significant enhancement of the low-frequency vibronic coupling strength with simultaneous mitigation of the high-frequency ones to realize the control of structural relaxation. In consequence, the BAO-PMO based OLED device exhibits a narrowband green emission with an FWHM of 37 nm/0.18 eV. • Organic narrowband luminophores based on carbonyl-bridged triarylamine were shown. • The emission narrowing was achieved via vibronic coupling regulation of the excited-state configuration. • Doped OLEDs exhibit narrowband green emission with a full width at half-maximum of down to 37 nm. [ABSTRACT FROM AUTHOR]

In this contribution, a unique donor‐acceptor conjugated organic‐small‐molecule photothermal material, namely GDPA‐QCN, is presented. Bulky dendritic triphenylamine (GDPA) was grafted onto quinoxaline‐6,7‐dicarbonitrile (QCN) with a phenyl ring as a bridge to form an “umbrella” architecture. Benefited from the particular molecular structure, in solid state, GDPA‐QCN molecules adopted a loose packing mode due to the steric effect of “umbrella head” dendritic triphenylamine and flexible molecular structure feature, which allows efficient intramolecular motions and consequently elevates energy dissipation by taking the pathway of thermal deactivation within broad absorption range. The GDPA‐QCN solid has high solar‐thermal conversion efficiency with an absorption range from 300 to 1100 nm, which can promote superior water purification and electricity generation performance. [ABSTRACT FROM AUTHOR]

Organic fluorescent emitters with narrowband emissions are highly desirable for high‐resolution organic light‐emitting diode (OLED) display technology. In principle, this can be achieved by specifically controlling the intrinsic structural relaxation and vibronic coupling in the excited state. Here, a design strategy to realize narrowband emission of organic fluorescent emitters is proposed by significantly enhancing the low‐frequency vibronic coupling strength (Λ) while simultaneously reducing the high‐frequency Λ of the commonly involved stretching modes. The quinolino‐[3,2,1‐de]acridine‐5,9‐dione (QAO) species is found to be directly associated with this design principle. By introducing single bond‐linked peripheral moieties into the QAO core, the constructed QAO derivatives are shown to exhibit better performance, by achieving a full width at half‐maximum of 23 nm/0.13 eV in toluene for the narrowest band as well as 27 nm/0.15 eV in doped devices, with negligible dependence on the doping concentrations. The maximum external quantum efficiency of the fabricated blue OLED is 17.5%. [ABSTRACT FROM AUTHOR]

[Display omitted] • The inhibition of the vibration of the molecules in the aggregated state is the main reason for its AIE mechanism. • It was found that the introduction of cyanine into the acceptor part of the molecule would make △ESTsmaller. • The cyano connections between the acceptor and other acceptors can effectively increase the twist angle and promote the reverse inter-system crossing process. Wise design strategies for efficient thermally activated delayed fluorescence (TADF) molecules are highly desirable. In this work, the effect of cyano-substitution effects on the molecular photophysical properties of five TADF molecules was investigated. The energy gap (△E ST), natural transition orbitals (NTOs) properties, the Huang-Rhys factor and reorganization energies, rate constants for the intersystem crossing (k ISC) and reverse intersystem crossing (k RISC) are analyzed based on density functional theory (DFT) and time-dependent density functional theory (TD-DFT) in combination with the thermal vibration correlation function (TVCF) method to measure method. CzTrzBp-CN-4 has the smallest △E ST and larger spin-orbital coupling (SOC) in the film, leading to larger k RISC , suggesting that the cyano connections between the acceptor and other acceptors can effectively increase the twist angle and promote the k RISC , predicting that it may have TADF properties. [ABSTRACT FROM AUTHOR]

In this study, we have theoretically investigated the solid-state effects of three molecules that combine the hot exciton and AIE mechanisms. The results show that the AIE effect is verified by the decreased H-R factor of the molecule in the solid phase due to the RIR effect.TPAPHOC2 has stronger intermolecular interactions in the solid phase and its fluorescence quantum yield is more different from that in solution. The molecules have smaller ΔES1-T2 and larger SOC in thin films, which promotes the RISC process. The study well explains the experimental results and provides insights into the molecular design. [Display omitted] • The inhibition of the vibration of the studied molecules in the aggregated state is the main reason for its AIE mechanism. • The molecules exhibit a smaller △ES1-T1 and a more significant SOC in aggregate state, which is more favorable for the RISC. • Distinct interactions between solid-state molecules lead to significant differences solid-state luminescence efficiency. In this study, we have theoretically investigated the solid-state effects of three molecules that combine the hot exciton and AIE mechanisms. The results show that the AIE effect is verified by the decreased H-R factor of the molecule in the solid phase due to the RIR effect.TPAPHOC2 has stronger intermolecular interactions in the solid phase and its fluorescence quantum yield is more different from that in solution. The molecules have smaller ΔE S1-T2 and larger SOC in thin films, which promotes the RISC process. The study well explains the experimental results and provides insights into the molecular design. [ABSTRACT FROM AUTHOR]

Fluorescent emitters with both high exciton utilization and luminescence efficiency show promising applications in organic light-emitting diodes (OLEDs), especially those with simultaneously aggregation-induced emission (AIE) and thermally activated delayed fluorescence (TADF). In this work, we performed multi-scale simulations to investigate the photophysical properties of the reported red AIDF compounds T-DA-1, C-DA-1, T-DA-2 and C-DA-2, molecules with the same donor-acceptor group but with very different emission wavelengths and photoluminescence quantum yields (Φ PL) due to different connection points. The packing modes of molecules in film are obtained by molecular dynamics (MD) simulations, the crystal structure is given from the experiment, and then the photophysical properties with the consideration of the solid-state effect are studied by using the combined quantum mechanics and molecular mechanics (QM/MM) method. Natural transition orbitals (NTOs), adiabatic singlet-triplet state energy levels, reorganization energies and HR factors are analysed in detail. In addition, radiative and non-radiative transitions as well as inter-system crossing (ISC) and reverse inter-system crossing (RISC) processes are also investigated. Our results indicate that there is an important role of different substitution positions on the photo physical properties of TADF molecules. The trans- arrangement substitutions restrict the geometry variations, hinder the non-radiative energy consumption process, and promote the radiative process of TADF molecules. In addition, the trans- arrangement in the aggregated state has a smaller ΔE ST and a larger SOC, which could favorite the RISC process. Last, the films and crystals of the trans- arrangement molecules have stronger π-π stacking, it limit the movement of molecules, which may inhibit the nonradiative deactivation caused by intramolecular torsional and vibrational excited-energy loss. Our work reasonably elucidates the experimental results and highlights the effect of different substitution positions on TADF properties. This could provide a theoretical perspective for designing efficient AIDF molecules. [Display omitted] • Substitution effects with trans/ cis -arrangement on excited-state properties are studied. • Photo-physical properties of total 4 molecules are theoretically studied by DFT, TD-DFT and TVCF methods. • RelAtionships between trans/ cis -arrangement structures and luminescent properties are revealed. • Trans -arrangement molecules with stronger π-π stacking induce smaller △E ST and large SOC in aggregate state. [ABSTRACT FROM AUTHOR]

In this work, we report two isomers composed of 1-phenyl-1 H -phenanthro[9,10 -d ]imidazole (PI), hydroxyl and tetraphenylethylene (TPE), abbreviated as m -PITPE and p -PITPE. It is found that they exhibit similar aggregation-induced emission (AIE) behavior but totally different excited-state intramolecular proton transfer (ESIPT) characteristic, as a result of the different linkage sites of PI on TPE moiety. Theoretical calculations and their different experimental responses to F− demonstrate that only the para -linkage isomer displays ESIPT. In m -PITPE with meta -linkage, the electron cloud distribution only locates at the TPE part in the singlet excited (S 1) states, which results in the localized excited state without ESIPT characteristic. Image 1 [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]

[Display omitted] • The luminescence mechanisms of TADF-AIE molecules DMAC-TRZ, PFDMACTRZ and DPFDMAC-TRZ were investigated using QM/MM and MD. • Different aggregation models induce different intermolecular interactions and molecular geometries. • The AIE property was confirmed by the luminescence properties in aggregation states, where its enhanced k r and reduced k nr. • The molecular aggregation state reduces the ΔE S1-T1 , and enhances the SOC, thus increasing the k (R)ISC. Multifunctional TADF molecules have attracted significant attention from the field. In this work the luminescence mechanisms of TADF-AIE molecules DMAC-TRZ, PFDMAC-TRZ and DPFDMAC-TRZ in distinct aggregation states were investigated using QM/MM method and MD simulations. Results show that the AIE property was confirmed by comparing the luminescence properties in different aggregation states, where the molecule aggregates with its enhanced radiation rate and reduced non-radiation rate. In addition, the aggregation state reduces the ΔE S1-T1 , and enhances the SOC, thus increasing the k (R)ISC. The computational results provide valuable information for understanding the luminescence mechanism of molecules with TADF-AIE properties. [ABSTRACT FROM AUTHOR]

In this work, a novel green emitter, namely 16,16-dimethylbenzo[ a ]quinolino[3,2,1- de ]acridin-10(16 H)-one (GACQ), with amine‒carbonyl fused structure has been designed and synthesized. The single-crystal structure analysis confirmed that the fused structure shows non-planar conformation with dihedral angle of 48.97° from the front-view direction. The photophysical and theoretical results confirmed that GACQ exhibited hybridized local and charge-transfer (HLCT) feature with strong green emissions of 513 and 535 nm in solution and film, respectively. The non-doped device based on GACQ achieved high luminance (15810 cd m−2) and good efficiency stability with negligible external quantum efficiency (EQE) roll-off. Furthermore, the doped device exhibited high maximum EQE of 4.8% with CIE coordinate of (0.38, 0.58). [Display omitted] • A novel amine‒carbonyl fused emitter, GACQ, has been successfully constructed. • GACQ possesses hybridized local and charge-transfer characteristic. • Non-doped device of GACQ exhibited high luminance and negligible EQE roll-off. • Doped device based on GACQ achieved maximum EQE of up to 4.8%. [ABSTRACT FROM AUTHOR]

We have designed and synthesized a novel asymmetric amine‒carbonyl fused emitter, BACQ, having a hybridized local and charge-transfer emissive state. From the single-crystal analysis, the BACQ exhibited non-planar configuration with multiple C–H‧‧‧O and C–H‧‧‧π interactions, which could rigidify the molecule and provide good thermal stability. Non-doped device based on BACQ present sky-blue emission with maximum luminance of 11180 cd m−2, and external quantum efficiency of 2.48% with small roll-off. • A novel asymmetric amine‒carbonyl fused emitter, BACQ, has been synthesized. • BACQ has hybridized local and charge-transfer feature. • Non-doped device of BACQ exhibited high luminance of 11180 cd m−2. • Non-doped device of BACQ achieved maximum EQE of 2.48% with small roll-off. [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]

The performance of organic deep-blue emitters is still unsatisfactory, and the effective design strategy is needed for efficient organic electroluminescent materials. In this work, a novel fused chromophore moiety, 5,5,9,9-tetramethyl-5,9-dihydrobenzo[ a ]quinolino[1,2,3-fg] acridine (TMBQA), has been successfully constructed. Based on TMBQA as an electron donor and fluorine (-F) or cyano (-CN) as acceptors, BF and BCN have been synthesized and they exhibited the desired deep-blue emission both in solvents and neat films. The non-doped devices based on them show narrow band deep-blue emission with CIE coordinates nearly approach NTSC standard. In particular, the BCN-based device has a maximum external quantum efficiency of 5.6% with CIE coordinate of (0.15, 0.08). [Display omitted] • A novel fused chromophore moiety, TMBQA, has been successfully constructed. • Based on TMBQA, two deep-blue emitters (BF and BCN) have been designed and synthesized. • Non-doped devices exhibited efficient deep-blue emission with narrow FWHM. • BCN-based device achieved maximum external quantum efficiency of up to 5.6%. [ABSTRACT FROM AUTHOR]

Excited state characters and components play a decisive role in photoluminescence (PL) and electroluminescence (EL) properties of organic light-emitting materials (OLEDS). Charge-transfer (CT) state is beneficial to enhance the singlet exciton utilizations in fluorescent OLEDs by an activated reverse intersystem crossing process, due to the minimized singlet and triplet energy splitting in CT excitons. However, the dominant CT component in the emissive state significantly reduces the PL efficiency in such materials. Here, the strategy is to carry out a fine excited state modulation, aiming to reach a golden combination of the high PL efficiency locally emissive (LE) component and the high exciton utilizing CT component in one excited state. As a result, a quasi-equivalent hybridization of LE and CT components is obtained in the emissive state upon the addition of only an extra phenyl ring in the newly synthesized material 4-[2-(4′-diphenylamino-biphenyl-4-yl)-phenanthro[9,10-d]imidazol-1-yl]-benzonitrile (TBPMCN), and the nondoped OLED of TBPMCN exhibited a record-setting performance: a pure blue emission with a Commission Internationale de L'Eclairage coordinate of (0.16, 0.16), a high external quantum efficiency of 7.8%, and a high yield of singlet exciton of 97% without delayed fluorescence phenomenon. The excited state modulation could be a practical way to design low-cost, high-efficiency fluorescent OLED materials. [ABSTRACT FROM AUTHOR]

A series of highly efficient deep blue emitters comprising of carbazole and phenanthro[9,10-d]imidazole moieties are designed and synthesized. These compounds present deep blue emission, narrow FWHM, high quantum yields, high thermal and morphological stabilities. Among them, the design strategy of 2:1 ratio of phenanthro[9,10-d]imidazole and carbazole unit affords M2 with more balanced carrier injection and transporting properties. OLEDs using M2 as emitting layer is observed to deliver a truly deep blue CIE of y < 0.06 with a highest external quantum efficiency of 3.02%. By taking the full advantage of these deep blue emitters, they are further served as excellent hosts for fluorescent and phosphorescent dyes. High-performance green phosphorescent device based on M2/Ir(ppy) 3 is attained with a maximum current efficiency of 33.35 cd A −1 , a power efficiency of 22.99 lm W −1 and a maximum external quantum efficiency of 9.47%. When doped with an orange fluorescent material, upon careful tuning the doping proportion, the two-emitting-component white OLED is successfully fabricated with a maximum current efficiency of 5.53 cd A −1 and CIE coordinates of (0.313, 0.305). Both the non-doped and doped devices exhibited high operational stability with negligible efficiency roll-off over the broad current density range. [ABSTRACT FROM AUTHOR]

The design concept of separation of optical and electrical bandgap for wide bandgap materials is further developed in DCzSiPI. The HOMO/LUMO levels can be tuned by incorporation of PI and DCz substituents. The tetraphenylsilane core avoids the intramolecular charge transfer from DCz to PI (DCz=dimer carbazole, PI=phenanthro[9,10- d]imidazole). The allowed transitions are found to be from HOMO−1 to LUMO providing DCzSiPI with sufficient bandgap. [ABSTRACT FROM AUTHOR]

Highlights: [•] Electropolymerized (EP) films are introduced to detect TNT. [•] EP films have displayed the high sensitivity to TNT in vapor and aqueous medium. [•] EP films have displayed sensitivity to TNT in natural water. [•] TCPC EP film is demonstrated a superior TNT sensor by theoretical calculation. [Copyright &y& Elsevier]

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]

A novel 3-5-dichlorosalicylaldehyde Schiff base chemodosimeter (compound 1) for water is designed and synthesized, and it works based on a water-triggered reaction of a Schiff base. Addition of trace amounts of water into 1 in various organic solvents leads to a fluorescence turn-on response and a simultaneous dual-channel signal modulation (both in the fluorescence and absorption spectra). Especially, 1 is found to be an outstanding fluorescence enhancement water sensor in methanol with an extremely low detection limit of 22 ppm. Consequently this probe can be utilized to detect trace water in commercial methanol. The quantitative detection of a wide range of water content is enhanced in THF and acetonitrile (0–35% v/v for THF and 0–20% v/v for acetonitrile), where the fluorescence peak intensity is nearly proportional to the amount of water added. Moreover, 1 can be used for monitoring pH through a novel ON–OFF–ON type signal modulation both in fluorescence and absorption spectra within a wide pH detection range. Thus, the chemodosimeter can not only be utilized to monitor the intracellular pH fluctuations, but also to accomplish simultaneous in situ staining of the cytosol and acidic organelles in two different channels, respectively. [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]

A greatly enhanced proportion of radiative excitons in non-doped blue electroluminescence with a maximum exciton utilizing efficiency (EUE) of 85% is harvested in the orthogonal cyano substituted, charge transfer (CT) emitter TPMCN, in comparison to the localized emission (LE)-like emitter TPM with a low EUE of 16%. [ABSTRACT FROM AUTHOR]