Developing ultra-deep-blue (UDB) OLED emitters with both low CIEy value and reasonable device efficiency remains challenging because wide-bandgap materials usually suffer from difficult charge injection, aggregation-caused quenching, and emission red shifts caused by excessive intramolecular charge transfer (ICT). Herein, we report a weak-ICT molecular design strategy by combining a highly rigid locked phenocarbazole (LPCz) donor with a moderately electron-withdrawing 1,3,4-oxadiazole (OXD) acceptor. Two D-A-type emitters, LPCz-tBuOXD and LPCz-MeOOXD, were designed and synthesized by introducing tert-butyl and methoxy terminal substituents, respectively, to regulate steric hindrance and intermolecular interactions. The rigid LPCz framework suppresses excited-state structural relaxation, while the weak OXD acceptor helps maintain high-energy emissive states and improves electron-transport characteristics without inducing excessive ICT. Both the emitters exhibited weak-ICT/LE-dominated excited-state features, large singlet-triplet energy gaps, nanosecond-scale fluorescence lifetimes, and excellent thermal stability with decomposition temperatures above 410 °C. Single-crystal analysis of LPCz-tBuOXD further revealed a loose molecular packing mode without close face-to-face π‒π stacking, supporting the role of the bulky tert-butyl group in suppressing detrimental intermolecular aggregation. The doped OLEDs based on these emitters achieved UDB electroluminescence with emission peaks at 424 – 428 nm and low CIEy values of 0.044 – 0.049. Notably, the optimized LPCz-tBuOXD-based device with 10 wt% doping concentration exhibited a maximum external quantum efficiency of 7.15% with CIE coordinates of (0.152, 0.046), outperforming the corresponding LPCz-MeOOXD-based device. These results demonstrate that integrating a rigid LPCz donor, a weak OXD acceptor, and terminal steric modulation is an effective strategy for constructing low-CIEy UDB fluorescent OLED emitters.

Despite their potential for organic light-emitting diodes (OLEDs), the performances of conventional thermally activated delayed fluorescence (TADF) emitters are often limited by aggregation-caused quenching (ACQ), thus usually requiring dispersion into a host matrix to suppress luminescence quenching and exciton annihilation. The emergence of aggregation-induced emission (AIE) technology has enabled the development of AIE-TADF materials capable of overcoming ACQ to exhibit excellent luminescent efficiency. In this work, a series of acridine-dicyanopyridine/1,3,5-triazine derivatives featuring AIE-TADF properties (TPADPAC-MPC, TPADPAC-TRZ, DPAC-TFPC, TFDPAC-MPC) were designed and synthesized through the strategic modification of 9,9-diphenylacridine (DPAC) core with triphenylamine (TPA) and 4-trifluoromethylphenyl group, followed by combination with diverse electron-accepting units, that is, 2,4,6-triphenyl-1,3,5-triazine (TRZ), 3,5-dicarboni-trile (MPC) and 2,6-bis(4-(trifluoromethyl)phenyl)pyridine-3,5-dicarbonitrile (TFPC). The resulting compounds exhibited simultaneously AIE and TADF properties. The influence of donor/acceptor substituents on the molecular AIE-TADF properties was investigated by using crystallography, theoretical calculations and spectral analyses. Non-doped OLEDs fabricated from these emitters revealed that the device employing TPADPAC-TRZ possessed distinct advantages in terms of the turn-on voltage (3.6 V), the maximum luminance (5589 cd/m2), and power efficiency (13.92 lm/W), whereas the device based on DPAC-TFPC displayed the optimal current efficiency (19.64 cd/A) and external quantum efficiency (8.91%).

Two Y-shaped imidazole-derived chromophores, DMAC-1t-IM-(1t-TPA)2 and DPAC-1t-IM-(1t-TPA)2, with imidazole unit as the acceptor and two triphenylamine (TPA) moieties attached at C4 and C5 positions of imidazole ring and one 9,9-dimethylacridine (DMAC) or 9,9-diphenylacridine (DPAC) moiety attached at C2 position of imidazole ring, were designed and synthesized for solution-processed blue OLEDs. Both of the compounds displayed deep-blue emission in toluene solution with photoluminescent quantum yield (PLQY) of 63.26 % for DMAC-1t-IM-(1t-TPA)2 and 65.61 % for DPAC-1t-IM-(1t-TPA)2, while they exhibited green emission in thin films with PLQY of 30.33 % and 24.48 %, and the compounds showed excellent thermal stability with the decomposition temperatures of 457 degrees C and 491 degrees C, respectively. In the absence of the hole-transporting layer, the solution-processed doped devices using the blend of 1,3-di(9H-carbazol-9-yl)benzene (mCP) with the Y-shaped imidazole-derived chromophores as emitting layers emitted deep-blue emission a maximum luminance (Lmax) of 1206 cd/m2 and a maximum external quantum efficiency (EQEmax) of 2.40 % for DMAC-1t-IM-(1t-TPA)2 and a Lmax of 944 cd/m2 and a EQEmax of 3.60 % for DPAC-1t-IM-(1t-TPA)2, respectively, suggesting that these compounds have a great potential as the organic emitters for deep-blue OLEDs.

To achieve a synergistic enhancement of ultra-high exciton utilization and high radiative transition rates, herein, using 6H-indolo[2,3-b]quinoxaline as the building block, two traditional TADF materials (MeOTPAIQCN-1 and MeOTPAIQCN-2) and two hot exciton materials (DPCzIQCN and TPAIQCN) were successfully synthesized by employing a molecular design strategy based on "regional functionalization". By regulating the donor to match the S-1 state with the T-n state, efficient utilization of triplet excitons can be achieved. The frontier molecular orbitals, hole-electron interactions, photophysical properties, electrochemical properties, thermal stabilities and organic electroluminescent performances of these compounds were investigated through theoretical calculations and experimentations. These four compounds exhibited emissions ranging from green to near-infrared light in solid films, and the compound TPAIQCN showed green emission with the fluorescence quantum yield approaching 100% in toluene solution. They also demonstrated excellent thermal stability (T-d > 450 degrees C). Using 3,3 '-di(9H-carbazol-9-yl)-1,1 '-biphenyl (mCBP) as the host material, the four compounds were used as the dopants to fabricate the organic electroluminescence devices via thermal evaporation. The doped device based on TPAIQCN showed green emission with the maximum external quantum efficiency (EQE(max)) of 5.70% and the maximum luminance (L-max) of 12780 cd/m(2) at the doping concentration of 10 wt%, while the MeOTPAIQCN-2 device exhibited yellow emission with the EQE(max) of 8.81% and the L-max of 5930 cd/m(2) at the doping concentration of 10 wt%.

Four novel heterocyclic compounds based on spiro[fluorene-9,9 '-xanthene] (SFX), 2MeCNPy-Ph-SFX, 2MeCNPy-2MePh-SFX, 2PyCNPy-Ph-SFX and PyCNPm-Ph-SFX, have been synthesized by attaching the different dicyano-substituted pyridine acceptors and monocyano-substituted pyrimidine acceptor to the xanthene moiety of the SFX donor, respectively. The photophysical and electrochemical properties and thermal stabilities of these compounds were investigated systematically. These compounds exhibit good thermal stability, and display intense deep-blue emission in solution. Using 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi) as the electron-transporting material, the thermal deposited devices with 2MeCNPy-Ph-SFX or PyCNPm-Ph-SFX in CBP host as the emissive layers were fabricated to investigate their electroluminescence performances, the devices of 2MeCNPy-Ph-SFX exhibited deep-blue emission with a maximum luminance (Lmax) of 1282 cd/m2, a maximum current efficiency (CEmax) of 1.36 cd/A and a maximum external quantum efficiency (EQEmax) of 1.98 %, while the devices of PyCNPm-Ph-SFX displayed blue emission with with the Lmax of 1476 cd/m2, the CEmax of 1.84 cd/A and the EQEmax of 1.49 %.

Two novel host materials, Spy and Apy, were successfully synthesized by a C-N coupling reaction between a 3,6-di-tert-butylcarbazole donor unit and a cyanopyridine acceptor group. Their photophysical and electrochemical properties, thermal stability, and electroluminescent properties were systematically investigated following comprehensive structural characterization. Solution-processed OLED devices with the configuration ITO/PEDOT:PSS (40 nm)/host:4CzIPN (30 nm)/TmPyPb (35 nm)/Liq (2 nm)/Al (200 nm) were fabricated, in which 4CzIPN was incorporated as a dopant in both the Spy and Apy host matrices. Both devices exhibited electroluminescence peaks centered at approximately 510 nm, consisting with the maximum fluorescence emission wavelength of 4CzIPN, which indicates the potential efficient Fo & uml;rster energy transfer from the host to the guest. The device based on the Spy host demonstrated superior performance, with a turn-on voltage of 4.4 V, maximum luminance of 1392 cd/m2, maximum current efficiency of 17.11 cd/A, maximum power efficiency of 9.61 lm/W, and a maximum external quantum efficiency of 5.82%. These results highlight the remarkable potential of Spy as an efficient host material for solution-processed OLED applications.

Julolidinyl group can facilitate the overlap of the p-orbital of the nitrogen atom with its adjacent phenyl ring, and thus can improve the strength of electron-donating groups for enhancing optoelectronic properties of the materials. In this work, two new tetramethyljulolidine-fused biscoumarins, JCC-Cz and JCC-2Cz, were synthesized as the organic emitters for organic light-emitting diodes. Their photophysical and electrochemical properties and thermal stability were investigated systematically. The tetramethyljulolidine-fused biscoumarins exhibited significant bathochromic shift of both absorption and emission maxima in solution and thin films and were accompanied by increase in the fluorescence quantum yields in comparison with the diethylamine-substituted biscoumarin analogues. Using different host materials, the doped devices based on JCC-Cz and JCC-2Cz as the emitting materials were fabricated by solution-processing the emitting layers to investigated their electroluminescence (EL) performances. In the doped devices using a blend of PVK:PBD as the mixed host material, the devices of JCC-Cz and JCC-2Cz exhibited orange emission with a maximum external quantum efficiency (EQEmax) of 2.08 % for JCC-Cz and 2.43 % for JCC-2Cz. In the doped devices using mCP as the host material, the device of JCC-Cz with the doping concentration of 5 wt% showed near white emission with a maximum luminance (Lmax) of 501 cd/m2 and a maximum external quantum efficiency (EQEmax) of 2.24 % and CIE of (0.35, 0.38).

Two 6,7-dicyanoquinoxaline/carbazole hybrid compounds (DCNQx-1 and DCNQx-2) were synthesized by introducing different carbazole groups into the quinoxaline-6,7-dicarbonitrile skeleton through the phenyl-bridged linkers, and characterized by NMR (1H and 13C) and high resolution mass spectrometry. The structure-property relationship of the compounds was revealed by exploring their thermal stability, photophysical and electrochemical properties. The compounds DCNQx-1 and DCNQx-2 showed bright orange red and green emission with the fluorescence quantum yield of 5.86% for DCNQx-1 and 64.87 % for DCNQx-2 in toluene solution, and exhibited red and yellow emission with the fluorescence quantum yield of 19.50% and 23.52% in solid states, respectively. Using tris(4-carbazoyl-9-ylphenyl)amine (TCTA) as the host material and 1,3-bis[3,5-di(pyridin-3-yl)phenyl]benzene (BmPyPB) as the electron transport material, the host-containing devices with a configuration of ITO/PEDOT:PSS (40 nm)/TCTA:DCNQx-derivative (x wt%) (30 nm)/BmPyPB (35 nm)/Liq (2 nm)/Al (200 nm) were fabricated by solution-processing the emitting layers to investigated their electroluminescence (EL) performances. In the absence of the hole-transporting layers, the host-containing devices of DCNQx-1 showed the maximum luminance (Lmax) was 3766 cd/m2, the maximum current efficiency (CEmax) was 15.55 cd/A, and the maximum external quantum efficiency (EQEmax) was 6.89%. The host-containing devices of DCNQx-2 exhibited the best EL performances with Lmax of 3786 cd/m2, CEmax of 28.45 cd/A and EQEmax of 8.85%.

The unique molecular structure of fused-biscoumarins endows them with intriguing photophysical properties, making some of them excellent fluorophores. However, their poor solubility limits their application in the solution-processable organic light-emitting diodes (OLEDs). In this work, to improve the solubility of the fused-biscoumarins for the solution-processable OLEDs, two new V-shaped fused-biscoumarins containing tert-butyl group modified imidazole/carbazole groups, VBC-IM and VBC-BuCz, were successfully synthesized and characterized. Both compounds exhibit intense green emission in dichloromethane solution and good thermal stability. In the absence of the hole-transporting layers, the doped devices using the solution-processed emitting layers of CBP:VBC-IM or VBC-BuCz emit green emission with the maximum external quantum efficiency (EQEmax) of 1.63% and 1.82%, and the maximum luminance (Lmax) of 2059 cd/m2 and 2796 cd/m2, respectively.

Two spiroindoloacridine-fluorene (SIAF)/oxadiazole hybrids (SIAF-tBuOXD and SIAF-MeOOXD) have been synthesized by the Suzuki cross-coupling reactions between the spiroindoloacridine-fluorene boronic ester and 2-(4-bromophenyl)-5-(4-(tert-butyl)phenyl)-1,3,4-oxadiazole (tBuOXD) and 2-(4-bromophenyl)-5-(4-methoxyphenyl)-1,3,4-oxadiazole (MeOOXD), respectively. Their photophysical and electrochemical properties and thermal stabilities, as well as organic electroluminescent performances were investigated through theoretical calculations and experimental measurements. These compounds displayed excellent thermal stability (T-d > 350 degrees C), and exhibited intense deep-blue emission (ca. 399 nm) with a full width at half maximum (FWHM) of 48 nm and high fluorescence quantum yield approaching 100 % in toluene solution. By using 1,3-bis(N-carbazolyl)benzene (mCP) as the host material and solution-processing the emitting layers, the doped devices without the hole-transporting layers exhibited deep-blue emissions with a maximum external quantum efficiencies (EQE(max)) of 5.01 % for SIAF-tBuOXD and 4.76 % for SIAF-MeOOXD.

Two new 3,8,13-trisubstituted triazatruxene derivatives containing different imidazole-derived moieties, 3,8,13-TPI-TAT and 3,8,13-TTPI-TAT, were successfully synthesized by grafting different imidazole-derived moieties (phenanthroimidazole (PI) and 1,4,5-triphenylimidazole (TPI)) onto the 3,8,13-positions of a triazatruxene (TAT) core, and characterized by NMR (1H and 13C), high resolution mass spectrometry. Using the already reported 3,8,13-TBI-TAT as a comparison, the thermal stability, photophysical and electrochemical properties of these compounds were comparatively investigated to reveal the effects of different imidazole-derived groups on the luminescence properties of the compounds. The doped devices with a structure of ITO/PEDOT:PSS (45 nm)/PVK:PBD (7:3, wt%):TAT compounds (x wt%) (30 nm)/TPBi (20 nm)/Liq (2 nm)/Al (150 nm) and non-doped devices were fabricated by solution-processed the emitting layers to investigate their electroluminescence (EL) performances, in which the devices of the diphenylimidazole substituted compound (3,8,13-TDPI-TAT) showed the best EL performances compared with that of the other two compounds. The doped devices of 3,8,13-TTPI-TAT exhibited a maximum luminance (Lmax) of 402 cd/m2 and a maximum external quantum efficiency (EQEmax) of 0.72%, while its non-doped devices showed Lmax of 500 cd/m2 and the EQEmax of 1.43%. It has important potential significance for the further design and synthesis of TAT derivatives with good charge transport and high EQE.

Three phenylene ethynylene derivatives substituted by arylimidazole groups (benzo[d]imidazole, d ]imidazole, phenanthro [9,10-d]imidazole d ]imidazole and pyreno[4,5-d]imidazole) d ]imidazole) at both ends were successfully synthesized and characterized for organic electroluminescence devices. The photophysical, electrochemical, and thermal stability of the compounds were systematically investigated to reveal their structure-property relationships. All compounds presented a X-shaped structure, and exhibited excellent thermal stability and intense emission in solution and solid states. Furthermore, the solution-processed doped devices using the blend of tris(4-carbazoyl-9-ylphenyl)amine (TCTA) with the phenylene ethynylene derivatives as emitting layers emitted deep-blue emission with maximum external quantum efficiency (EQEmax) max ) of 0.63 % for the benzo[d]imidazole-terminated d ]imidazole-terminated derivative and blue emission with EQEmax max of 1.93 % and 1.45 % for the phenanthro[9,10-d]imidazole- d ]imidazole- and pyreno[4,5-d]imidazole- d ]imidazole- terminated derivatives, respectively, suggesting that these compounds have a great potential as the organic emitters for deep-blue and blue devices.

Two carbazole-functionalized dibenzo[g,p]chrysene (DBC) derivatives (DBC-1 and DBC-2) were synthesized by Buchwald-Hartwig cross-coupling reaction between 3,11-dibromodibenzo[g,p]chrysene and 3,6-di-tert-butyl- carbazole or 3,3 '',6,6 ''-tetra-tert-butyl-9 ' H-9,3 ':6 ',9 ''-tercarbazole, and characterized by NMR (1H and 13C) and high resolution mass spectrometry. Their photophysical and electrochemical properties as well as thermal stabilities were investigated systematically. These compounds showed intense blue emission with photoluminescence quantum yield of 44 % and 75 % in toluene solution, respectively. By using 1,3-bis(N-carbazolyl)benzene (mCP) as the host material, the doped devices with a device structure of ITO/PEDOT:PSS (30 nm)/mCP:DBC derivative (x wt%) (25 nm)/TPBi (35 nm)/Liq (2 nm)/Al (150 nm) were fabricated to characterize their electroluminescent properties, in which the emitting layer (mCP:DBC derivative) was prepared by solution-processed method. Their devices exhibited deep-blue emission with a maximum external quantum efficiencies (EQEmax) of 1.01 % for DBC-1 and 1.90 % for DBC-2.

Two new V-shaped bis-coumarins (VBC) with the benzophenone-imbedded triptycene and carbazole, VBCCO-TTC and VBCCOCz, were synthesized and characterized by NMR (1H and 13C), high resolution mass spectrometry and elemental analysis, and their thermal stabilities and photophysical and electrochemical properties were systematically studied. They exhibited strong green emission with high fluorescence quantum yield of 90.4 % and 93.65 % in dichloromethane solution, respectively. The combination of theoretical research and experimental data revealed the structure-property relationship of the functional groups grafted onto the V-shaped bis-coumarins. Moreover, the doped devices treated with the blend of CBP:VBC derivatives as the emitting layers showed green emission, in which the VBCCOCz doped devices exhibited an maximum external quantum efficiency (EQEmax) of 2.66 %, while the VBCCO-TTC doped devices showed an EQEmax of 1.79 %, at the doping concentration of 5 wt%.

Four new organic D-pi-A fluorophores consisting of different electron donors (carbazole and diphenylamine) and acceptors (4,5-dicyanoimidazole and 5,6-dicyanobenzo[d]imidazole), d ]imidazole), i.e., DCI-Cz, , DCI-TPA, , DCBI-Cz and DCBITPA, , were synthesized to obtain deep-blue organic light-emitting diodes (OLEDs). These compounds exhibited good solubility and excellent thermal stability as well as strong deep-blue and blue emission in solution and solid states. With mCP (1,3-di(9H-carbazol-9-yl)benzene) H-carbazol-9-yl)benzene) as the host material, the doped devices with a configuration of ITO/PEDOT:PSS (30 nm)/mCP:dopant (x wt%) (25 nm)/TPBi (35 nm)/Liq (2 nm)/Al (150 nm) were fabricated by solution-processing the emitting layers to evaluate their electroluminescence (EL) performances. The devices using the blend of mCP with DCI-TPA as emitting layers exhibited the best electroluminescent performance with a maximum external quantum efficiency (EQEmax) max ) of 4.39 % and a maximum current efficiency of 3.04 cd/A.

Two spiroacridine-imidazole derivatives (SAF-BI and SAF-PI) were prepared and their potential for application in deep-blue OLEDs was explored.

Two novel naphthalimide derivatives PTZNI-Cz and PTZNI-TPA were successfully designed and synthesized, in which phenothiazine, triphenylamine and carbazole were used as electron donors and naphthalimide was used as the electron acceptor. Their photophysical, electrochemical, and thermal properties were investigated. These derivatives showed remarkable aggregation-induced emission (AIE) effect. Furthermore, the maximum emission peaks of PTZNI-Cz and PTZNI-TPA in the thin film state are at 610 nm and 623 nm respectively, which is typical of red fluorescent materials.

Two phenanthro[4,5-abc]phenazine abc ]phenazine derivatives, 11-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenanthro[4,5-abc] tert -butyl-9 H-carbazol-9-yl)phenanthro[4,5- abc ] phenazine ( PyQ-Cz ) and 4-(phenanthro[4,5-abc]phenazin-11-yl)-N,N-diphenylaniline abc ]phenazin-11-yl)- N,N-diphenylaniline ( PyQ-TPA ), were synthesized by grafting the an electron-donating carbazole and triphenylamine segments onto the pyrene-fused quinoxaline (PyQ) core, respectively and characterized by NMR (1H 1 H and 13 C) and high resolution mass spectrometry. Their thermal, photophysical and electrochemical properties were systematically investigated. These compounds exhibited excellent thermal stability and intense yellow emission and orange emission in dichloromethane solution, whereas they exhibited green emission in solid films. Based on their high photoluminescence quantum yields and the frontier orbital energies, the doped devices with a structure of ITO/PEDOT:PSS (30 nm)/CBP:PyQ PyQ derivatives (x wt%) (25 nm)/TPBi (35 nm)/Liq (2 nm)/Al (150 nm) were fabricated by solution-processed the emitting layers to investigate their electroluminescence (EL) performances, in which the doped devices of PyQCz exhibited the maximum external quantum efficiency (EQEmax) max ) of 1.86 %, while the PyQ-TPA doped devices showed an EQEmax max of 0.82 %.

Two new indolo[3,2-b]carbazole derivatives containing coumarin fluorophores (2,8-ICZ-C and 3,9-ICZ-C) were synthesized by the introduction of two 7-diethylamino-3-coumarinyl fluorophores at 2,8 -positions and 3,9 -positions of the indolo[3,2-b]carbazole (ICZ) core, respectively, as the organic emitters for organic light -emitting devices (OLEDs). The photophysical and electrochemical properties and thermal stabilities of the compounds were systematically investigated. These compounds exhibited good thermal stability as well as strong blue emission (phi f of 79.67 % for 2,8-ICZ-C and phi f of 55.90 % for 3,9-ICZ-C) in CH2Cl2 solution. The doped devices with a structure of ITO/PEDOT:PSS (50 nm)/2,6DCzPPy:ICZ derivative (x, wt%) (30 nm)/TPBi (20 nm)/Liq (3 nm)/Al (130 nm) were fabricated by solution -processed the emitting layers, in which the 2,8-ICZ-C device exhibited a maximum luminance (Lmax) of 1425 cd/m2, a maximum current efficiency (CEmax) of 1.24 cd/A and a maximum external quantum efficiency (EQEmax) of 0.71 %, and the 3,9-ICZ-C device showed Lmax, CEmax and EQEmax of 1005 cd/m2, 1.14 cd/A and 0.53 %, respectively.