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Realization of Excitation Wavelength Independent Blue Emission of ZnO Quantum Dots with Intrinsic Defects
摘要： Eco-friendly cation metal oxide quantum dots (QDs) are one of promising candidates to replace for QDs containing expensive Indium (In) or hazardous Cd- and Pb-elements. Super-Eg excitation wavelength (λex) dependent Zni-VO complex defects related characteristic emissions of green, yellow, and orange-red from ZnO QDs are completely inhibited by reducing oxygen vacancies through the hybridization of Zn interstitials in ZnO QDs with anti-bonding O-states of graphene oxide (GO) QDs. Thus, only λex independent violet-purple-blue (V-P-B) emission resulting from transitions among Frenkel pairs (Zni 0-VZn) and the defects Zni 0-Oi in ZnO-GO QDs with a high photoluminescence quantum yield (PLQY) of 92% is successfully achieved. White-light emission from PL QD-LEDs is achieved using a mixture of ZnO and ZnO-GO QDs with CIE (0.32, 0.34) excited by a UV LEDs chip (λ=365 nm). Further, ZnO-GO QD-based deep-blue LEDs (λ=438 nm) with luminance of 1980 cd/m2, a luminous efficacy (LE) of 2.53 cd/A, and external quantum efficiency (EQE) of 2.78 % with CIE (0.16, 0.11) are also realized.
关键词： eco-friendly fluorescent materials,excitation independent deep blue light emission,photoluminescence quantum efficiency,Zni-Vo complex defects,ZnO-Graphene Oxide quantum dots
更新于2025-09-19 17:13:59
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Efficient deep blue OLEDs with extremely low efficiency roll-off at high brightness based on phenanthroimidazole derivatives
摘要： Phosphorescent and thermally activated delayed fluorescence (TADF) emitters can break through the spin statistics rules and achieve great success in external quantum efficiency (over 5%). However, maintaining high efficiency at high brightness is a tremendous challenge for applications of organic light emitting diodes. Hence, we reported two phenanthroimidazole derivatives PPI-An-CN and PPI-An-TP and achieved extremely low efficiency roll-off with about 99% of the maximum external quantum efficiency (EQEmax) maintained even at a high luminance of 1000 cd/cm2 based non-doped devices. When doping the two materials in CBP (4,40-bis(N-carbazolyl)-1,10-biphenyl), the doped devices still exhibited excellent stability at high brightness with CIEy ≤ 0.07 and low turn-on voltage of only 2.8 V. The state-of-the-art low efficiency roll-off makes the new materials attractive for potential applications. It is first time that the Fragment Contribution Analysis method has been used to analyze the excited state properties of the molecules in the field of OLEDs, which helps us understand the mechanism more intuitively and deeply.
关键词： Fragment contribution analysis,Phenanthroimidazole,Deep blue,OLED,Low efficiency roll-off
更新于2025-09-16 10:30:52
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Bipolar fluorophores based on intramolecular charge-transfer moieties of sulfone for nondoped deep blue solution-processed organic light-emitting diodes
摘要： Dipolar emitters exhibited excellent performance in organic light-emitting diode (OLED). However, these molecules had intramolecular charge-transfer (ICT) properties, which posed challenge to obtain deep blue emission. In this study, three fluorophores were designed by introducing carbazole and diphenylamine as electron donors and sulfone as electron acceptor due to their mild charge-accepting properties and twisted angles. These materials appeared almost in vertical angles of the dihedral configuration, and exhibited high thermal and electrochemical stability, suitable for solution-processed OLED. The solution-processed non-doped devices based on these three emitters were realized, where two emissions within the standard deep blue emission range were achieved with the Commission International e de l’Eclairage (CIE) coordinates of (0.16, 0.12) and (0.16, 0.15).
关键词： bipolar fluorophores,intramolecular charge-transfer,deep blue,single layer,organic light-emitting diodes
更新于2025-09-16 10:30:52
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A Silanea??based Bipolar Host with High Triplet Energy for High Efficiency Deepa??Blue Phosphorescent OLEDs with Improved Device Lifetime
摘要： A high triplet energy host is developed using silane moiety. 9-(4-(triphenylsilyl)dibenzo[b,d]furan-2-yl)-9H-carbazole (SiDBFCz) is designed through extensive density functional theory (DFT) calculations to obtain appropriate hole and electron injection barriers. The chemical hardness and the charge transport characteristics are comprehensively investigated to realize a bipolar host with high triplet energy over 2.9 eV for deep blue phosphorescent organic light-emitting diodes (PHOLEDs). The synthesized SiDBFCz clearly exhibits the bipolar characteristics especially with emitter molecules doped. An external quantum efficiency over 19% without any microcavity optimization is achieved thanks to the good charge balance in the SiDBFCz PHOLED. The device lifetime of the SiDBFCz PHOLED is improved more than 1000%, compared to the unipolar control devices at an initial luminance of 500 cd/m2. The dramatic enhancement of the operational stability of the deep blue PHOLED is also thoroughly investigated in terms of electrochemical stability of host molecules in charged or excited states. The results clearly indicate that the device lifetime is strongly correlated with the bond dissociation energy and the activation energy for the bond dissociation reaction in triplet excited state.
关键词： deep blue phosphorescent OLEDs,bond dissociation energy in triplet excited state,high triplet bipolar host,lifetime
更新于2025-09-16 10:30:52
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Violet/deep-blue fluorescent organic light-emitting diode based on high-efficiency novel carbazole derivative with large torsion angle
摘要： A novel and highly efficient violet/deep-blue fluorescent carbazole and naphthalene-based compound (1) is designed and synthesized. The compound shows intensive violet/deep-blue fluorescence, high photoluminescence efficiency (0.72 in CH2Cl2, 0.65 in film) and narrow full width at half maximum (48 nm). The large torsion angles between carbazole and naphthalene guarantee the weak intermolecular interactions and suppress the π-π interactions in solid state, resulting in the highly efficient violet/deep-blue fluorescence. The maximum emission peak, luminance and external quantum efficiency for violet/deep-blue electroluminescence are 410 nm, 1326 cd/m2 and ～2%, respectively.
关键词： Carbazole,Naphthalene,Violet/deep-blue fluorescence,Organic light-emitting diodes
更新于2025-09-12 10:27:22
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Bright high-colour-purity deep-blue carbon dot light-emitting diodes via efficient edge amination
摘要： Deep-blue light-emitting diodes (LEDs) (emitting at wavelengths of less than 450 nm) are important for solid-state lighting, vivid displays and high-density information storage. Colloidal quantum dots, typically based on heavy metals such as cadmium and lead, are promising candidates for deep-blue LEDs, but these have so far had external quantum efficiencies lower than 1.7%. Here we present deep-blue light-emitting materials and devices based on carbon dots. The carbon dots produce emission with a narrow full-width at half-maximum (about 35 nm) with high photoluminescence quantum yield (70% ± 10%) and a colour coordinate (0.15, 0.05) closely approaching the standard colour Rec. 2020 (0.131, 0.046) specification. Structural and optical characterization, together with computational studies, reveal that amine-based passivation accounts for the efficient and high-colour-purity emission. Deep-blue LEDs based on these carbon dots display high performance with a maximum luminance of 5,240 cd m?2 and an external quantum efficiency of 4%, notably exceeding that of previously reported quantum-tuned solution-processed deep-blue LEDs.
关键词： carbon dots,deep-blue LEDs,amine-based passivation,external quantum efficiency,high-colour-purity
更新于2025-09-12 10:27:22
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Bright Deep Blue TADF OLEDs: The Role of Triphenylphosphine Oxide in NPB/TPBi:PPh <sub/>3</sub> O Exciplex Emission
摘要： Very bright (≈14 000 cd m?2) deep blue exciplex organic light emitting diodes (OLEDs) peaking at ≈435 nm, where the photopic response is ≈0.033, and with CIE color coordinates (0.1525, 0.0820), are described. The OLED properties are interestingly linked to PPh3O (triphenylphosphine oxide) and attributes of the emitting layer (EML) comprising NPB interfacing host:guest TPBi:PPh3O 5:1 weight ratio. A neat PPh3O layer that is central for device performance follows the EML (NPB/TPBi:PPh3O 5:1/PPh3O). The bright electroluminescence originates from NPB/TPBi:PPh3O exciplexes involving triplets via thermally activated delayed fluorescence, as evident from the strong quenching of the photoluminescence (PL) by oxygen and interestingly, the monomolecular emission process. The transient PL decay times of a NPB/TPBi:PPh3O 5:1/PPh3O film are 43 ns in air versus 136, 610, and weak ≈2000 ns in N2. For comparison, the respective PL decay times of films of NPB:TPBi are 16 ns in air versus 131 and 600 ns in N2, and of NPB:PPh3O they are 29 ns in air versus 56, 483, and weak ≈2000 ns in N2. It is suspected that slow emitting states are associated with a PPh3O aggregate interacting with NPB.
关键词： all-organic OLEDs,exciplex TADF OLEDs,bright deep blue OLEDs
更新于2025-09-12 10:27:22
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Asymmetrically twisted phenanthrimidazole derivatives as host materials for blue fluorescent, green and red phosphorescent OLEDs
摘要： The electroluminescent properties of asymmetrically twisted phenanthrimidazole derivatives comprised of fluorescent anthracene or pyrene unit namely, 1-(1-(anthracen-10-yl)naphthalen-4-yl)-2-styryl-1H-phenanthro[9,10-d]imidazole (ANSPI), 1-(1-(pyren-1-yl) naphthalene-4-yl)-2-styryl-1H-phenanthro[9,10-d]imidazole (PNSPI), 4-(2-(4-(anthracen-9-yl) styryl)-1H-phenanthro[9,10-d]imidazol-1-yl)naphthalene-1-carbonitrile (ASPINC) and 4-(2-(4-(pyren-1-yl)styryl)-1H-phenanthro[9,10-d] imidazol-1-yl)naphthalene-1-carbonitrile (PSPINC) for blue OLEDs have been analyzed. The asymmetrically twisted conformation interrupt π-conjugation effectively results in deep-blue emission. The pyrene containing PSPINC based non-doped blue device (476 nm) shows maximium efficiencies (current efficiency (ηc)-4.23 cd/A; power efficiency (ηp)-2.86 lm/W; external quantum efficiency (ηex)-3.48%: CIE (0.16, 0.17) at 3.10 V. Among the doped blue devices, An(PPI)2:ASPINC shows high efficiencies (ηc-12.13 cd/A; ηp-5.98 lm/W; ηex-6.79%; L-23986 cd m?2; EL-458 nm) at 3.15 V with CIE (0.15, 0.17) than An(PPI)2:PSPINC based device which is inconsistent with non-doped device performances. The green and red PhOLEDs show higher efficiencies with Ir(ppy)3: ASPINC (ηc-50.6 cd/A; ηp-53.4 lm/W; ηex-17.0%; L-61581 cd m?2; EL-501 nm, CIE (0.31, 0.60) at 3.32 V and (bt)2Ir(dipba): ASPINC (ηc-15.2 cd/A; ηp-16.5 lm/W; ηex-14.5%; L-13456 cd m?2; EL-610 nm), CIE (0.63, 0.36) at 3.20 V, respectively. The complete energy transfer between the host and dopant molecules improved the efficiency of PHOLEDs.
关键词： asymmetrically twisted phenanthrimidazole derivatives,electroluminescent properties,energy transfer,blue OLEDs,deep-blue emission
更新于2025-09-11 14:15:04
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45.4: High Performance of Deep Blue OLEDs with Thermally Activated Sensitized Fluorescence Technology
摘要： The low efficiency of blue devices has been a bottleneck problem for OLED panel manufacturers for a long time. In this paper, we present the development of TASF materials technology for deep blue OLEDs with high Blue Index (current efficiency/CIE-y) around 300 at CIE-y=0.078 obtained at 1000 cd/m2.
关键词： TADF,TASF,high-efficiency,Thermally Activated Delayed Fluorescence,Thermally Activated Sensitized Fluorescence,deep blue,OLED
更新于2025-09-11 14:15:04
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Decrease of intermolecular interactions for less-doped efficient deep blue monomer light-emitting diodes
摘要： Intermolecular interactions arise from molecular aggregation and cause concentration quenching and excimer emission. Although aggregation or excimer induced emission are sometimes favored, for example for color tuning, intermolecular interactions should usually be minimized because concentration quenching and excimer emission usually result in poor efficiency and color instability. In this paper, two novel tert-butyl modified naphthyl derivates, 4,5'-di-{[N,N,N',N'- tetrakis-(4-tert-butyl-phenyl)]phenyl-1'',4'''-diamine}-1,1'-binaphthalenyl (BN5) and 1,5-di-{[N,N,N', N'-tetrakis-(4-tert-butyl-phenyl)]phenyl-1'',4'''-diamine}-3,7-bi-tertbutylnaphthalenyl (BN6), have been synthesized and their intriguing photophysical properties and high-efficiency deep-blue electroluminescence (EL) in less-concentrated condensed phase investigated. Electroluminescent devices based on BN5 in 50% matrix achieved a high external quantum efficiency (EQE) of 3.7% and the Commission Internationale de L’Eclairage (CIE) coordinates of (0.160, 0.081) which is very close to the National Television Standards Committee’s (NTSC of USA) pure blue standard. Meanwhile, the non-doped device based on BN5 demonstrated a much higher EQE of 4.5%. Neat BN6-based device presented a pure monomer emission (λpeak = 420 nm) with an extremely high EQE of 5.1% and a satisfactory CIE coordinate of (0.171, 0.076). Such values are the best ever reported for 420 nm EL emission with an un-doped layer. We attributed the enhanced performance of deep blue monomer light-emitting diodes to tert-butyl groups of BNs due to a reduction of intermolecular interaction, especially the tert-butyl substituents on the molecular backbone of BN6 play a major role in inhibiting dimer and crystallization-induced emission.
关键词： excimer emission,organic light-emitting diodes,deep blue,intermolecular interactions
更新于2025-09-11 14:15:04