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Triplet-triplet annihilation effects in rubrene/C60 OLEDs with electroluminescence turn-on breaking the thermodynamic limit
摘要： Recently, Engmann et al. experimentally and theoretically examined the higher-order effects in rubrene/C60 organic light-emitting diodes (OLEDs), claiming that triplet-triplet annihilation (TTA) is not responsible for the electroluminescence (EL) with extremely-low turn-on voltage (Voc). Instead, the evidence from the equivalent circuit fitting suggest that the direct band-to-band recombination can interpret the low voltage phenomena. However, at applied bias of about 1.0 V, the excitons prefer to form on the charge-transfer state between rubrene/C60 interface. Direct singlet formation on rubrene and direct band-to-band recombination seems impossible to be accountable for such low Voc.
关键词： thermodynamic limit,electroluminescence,rubrene/C60 OLEDs,triplet-triplet annihilation
更新于2025-09-19 17:13:59
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Highly efficient deep-red/near-infrared D-A chromophores based on naphthothiadiazole for OLEDs applications
摘要： Donor-acceptor (D-A) chromophores are an important class of deep-red/near-infrared (DR/NIR) materials. However, efficient D-A DR/NIR fluorescent emitters are rare due to the intrinsic charge-transfer excited-state. In this paper, two novel D-A-type DR/NIR fluorescent emitters with triphenylamine (TPA, donor), naphthothiadiazole (NZ, acceptor), pyrimidine (2TPA-NZN) and benzene (2TPA-BZN) as the π-bridge, are designed and synthesized. The photophysical study and theoretical analysis revealed that the emissive-state of the two materials has hybridized local and charge-transfer (HLCT) characters. This characteristic caused high photoluminescent quantum yield (PLQY) both in solution and doped film. The 2TPA-BZN with a more rigid molecular structure exhibits a lower non-radiative rate constant (knr), resulting in relatively higher PLQY as compared with the 2TPA-NZN. The doped organic light-emitting diodes (OLEDs) devices based on these materials demonstrated excellent maximum external quantum efficiency (EQEmax > 5.0 %) and the emission peak around 665 nm.
关键词： DR/NIR materials,OLEDs,HLCT,Naphthothiadiazole,D-A Chromophores
更新于2025-09-19 17:13:59
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Asymmetric anthracene derivatives as multifunctional electronic materials for constructing simplified and efficient non-doped homogeneous deep blue fluorescent OLEDs
摘要： Herein, large π-conjugated core anthracene with an innate bipolar property was employed to construct multifunctional organic electronic materials. Delicate manipulating molecules via combining anthracene core and large periphery groups, two asymmetric anthracene derivatives namely (4-(10-(4-(9H-1,5-diazacarbazole-9-yl)phenyl)anthracen-9-yl)phenyl)diphenylphosphine oxide (p-PO15NCzDPA) and (3-(10-(3-(9H-1,5-diazarcarbazole-9-yl)phenyl)anthracen-9-yl)phenyl)diphenylphosphine oxide (m-PO15NCzDPA) were firstly designed and developed. The large periphery groups 1,5-diazarcarbazole (15NCz) and diphenylphosphine oxide (PO) efficiently interrupt the intramolecular π-conjugation, presenting an asymmetric bulky periphery enveloping strategy achieving highly twisted structures, which help to realize deep-blue emission. Meanwhile, due to the high PLQY and well-balanced bipolar transport characteristics, desired device addressing the contradiction of efficiency, color gamut and structure complexity is within reach. Detailed device engineering study was carried out, in which p-PO15NCzDPA and m-PO15NCzDPA were functioned as multifunction layers. As expected, p-PO15NCzDPA-based homogenous and unilateral homogenous OLEDs exhibited outstanding performance with impressive EQEmax of 4.55% and 6.40%, deep blue CIE coordinates of (0.152, 0.075) and (0.151, 0.066) at the voltage of 6 V, narrow FWHM of 46 nm and 50 nm, respectively. More importantly, the simplified homogenous device achieved extremely low efficiency roll-offs of 1.3% and 4.8% at 1000 and 5000 cd m-2, respectively. These results are among the most outstanding performance, which provided a guide for further improving the performance of deep blue fluorescent OLEDs and simplifying the structure of OLEDs.
关键词： asymmetric anthracene derivatives,homogenous device structure,multifunctional materials,deep-blue emission,fluorescent OLEDs
更新于2025-09-19 17:13:59
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Thermally Activated Delayed Fluorescence Benzyl Cellulose Derivatives for Nondoped Organic Light-Emitting Diodes
摘要： Thermally activated delayed ?uorescence (TADF) benzyl cellulose derivatives (TBC-X), which contained both carbazole (host) and phthalimide-based TADF dye (guest) moieties, were prepared from 2,3-di-O-benzyl cellulose in high yields. The TBC-X samples were soluble in common organic solvents such as CH2Cl2, CHCl3, THF, and toluene. The photoluminescence spectra of TBC-X spin-coated ?lms had a single emission peak derived only from guest moieties, which indicated e?cient energy transfer from the host to guest moieties. The TBC-10 (with a content of host and guest moieties of 93 and 7, respectively) in a spin-coated ?lm had the highest photoluminescence quantum yield of 55.3% and TADF characteristics. A nondoped organic light-emitting diode with TBC-10 as the emitting layer showed green emission (λ EL = 517 nm) and achieved a maximum external quantum e?ciency of 5.9%.
关键词： Thermally activated delayed ?uorescence,TADF,organic light-emitting diodes,benzyl cellulose derivatives,OLEDs
更新于2025-09-19 17:13:59
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Inkjet printing multilayer OLEDs with high efficiency based on the blurred interface
摘要： Inkjet printing technology is considered to be the next generation manufacturing method for organic light-emitting diodes (OLEDs) production because of its simplicity and low cost. However, the dissolution at interfaces in printing process is still one of the great challenges that limits its progress. The present work utilized the dissolution phenomenon innovatively to generate blurred interface during inkjet printing of multi-layer OLEDs, where TAPC and TAPC:TPBi:Ir-complexes were employed as hole transport layer (HTL) and emitting layer (EML) and both of them were dissolvable in butyl benzoate to form the HTL and EML inks. When they were printed sequentially, a blurred interface between HTL and EML was formed because the dissolution phenomenon, which facilitated the exciton formation and charge balance in EML and improved the device performance. With this blurred interface, the maximum current efficiency of 9.8 cd A-1, the maximum power efficiency of 5.0 lm W-1, and the maximum external quantum efficiency of 3.0% were achieved in (fpbt)2Ir(acac) based OLEDs. In contrast, they were only 7.4 cd A-1, 3.9 lm W-1 and 2.2% in devices having a clear interface between HTL and EML.
关键词： organic light emitting diodes (OLEDs),blurred interface,inkjet printing
更新于2025-09-19 17:13:59
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Recent Development in Optoelectronic Devices || Introductory Chapter: Iridium Complexes as Organic Light Emitting Diodes (OLEDs): A Theoretical Analysis
摘要： A specific discipline of electronics, which focus on light-emitting or light-detecting devices, the term “Optoelectronics” is used in the broader perspective. Such devices include those that emit light (LEDs and light bulbs), channel light (fiber optic cables), detect light (photodiodes and photoresistors), or are controlled by light (optoisolators and phototransistors). An interesting combination of electronics and optics, Optoelectronics find varied applications in telecommunications, military services, medical field, solid state devices (sensors, IR emitters, and laser emitters), and automatic control systems. The other counterparts as photo resistors and photovoltaic devices are also used for various applications. Nowadays, photodetectors has confronted significant challenges regarding the realization of efficient and sensitive detection with low-noise for the ultraviolet (UV), visible, and infrared regimes of electromagnetic spectrum.
关键词： OLEDs,Optoelectronics,Phosphorescent Emission,Iridium Complexes,Theoretical Analysis
更新于2025-09-19 17:13:59
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Exciplexa??Based Organic Lighta??Emitting Diodes with Neara??Infrared Emission
摘要： Near-infrared exciplex can weaken molecular design difficulties, and has the advantage of easy bathochromic-shift spectra via selecting the suitable electron donors and acceptors. In this contribution, exciplex is applied to fabricate near-infrared (NIR) organic light-emitting diodes (OLEDs) incorporating a synthesized fluorescent material 3-([1,1″:3′,1″-terphenyl]-5′-yl)acenaphtho[1,2-b]pyrazine-8,9-dicarbonitrile (APDC-tPh) and a commercially available material 4,4′,4″-tris(carbazol-9-yl)triphenylamine (TCTA). The device having a mixed TCTA:APDC-tPh as an emitting layer shows a 730 nm NIR emission with a maximum external quantum efficiency (EQE) of about 0.1%, while the device having 2-[4-(diphenylamino)phenyl]-10,10-dioxide-9H-thioxanthen-9-one (TXO-TPA):APDC-tPh as the emitting layer exhibits an emission peak of 704 nm with a maximum EQE of 1.27%. These results prove the feasibility of fabricating the efficient exciplex-based NIR OLEDs.
关键词： donors and acceptors,near-infrared OLEDs,exciplexes,bathochromic shifts
更新于2025-09-19 17:13:59
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Substitutional effect of different bridging groups on optical and charge transfer properties of small bipolar molecules for OLEDs
摘要： In this work, a series of eight different bipolar molecules were designed and calculated using density functional theory (DFT) and time‐dependent functional theory (TD‐DFT) for organic light emitting diodes (OLEDs) as efficient luminescent and charge transfer materials. The eight donor‐π‐donor type small molecules (D1‐D8) were composed of triphenylamine (TPA) donor (D) unit connected to 1,8‐naphthalimides (NI) acceptor (A) unit though different π‐conjugated or R‐groups (as π‐spacer). The effect of substitutions made in π‐spacer was investigated on optical, electronic, and stability properties. This calculation analysis showed that different substitutions in π‐spacer resulted smaller Eg (range from 1.63 to 2.00 eV), broader absorption with the lowest excitation energy covering both visible and near infrared regions of solar spectrum, especially D3, D4, D5, and D6 molecules. The analyses of local densities of states, frontier molecular orbitals, and natural population analysis of orbitals revealed that studied molecules exhibited π‐π* electronic transitions of absorption in singlet excited states, but D5 and D6 also show intramolecular charge transfer (ICT) characteristics. The study of chemical indices, molecular electrostatic potential (MEP) surfaces, and charge transfer properties turned out that D4, D5, and D6 are expected to show good potential for luminescent and hole transport materials in the favor of OLEDs.
关键词： DFT,organic light emitting diodes (OLEDs),optical properties,absorption spectra,electronic structures
更新于2025-09-19 17:13:59
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Theoretical Studies of Photophysical Properties of Da????a??Aa????a??D-Type Diketopyrrolopyrrole-Based Molecules for Organic Light-Emitting Diodes and Organic Solar Cells
摘要： A series of D–π–A diketopyrrolopyrrole(DPP)-based small molecules were designed for organic light-emitting diode(OLEDs) and organic solar cell(OSCs) applications. Applying the PBE0/6-31G(d,p) method, the ground state geometry and relevant electronic properties were investigated. The first excited singlet state geometry and the absorption and fluorescent spectra were simulated at the TD-PBE0/6-31G(d,p) level. The calculated results revealed that the photophysical properties were affected through the introduction of different end groups. Furthermore, the electronic transitions corresponding to absorption and emission exhibited an intramolecular charge transfer feature. Our results suggest that the designed molecules acted not only as luminescent for OLEDs, but also as donor materials in OSCs. Moreover, they can also be used as potential electron transfer materials for OLEDs and OSCs.
关键词： photophysical properties,organic solar cells(OSCs),organic light-emitting diodes(OLEDs),diketopyrrolopyrrole(DPP)-based molecules,Charge transporting property
更新于2025-09-19 17:13:59
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High triplet energy materials for efficient exciplex-based and full-TADF-based white OLEDs
摘要： Materials with high triplet energies have attracted great attention for their application in exciplex-based or thermally activated delayed fluorescence-based organic light-emitting diodes. To study the correlation between triplet energy and chemical structure, six compounds with typical donor-acceptor-donor structures were designed, synthesized, and characterized. Through the adjustment of molecular configuration by weakening the strengths of donors and increasing the angles between donors and acceptors, the triplet energies of the materials were gradually increased from 2.5 to 3.0 eV. Three exciplex-based organic light-emitting diodes containing one of the synthesized compounds were fabricated, which exhibited efficient blue, green-yellow, and white thermally activated delayed fluorescence. Blue and green-yellow organic light-emitting diodes exhibited the maximum external quantum efficiencies of 9.1% and 8.3%, respectively. White organic light-emitting diodes showed turn-on voltage of 4.8 V, high maximum luminance of 18474 cdm-2, and maximum external quantum efficiency of 10.6%. Maximum external quantum efficiencies of blue and white organic light-emitting diodes were close to the record values observed for all-exciplex-based blue and white organic light-emitting diodes.
关键词： full-TADF-based,exciplex-based,High triplet energy materials,white OLEDs
更新于2025-09-19 17:13:59