Blue-emitting Host Research Articles

A blue-emitting porous MOF incorporated with red-emitting Eu(III) ions for nitro compounds fluorescence sensing: Improving ratiometric selectivity and sensitivity by synergistic effect of a dendritic auxiliary ligand

Due to the high nitrogen oxidation valence and electron-deficient structure, organic nitro compounds are generally known as potential explosive which are also considered as environmental threat. Optical sensing is an attractive quantification method with simple operation procedure and limited requirement for equipment, but traditional optical sensing platforms for nitro compounds suffered from limited sensitivity and poor selectivity. To solve this problem, this work designed applied a ratiometric sensing platform. Here red-emitting Eu(III) was incorporated into a blue-emitting host bio-MOF-1. A dendritic auxiliary ligand (denoted as BBB) was adopted to stabilize the adduct between Eu(III) and TPA (2,4,6-trinitrophenol). By so doing, the blue emission intensity from bio-MOF-1 was increased, while the Eu3+ emission intensity was minimized. The sensing behavior upon auxiliary ligand BBB was compared to that upon a reference ligand (1,10-phenanthroline). The sensing mechanism was proved as an irreversible Eu(III) leak and coordination with TPA/BBB guaranteed by BBB steric hindrance. Finally, a linear working equation with improved sensitivity (by sixfold) and unique selectivity was observed.

Three-color white electroluminescence emission using perovskite quantum dots and organic emitters

To realize a full-color display in the research field of perovskites or perovskite-structured quantum dots (PeQDs), the development of white-light-emitting devices that operate by emitting light of three primary colors (red, green, and blue) has emerged as an active research topic. In the present study, we report for the first time three-color white-light emission with high brightness from white-emitting PeQD organic light-emitting diodes (WPeQD-OLEDs) fabricated using a PeQD material and organic emitters. A WPeQD-OLED bilayer was prepared by depositing a blue-emitting organic layer on top of a CsPb(Br/I)3 QD layer mixed with N9,N10-Bis(4-(tert-butyl)phenyl)-N9,N10-Di-o-Tolylanthracene-9,10-Diamine (p-Tb-o-Me-TAD), which were spin-coated as red and green emitters, respectively. The WPeQD-OLED device was stable during operation and demonstrated emission of three primary colors. In the WPeQD-OLED device, charge carriers were distributed by an 9-(naphthalen-1-yl)-10-(naphthalen-2-yl)anthracene (α,β-ADN) blue-emitting host material with a deep highest occupied molecular orbital level. The electroluminescence (EL) spectra of the WPeQD-OLEDs showed EL maximum peaks at 460, 527, and 640 nm; the CIE color coordinates of the emitted light were (0.33, 0.40). The EL results confirmed that the maximum luminance was 49,000 cd m−2 and the maximum luminance efficiency and power efficiency were 4.48 cd A−1 and 2.16 lm W−1, respectively.

Efficient and Saturated Red Light‐Emitting Electrochemical Cells Based on Cationic Iridium(III) Complexes with EQE up to 9.4 %

Solid-state light-emitting electrochemical cells (LECs) have several advantages, such as low-voltage operation, compatibility with inert metal electrodes, large-area flexible substrates, and simple solution-processable device architectures. However, most of the studies on saturated red LECs show low or moderate device efficiencies (external quantum efficiency (EQE) <3.3 %). In this work, we demonstrate a series of five red-emitting cationic iridium complexes (RED1--RED5) with 2,2'-biquinoline ligands and test their electroluminescence (EL) characteristics in LECs. The Commission Internationale de l'Eclairage (CIE) 1931 coordinates for the LECs based on these complexes are all beyond the National Television System Committee (NTSC) red standard point (0.67, 0.33). The maximal EQE of the neat-film RED1-based LECs reaches 7.4 %. The reddest complex, RED3, is doped in the blue-emitting host complex, BG, to fabricate host-guest LECs. The maximal EQE of the host-guest LECs (1 wt % complex RED3) reaches 9.4 %, which is among the highest reported for the saturated red LECs.

Bipolar Blue Host Emitter with Unity Quantum Yield Allows Full Exciton Radiation in Single-Emissive-Layer Hybrid White Organic Light-Emitting Diodes.

Phosphorescence/fluorescence hybrid white organic light-emitting diodes (OLEDs) are highly appealing for solid-state lighting. One major challenge is how to fully utilize the electrically generated excitons for light output. Herein, an efficient strategy to realize full exciton radiation is successfully revealed by a judicious molecular design and suitable device engineering. A blue host emitter TP-PPI is designed and synthesized, exhibiting a near 100% photoluminescence quantum yield and a high triplet energy level, enabling high-performance blue fluorescence and sensitization of a yellow phosphorescent dopant. Full exciton radiation in hybrid white OLEDs is demonstrated with a single emitting layer formed by doping a yellow phosphor (PO-01) into TP-PPI. Near 100% exciton utilization and state-of-the-art external quantum efficiency of 27.5% are achieved with the high-efficiency blue-emitting host and an electron-trap engineered device architecture.

Spin-orbit coupling effects on energy transfer channel in organic semiconductors

Spin-orbit coupling (SOC) effects on energy transfer channel in polymer-phosphorescent dopant system have been investigated. The blue-emitting host polymer, poly [9, 9-di-n-hexyl-fluorenyl-2, 7-diyl] (PFO), was doped into a variety of concentrations between 0.1 and 5% with a red emissive phosphorescent dye, bis (2-[2′-benzothienyl)-pyridinato-N, C3′] iridium (acetyl-acetonate) (BtpIr). The mechanism for the SOC effects on energy transfer channel between the host and the dopant was studied using both photoluminescence (PL) and electroluminescence (EL) techniques. The SOC effect enhances enormously the intersystem crossing (ISC) rate arising by the strong overlap of the delocalized π orbitals of the PFO and BtPIr. The ISC energy transfer channel competes effectively with Fӧrster energy transfer channel and Dexter energy transfer channel. The energy transfer from S1 (PFO) state to T1 (PFO and BtPIr) state is increased by SOC. Consequently, the population of the S1 (PFO) state decreased. So the Förster energy transfer intensity is deceased. SOC leads to such an indirect decrease for the Förster energy transfer intensity. In other hand, the intensity of T1 (PFO) state increased. So the Dexter energy transfer channel intensity is increased. It allows more PFO triplets to the Dexter energy transfer channel to BtPIr triplets. The increased population of the triplet state brings about a greater number of detectable photons that are emitted from the BtPIr molecules. EL spectra implied that only a few singlets formed on the PFO contribute to the emission, most of them are transformed into triplet state by ISC channel.

发光层位置对白光有机发光二极管的影响

Two types of white organic light-emitting devices (WOLED) containing a layered light-emitting region composed of a single blue-emitting host and different fluorescent dopants (blue and orange) were fabricated. The efficiency, lifetime, brightness, spectral voltage-dependence and white balance of devices were investigated. The results show that the performance of the devices strongly depends on the stack order of two emitting layers and the thickness of the emitting layer. It is found that the WOLED with an EML sequence of orange/blue (from anode to cathode) shows better stability than that with an EML sequence of blue/orange. It is due to the rubrene in orange emitting layer that acts as hole-trap sites and captures the passing holes and hence balances the concentration of electrons and holes. The optimized white device exhibits a favorable CIE coordinates (0.3201, 0.3459) which is close to the standard white light. ©, 2015, Chines Academy of Sciences. All right reserved.

White organic light-emitting diodes with 9, 10-bis (2-naphthyl) anthracene

White organic light-emitting diodes were fabricated by 9, 10-bis (2-naphthyl) anthracene (ADN) doped with Rubrene with a structure of ITO/copper phthalocyanine (CuPc) / NPB /ADN: Rubrene /Alq3 /CsF/Mg:Ag/Ag. Multilayer organic devices using AND and Rubrene as an emitting layer produced white emissions with good chromaticity and luminous efficiency as high as 5.93 cd/A. This performance can be explained by Förster energy transfer from the blue-emitting host to the orange-emitting dopant.

Controlled light emission from white organic light-emitting devices with a single blue-emitting host and multiple fluorescent dopants

In this work, we fabricated white organic light-emitting devices (WOLEDs) containing a layered light-emitting region composed of a single blue-emitting host and different fluorescent dopant materials. The effects of varying the dye-doping ratio and emitting layer thickness on the efficiency, lifetime, spectral voltage-dependence and white balance were investigated for devices with a blue/orange stacked layer structure. Addition of a blue host layer doped with a green-emitting dopant, to give a blue/green/orange emitter, resulted in a broadband white spectrum without the need for a charge-blocking interlayer. The composition of blue, green and orange dopants in the host and the thickness of each emitting layer were optimized, resulting in a device efficiency of 9–11 cd A−1 even at a high brightness of 10 000 cd m−2 (achieved at a bias voltage of less than 9 V) with an emission spectrum suitable for lighting applications.

Blue organic light-emitting devices using novel styrylarylene host and dopant materials

Four styrylamine-based blue dopant materials were synthesized using either the Wittig–Hornor or the Heck reaction. Blue organic light-emitting diodes were successfully prepared and characterized. The organic light-emitting diodes comprised ITO/DNTPD/NPB/TPM-BiP:NBD(5%)/Alq 3/Al–LiF in which NPB was used as the hole transport layer, DNTPD as the hole injection layer, 4,4′-bis[1-phenyl-2-(4,4′-biphenyl)vinyl]- p-terphenyl (TPM-BiP) as the blue-emitting host, Alq 3 as the electron transport layer and Al as the cathode.

Synthesis and Characterization of Poly(N-arylcarbazole-alt-aniline) Copolymers as Blue-Emitting Host Matrix for Polymer Light-Emitting Diodes

Thermally stable and solution-processable poly(N-arylcarbazole-alt-aniline) copolymers with high structural integrity were synthesized in good yields via palladium-catalyzed polycondensation of aniline with corresponding N-arylcarbazole monomers such as N-(2-ethylhexyloxyphenyl)-3,6-dibromocarbazole, bis[6-bromo-N-(2-ethylhexyloxyphenyl)carbazole-3-yl] and N-(4-(2-ethylhexyl)-3,5-dibromomethylene-phenyl)carbazole, respectively. The optical and electrochemical properties of these copolymers were measured and compared with those of poly(N-alkylcarbazole-alt-aniline) copolymer. All synthesized poly(N-arylcarbazole-alt-aniline) copolymers showed maximum UV-Vis absorption peaks at around 300 nm in THF solution, and exhibited maximum photoluminescence peaks in the blue emission range from 430 to 460 nm. It was also found that poly(N-arylcarbazole-alt-aniline) copolymers had wider band gap energy than poly(N-alkylcarbazole-alt-aniline) copolymer.

SYNTHESIS AND CHARACTERIZATION OF ALTERNATING COPOLYMERS CONTAINING CARBAZOLE AND ANILINE MOIETIES

Four different types of alternating copolymers, named as poly(N-(2-ethylhexyl)-3,6-dibromo-carbazole-alt-aniline) (P1), poly(3,6-dibromo-carbazole-alt-aniline) (P2), poly(N-(3,5-dibromo-methylene-phenyl)-carbazole-alt-aniline) (P3) and poly(N-[4-(2-ethylhexyloxyl)-3,5-dibromomethylene-phenyl]-carbazole-alt-aniline) (P4) were successfully synthesized by palladium-catalyzed polycondensation of corresponding carbazole-containing dibrominated compounds and an aniline. These resulting polymers exhibited good solubility in normal organic solvents and showed relatively high molecular weights. Excellent thermal stability of the polymers was observed from TGA, showing less than 8% of weight loss on heating to 350°C under N 2 atmosphere. From UV-Vis absorption and photoluminescence spectra of these solution-processable polymers, it was observed that λ max,UV was in the range of 308 – 352 nm and λ max,PL was in the blue emission range of 450 – 463 nm. Electrochemical characteristics of these alternating copolymers were investigated to prove the potential in application for blue-emitting host matrix and hole-transporting layer in polymer light-emitting devices.