Blue-light Material Research Articles

High brightness blue electroluminescence of diamond/TmF3/LiF/TmF3 composite film

Although GaN-based blue light materials have been widely used in the field of optoelectronics, due to the high cost of preparation, and the emission wavelength of GaN-based devices will be easily affected by temperature and other external environment. Therefore, the development of other types of blue EL devices becomes another important option. In this paper, diamond/TmF3 composite film (DTCF) and diamond/TmF3/LiF/TmF3 composite film (DTLTCF) electroluminescent (EL) devices were fabricated on highly doped p-type silicon substrates. And experimental results show that the EL spectrum of DTCF device shows three peaks appear at 416 nm, 456 nm and 676 nm, while the EL spectrum of DTLTCF device only exhibits two strong peaks at 416 nm and 456 nm in the blue region. At the same time, the maximum luminous intensity of DTLTCF device is 2.5 times that of DTCF device, and the brightness can reach 25 cd/m2. The luminescence mechanism of DTCF and DTLTCF devices is discussed, and the mechanism of enhancing blue light emission and inhibiting red light emission by LiF layer is explained reasonably.

Blue Organic Light Emitting Diode Materials based on Different Light-emitting Groups

Abstract: Organic light emitting diode (OLED) is a device that uses organic semiconductor materials to emit light under the action of an electric field. Compared with traditional luminescent materials, they have the advantages of good softness, low-temperature resistance, wider field of vision and low energy consumption, and have been widely used in the field of display and lighting in recent years. In addition, compared with red and green light-emitting materials, the maximum external quantum efficiency of blue-light materials-based devices is high, but the CIE coordinate performance is poor and the blue emission is difficult to achieve high efficiency and high color purity at the same time. Researchers continue to design new molecular structures in order to synthesize new high-efficiency blue light materials. It is found that different molecular structures have different effects on the performance of OLED devices. In the design and synthesis of blue-light materials, various light-emitting groups are often used to regulate the stability, singlet-third-line state of the target molecule energy level difference, excited state lifetime, aggregation state structure, electricity luminescent color and its OLED performance, etc. The introduction of different lightemitting groups into the blue light material greatly improves the performance of the material. This paper mainly reviews the research status of blue organic electroluminescent materials in the past five years from different molecular structures, further discusses the photoelectric properties of each compound and the properties of devices based on this material, and briefly analyzes the advantages of molecular design and device production. And finally discusses the improvement methods of blue OLED light-emitting materials in order to provide a reference for future research.

Blue Emission of Tetrafluorobenzocarbazole Under the Interactions of Nitrogen-oxygen Saturated hydrogen Bonds with Aggregated Proton Acid.

Two novel tetrafluorobenzocarbazole and containing the amino branch introduced at the end of the molecule are synthesized by a simple method. The tetrafluorobenzocarbazole as the electron donor with electron-rich fluoride ions connected by π-benzyl ring conjugation structure, which affects the overall electron cloud density. Moreover, the amino branch introduced at the end of the molecule, which makes it easy to form intermolecular hydrogen bonds and affected photophysical properties. Meanwhile, the photophysical property of both compounds are discussed under different acidic conditions. The UV-absorption show that around ~286nm is mainly attributed to the strong structural absorption band peak of the π-π ∗ transition of the carbazole moiety, and the irregular absorption band around ~314nm and ~326nm are mainly attributed to the n-π ∗ transition of the carbazole group conjugate with the adjacent molecule. The emission spectrum of both compounds showed that the intensity of fluorescence decreased in different degrees after the addition of the acidic solution. Furthermore, the electrochemical properties were evidenced by cyclic voltammetry (CV) and density functional theory (DFT) calculations, and the orbital conformation (HOMOs-LUMOs) was simulated by Gaussian 09 software and its crystal structure was observed by X-ray diffraction (XRD). The results exhibited that both compounds are electrochemically stable blue small-molecule fluorescent substances, and expected that both compounds can be novel and stable acid-sensitive organic blue-light materials.

Research on Fe(NH<sub>2</sub>trz)<sub>3</sub>·(BF<sub>4</sub>)<sub>2</sub> doped polyfluorene organic light-emitting devices

Since the breakthrough by Tang et al. in 1987, organic light-emitting devices (OLEDs) have attracted extensive attention in the industries and academic research communities. OLEDs have many promising characteristics, such as self-illumination, lower power consumption, easy fabrication and so on. It has a broad development prospect in high resolution display and other fields. For RGB color OLED display technology, blue light organic material is very important. Polyfluorene (PFO) is a kind of rigid planar biphenyl structure compound in all kinds of OLEDs blue light materials. However, PFO has a very big disadvantage: the long wave shift of the light-emitting peak of the electroluminescent device will produce the green light-emitting band that should not have appeared. This seriously affects the saturation color purity of PFO devices, and also seriously restricts the industrialization process. In this paper, the molecular magnetic material [Fe(NH<sub>2</sub>trz)<sub>3</sub>· (BF<sub>4</sub>)<sub>2</sub>] is used to solve this problem. ITO/PEDOT:PSS (30 nm)/PFO:Fe(NH<sub>2</sub>trz)<sub>3</sub>·(BF<sub>4</sub>)<sub>2</sub> (65 nm)/CsCl (0.6 nm)/Al (120 nm) devices were fabricated on ITO glass substrate. It is the first time to report the strong pure blue emission of PFO by using the special electronic spin state modulation of Fe(NH<sub>2</sub>trz)<sub>3</sub>·(BF<sub>4</sub>)<sub>2</sub>. The influence of Fe(NH<sub>2</sub>trz)<sub>3</sub>·(BF<sub>4</sub>)<sub>2</sub> on the photoelectric properties of PFO was studied in detail by analyzing the PL and EL characteristics of PFO and PFO:Fe(NH<sub>2</sub>trz)<sub>3</sub>·(BF<sub>4</sub>)<sub>2</sub>. Under the bias voltage of 4 V to 9 V, the device without doping Fe(NH<sub>2</sub>trz)<sub>3</sub>·(BF<sub>4</sub>)<sub>2</sub> emits very strong green light. The central peak wavelength is 553 nm, and the color coordinates are (0.33, 0.45). Moreover, with the constant change of voltage, the green light-emitting band is always much larger than the blue light-emitting band. However, the obvious difference is that Fe(NH<sub>2</sub>trz)<sub>3</sub>·(BF<sub>4</sub>)<sub>2</sub> doped device emits strong blue light, the peak wavelength is 438 nm, and the color coordinates (0.23, 0.22), which is completely consistent with the peak wavelength of the PL spectrum of the PFO film; the green light-emitting band of the PFO is successfully suppressed; with the change of the electric voltage, the proportion of the blue light part of the device spectrum in the whole EL spectrum is almost unchanged. The photoconductivity effect of undoped Fe(NH<sub>2</sub>trz)<sub>3</sub>·(BF<sub>4</sub>)<sub>2</sub> device is further studied by means of the integrated opto-electro-magnetic measurement technology. Under different bias voltage, it is found that there is almost no excimer in PFO:Fe(NH<sub>2</sub>trz)<sub>3</sub>·(BF<sub>4</sub>)<sub>2</sub>. This study solves the problem of green light of polyfluorene, which has puzzled the industry for many years, and provides a reliable way for the industrialization of polyfluorene used in blue OLED. The mechanism of Fe(NH<sub>2</sub>trz)<sub>3</sub>·(BF<sub>4</sub>)<sub>2</sub> blocking the abnormal green emission of PFO was discussed by using the theory of luminescence dynamics.

Experimental study on bone defect repair by BMSCs combined with a light-sensitive material: g-C3N4/rGO

Bone marrow mesenchymal stem cells (BMSCs), as seed cells, have played an important role in bone defect repair. However, efficiently amplifying and inducing BMSCs in vitro or vivo remains an urgent problem to be solved. Electrical stimulation has been beneficial to the proliferation and differentiation of BMSCs, but current electrical stimulation methods have a critical disadvantage in that they usually burn the skin. g-C3N4/rGO, a new photosensitive material, can produce photocurrent under natural light irradiation, thus reducing energy consumption. Our purpose was to explore whether this photocurrent can promote the proliferation and differentiation of BMSCs. g-C3N4/rGO synthesised under high temperature and pressure had negligible cytotoxicity as confirmed by methyl thiazolyl tetrazolium to BMSCs. Better osteogenesis was found in the blue light material group than in the light-shielding material group, exhibited by alizarin red staining, alkaline phosphatase activity, Western-Blot, and RT-qPCR. Animal experiments showed that the bone repair potential of the material group was significantly higher than that of the non-material group. Overall, we conclude that g-C3N4/rGO is a new non-toxic photosensitive material which can rapidly induce BMSCs into osteoblasts, accelerating bone regeneration and providing us with a feasible method of rapid bone repair.

Flexible Thin Film and Bulk Switchable Relaxor Coexisting Most Optimal 473 nm Blue Light without Blue-Light Hazard/Visual Injury

Blue-light hazard in display will become a more serious problem because the wearable period is coming. Visual injury caused by the short wavelength is always the biggest challenge in red/green/blue ones. Therefore, the 470–475 nm is the most needed wavelength range to balance the visual injury and display effects. In addition, the combination of suitable wavelength, flexibility, and optic–electric coexistence has triggered a huge challenge in the wearable period to explore new blue-light materials. Under this epochal premise, lead-free blue light was introduced to form a dual photoelectric dielectric/blue-light switching flexible film/bulk crystal [Habf]2[ZnCl4]·2H2O (1) (Habf = p-ammonium benzene formamide), which will be a new breakthrough in photoelectric wearable devices. The coexistence of dielectric relaxation and high quantum yield in the most ideal emission wavelength facilitates the exploration of blue-light materials with low hazard, optical–electric response, and wearable characteristics in dis...

Theoretical investigation on the effect of the modification of 2-phenylpyridine ligand on the photophysical properties for a series of iridium(III) complexes with carbazate ancillary ligands

The density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods have been used to study the electronic structure, absorption and emission spectra, charge injection/transport ability and phosphorescence quantum efficiency of a series of cyclometalated iridium(III) complexes with carbazate ancillary ligands. Complexes 2–5 introduce electron-withdrawing group sulfuryl fluoride (–SO2F) on benzene ring of ppy (2-phenylpyridine) ligands to increase the steric effect. The introduction O, S atoms and C˭C double bond increases the conjugated degree of complexes. Compared with experimental complex 1, the absorption/emission spectra of complexes 2 and 3 are blueshifted. Complexes 2 and 5 have better charge transporting ability. Complexes 3 and 6 may possess higher quantum efficiency and better hole and electron injection ability, and complex 3 could be the potentially efficient blue light materials.

A Study on Effects of Hole Blocking and Luminescence Characteristics of Blue-Light Material DPVBi on Performance of Organic Electroluminescent Devices

A Study on Effects of Hole Blocking and Luminescence Characteristics of Blue-Light Material DPVBi on Performance of Organic Electroluminescent Devices

Surface‐Oxidation‐Controlled Synthesis of Blue Fluorescence Wavelength‐Tunable Mini‐Size Carbon Nitride Nanosheet and Its Application

AbstractDeveloping highly efficient, stable, and saturated blue emitting polymer is essential in display and lighting applications and has long been a challenge. In this study, blue fluorescence wavelength‐tunable mini‐size carbon nitride nanosheets (MCNNSs) are successfully synthesized via surface oxidation polyethyleneimine (PEI) without introducing any external solvent. A simple closed container is constructed at high temperature for the controlled oxidation of PEI effectivelly. The obataind fluorescence quantum yields (QYs) of MCNNSs are up to 35% by using quinine sulfate (QY: 54%) in 0.10 M H2SO4 as a reference. More importantly, the tunable width of blue fluorescence emission wavelengths is about 50 nm ranging from 414 to 461 nm, which can be realized through change temperature. Additionally, an obvious blue fluorescence is found in PEI solutions at low temperature even at 50 oC under UV riddiation. According to surface oxidation of PEI, the MCNNSs have been applied in fluorescence image of HeLa cell. Meantime, a paper‐based new information encryption strategy is developed using MCNNSs, and a correct code “2017” is visualized only after baking the encryption paper at 100 oC under 365 nm excitation. These investigations will shed light on the use of MCNNSs in bioimaging and information encryption, as well as blue light materials used in OLED.

Synthesis and properties of blue luminescent bipolar materials constructed with carbazole and anthracene units with 4-cyanophenyl substitute at the 9-position of the carbazole unit.

With carbazole and p-cyanobromobenzene as raw materials, 4-(3,6-di (anthracen-9-yl)-9H-carbazol-9-yl)benzonitrile (DACB) and 4-(3,6-bis(anthracene -9-ylethynyl)-9H-carbazol-9-yl)benzonitrile (BACB) were synthesized through the Suzuki coupling reaction and the Sonogashira coupling reaction, respectively. These structures were characterized using 1 H nuclear magnetic resonance (NMR), elemental analysis and mass spectrometry. Their thermal properties, ultraviolet-visible (UV-vis) absorption, fluorescence emission, fluorescence quantum yields and electrochemical properties were also investigated systematically. In addition, a electroluminescence (EL) device was made with BACB as the emitting layer and performance of the EL device was studied. Results showed that: (1) the temperature points with 5% and 10% of DACB weight loss were 443°C and 461°C, respectively, and were 475°C and 506°C with BACB weight loss of 5% and 10%, respectively. When the temperature was 50-300°C, no significantly thermal transition was observed which suggested that they had excellent thermal stability. (2) DACB and BACB had single emission peaks at 415nm, and 479nm with fluorescence quantum yields of 0.61 and 0.87, respectively, indicating that both compounds could emit strong blue light. (3) According to electrochemical measurement on BACB and DACB, their gaps were 3.07eV and 2.76eV, respectively, which further showed that these two compounds were very stable and acted as efficient blue light materials. (4) The turn-on voltage of the device was 5V, and the device emitted dark blue light with Commission Internationale de L'Eclairage (CIE) coordinates of (0.157, 0.079).

A novel 3D zinc metal–organic framework based on the tetrazole-containing ligand and tricarboxylic acid

A novel zinc metal–organic framework (MOF) with the combination of 5,5′-(1,4-phenylene)bis(1H-tetrazole) (H2BDT) and 1,3,5-benzenetricarboxylic acid (H3BTC) as the mixed ligands, namely [Me2NH2]4Zn2(BDT)(BTC)2 2DMF (1), has been solvothermally synthesized and characterized. Single-crystal X-ray analysis reveals that the structure of 1 features a pillared-layered three-dimensional (3D) anionic framework of [Zn2(BTC)2(BDT)]n4n−. The luminescent property studies indicated that 1 might be a potential blue-light material. It was found that the introduction of H3BTC could exhibit an obvious influence on the luminescence of 1, which can help us in better designing luminescent MOF materials.

Novel Br-DPQ blue light-emitting phosphors for OLED.

A new series of blue light-emitting 2,4-diphenylquinoline (DPQ) substituted blue light-emitting organic phosphors namely, 2-(4-methoxy-phenyl)-4-phenyl-quinoline (OMe-DPQ), 2-(4-methyl-phenyl)-4-phenylquinoline (M-DPQ), and 2-(4-bromo-phenyl)-4-phenylquinoline (Br-DPQ) were synthesized by substituting methoxy, methyl and bromine at the 2-para position of DPQ, respectively by Friedländer condensation of 2-aminobenzophenone and corresponding acetophenone. The synthesized phosphors were characterized by different techniques, e.g., Fourier transform infra-red (FTIR), differential scanning calorimeter (DSC), UV-visible absorption and photoluminescence spectra. FTIR spectra confirms the presence of chemical groups such as C=O, NH, or OH in all the three synthesized chromophores. DSC studies show that these complexes have good thermal stability. Although they are low-molecular-weight organic compounds, they have the potential to improve the stability and operating lifetime of a device made out of these complexes. The synthesized polymeric compounds demonstrate a bright emission in the blue region in the wavelength range of 405-450 nm in solid state. Thus the attachment of methyl, methoxy and bromine substituents to the diphenyl quinoline ring in these phosphors results in colour tuning of the phosphorescence. An electroluminescence (EL) cell of Br-DPQ phosphor was made and its EL behaviour was studied. A brightness-voltage characteristics curve of Br-DPQ cell revealed that EL begins at 400 V and then the brightness increases exponentially with applied AC voltage, while current-voltage (I-V) characteristics revealed that the turn on voltage of the fabricated EL cell was 11 V. Hence this phosphor can be used as a promising blue light material for electroluminescent devices.

Two new organic borates with the large [B14O20(OH)6]4− oxoboron clusters

Two new borate clusters, [NH3(CH2)3NH3]2[B14O20(OH)6] (1) and [NH3(CH2)6NH3]2[B14O20(OH)6] (2), have been made under solvothermal conditions and characterized by single-crystal X-ray structural analysis. Also their IR and UV–Vis spectroscopy, thermogravimetric analysis, and elemental analysis have been investigated, respectively. Crystal data for 1: triclinic, P-1, a = 8.8049(4) A, b = 9.1585(5) A, c = 10.1912(5) A, α = 74.925(4)°, β = 80.987(4)°, γ = 67.495(5)°, Z = 1. Crystal data for 2: triclinic, P-1, a = 9.2010(4) A, b = 9.8663(4) A, c = 11.4191(4) A, α = 107.014(4)°, β = 92.514(3)°, γ = 107.265(4)°, Z = 1. The structures consist of isolated 8-membered boron ring made of the [B7O10(OH)3]2−cluster subunits. UV–Vis spectral investigation indicates that they are wide-band-gap semiconductors. Fluorescence spectroscopy indicates that they are potential blue light materials.

A three-dimensional highly stable cobalt(II) metal–organic framework based on terephthalic acid: synthesis, crystal structure, thermal and physical properties

A metal–organic framework complex, [Co(μ3–tp)(μ2−pyz)]n, where H2tp = 1,4-benzenedicarboxylic acid (terephthalic acid) and pyz = pyrazine, has been synthesized under hydrothermal conditions and characterized by physico-chemical and spectroscopic methods, thermogravimetric analysis and single-crystal X-ray diffraction. Each Co(II) center is surrounded by four carboxylate oxygen atoms from three tp ligands and two nitrogen atoms from two pyrazine ligands, giving a distorted octahedral geometry. The entire framework is made up of two-dimensional sheets of dicobalt ions linked via terephthalate ligands to form rectangles. The sheets are then linked into each other via the axial pyrazine ligands, forming an interlocked 3-D network, which is finally arranged as an ABAB interconnected pattern. Photoluminescence measurements for the polymer in the solid state show an emission at 414 nm, which suggests this complex as a potential blue-light material. The electrochemical behavior of a modified carbon paste electrode prepared from the complex has been studied by cyclic voltammetry, indicating quasi-reversible redox behavior.

High Brightness Blue Luminescent Material with Hole-Transporting Ability of 9-(pyren-1-yl)-9H-Carbazole

A novel bifunctional blue-light material, 9-(pyren-1-yl)-9H-carbazole (CzPy), has been synthesized and its structure is identified by electron ionization mass spectrometry, 1H NMR, and element analysis. The absorption, photoluminescence spectra and thermal properties were studied, results showed that CzPy was stable under ambient conditions with a blue-light emission (461 nm). Additionally, its electroluminescence properties were characterized with four different devices. Results indicated a maximum luminous efficiency reached 1.56 cd/A and maximum luminance up to 3526 cd/m2 at 10 V with commission international De L' Eclairage coordinates of (0.20, 0.24) when it was used as emitter. Furthermore, CzPy also indicated hole-transporting ability.

A three-dimensional highly stable Zn(II) coordination polymer based on 1,4-benzeneditetrazolate (H2BDT): Synthesis, crystal structure, and luminescent properties

1,4-benzeneditetrazolate [H 2 BDT] ( 1 ) and its 3D coordination polymer [Zn(BDT)] n ( 2 ), have been synthesized and structurally characterized by infrared spectroscopy (IR), thermal gravimetric analysis (TG), and single-crystal/powder X-ray diffraction. The result of the single-crystal X-ray diffraction analysis indicates that 1 is a 3D supramolecular structure stabilized by intermolecular hydrogen bonds and π…π stacking interactions. 2 is a 3D (4,4)-connected coordination polymer with the central metal Zn(II) ions linked together by BDT 2− anions. Photoluminescent measurement for 2 in the solid state elucidates that 2 displays a strong photoluminescence at 469 nm, which suggests that 2 may be a potential blue-light material. 1,4-benzeneditetrazolate [H 2 BDT] ( 1 ) and a novel 3D coordination polymer [Zn(BDT)] n ( 2 ) based on H 2 BDT, have been synthesized and structurally characterized. The result of the X-ray diffraction indicates that 1 is a 3D supramolecular structure, and 2 is a 3D (4,4)-connected coordination polymer. 2 shows high thermal stability with the decomposed temperature over 400 °C, and displays a strong photoluminescence at 469 nm at room temperature, suggesting that 2 may be a potential blue-light material. ►Anion-tuning afforded two different compounds (1, 2). ►2 showed highly thermal stability with the decomposed temperature over 400 °C. ►2 may be a potential blue-light material.

Theoretical investigation on the structure and electronic properties of Alq 2R (R = 8-hydroxyquinoline, OH, phenolate and phenylphenolate) and its derivatives

The structure and electronic properties of 5- and 6-coordinated Al complexes Alq 2R (6-coordinated Al complexes: R = q(8-hydroxyquinoline); 5-coordinated Al complexes: R = OH, P (phenolate) and B (phenylphenolate)) were investigated theoretically by means of quantum mechanical calculations based on density functional theory (DFT) and time-dependent DFT (TD-DFT) using the B3LYP functional. Geometry optimizations of the complexes were performed for the ground state (S 0) and the lowest exited stated (S 1, calculated using the configuration interaction singles (CIS) method). The second ligand (R) of 5-coordinated Al complexes is found to be important contributors in the geometry structure and the charge transport properties of the complexes. In addition, the second ligands substitutes in 5-coordinated Al complexes also noticeable affect the vertical ionizations ( VIPs), which will be expected to be used as selective hole-block materials to increase the efficiency and lifetime of the OLED. The nature and the energy of the first singlet-singlet electronic transitions have been obtained from TD-DFT, and radiative lifetimes were calculated as well. As for tuning the spectra properties, it is indicated that the electron-withdrawing methyl at 4-position of quinoline in either 5- or 6-coordinated Al complexes would be more efficient to get blue-light materials, and could obviously affect the radiative lifetimes.