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101.
Deep‐Blue Phosphorescent Ir(III) Complexes with Light‐Harvesting Functional Moieties for Efficient Blue and White PhOLEDs in Solution‐Process 下载免费PDF全文
Ganguri Sarada Woosum Cho Athithan Maheshwaran Vijaya Gopalan Sree Ho‐Yeol Park Yeong‐Soon Gal Myungkwan Song Sung‐Ho Jin 《Advanced functional materials》2017,27(27)
The photoluminescence (PL) efficiency of emitters is a key parameter to accomplish high electroluminescent performance in phosphorescent organic light‐emitting diodes (PhOLEDs). With the aim of enhancing the PL efficiency, this study designs deep‐blue emitting heteroleptic Ir(III) complexes (tBuCN‐FIrpic, tBuCN‐FIrpic‐OXD, and tBuCN‐FIrpic‐mCP) for solution‐processed PhOLEDs by covalently attaching the light‐harvesting functional moieties (mCP‐Me or OXD‐Me) to the control Ir(III) complex, tBuCN‐FIrpic. These Ir(III) complexes show similar deep‐blue emission peaks around 453, 480 nm (298 K) and 447, 477 nm (77 K) in chloroform. tBuCN‐FIrpic‐mCP demonstrates higher light‐harvesting efficiency (142%) than tBuCN‐FIrpic‐OXD (112%), relative to that of tBuCN‐FIrpic (100%), due to an efficient intramolecular energy transfer from the mCP group to the Ir(III) complex. Accordingly, the monochromatic PhOLEDs of tBuCN‐FIrpic‐mCP show higher external quantum efficiency (EQE) of 18.2% with one of the best blue coordinates (0.14, 0.18) in solution‐processing technology. Additionally, the two‐component (deep‐blue:yellow‐orange), single emitting layer, white PhOLED of tBuCN‐FIrpic‐mCP shows a maximum EQE of 20.6% and superior color quality (color rendering index (CRI) = 78, Commission Internationale de L'Eclairage (CIE) coordinates of (0.353, 0.352)) compared with the control device containing sky‐blue:yellow‐orange emitters (CRI = 60, CIE coordinates of (0.293, 0.395)) due to the good spectral coverage by the deep‐blue emitter. 相似文献
102.
103.
The effects of pyrite (FeS2) and pyrrhotite (Fe7S8) on free radical formation in a coal sample (81% carbon content) have been investigated by electron spin resonance (e.s.r.) spectroscopy. Changes in the e.s.r. parameters (spin concentration g-1, n, linewidth ΔH and g-value) were monitored in samples of coal, coal+8% FeS2 and coal+8% Fe7S8, as these samples were heated in vacuum or in hydrogen from room temperature to 500 °C, in steps of 50 °C for a residence time of 30 min at each temperature. In vacuum heating, changes in n begin to occur at 400 °C, 350 °C and 300 °C respectively for coal, coal+8%Fe7S8 and coal+8% FeS2 samples whereas in H2, the corresponding temperatures are 250 °C, 200 °C and 150 °C. Changes in ΔH and g were also observed at these temperatures. The maximum increase in n occured for coal+8% FeS2 samples whereas the minimum increase was observed for the pure coal sample. It is argued that enhancement in n is due to two mechanisms: the pyrite to pyrrhotite conversion and the presence of pyrrhotite itself. The detailed nature of the catalytic activity of pyrrhotite is not known. 相似文献
104.
A new composite film was prepared by depositing hydrous ruthenium oxide (RuO2) particles into a polymer matrix comprising of poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(styrene sulfonic acid) (PSS). The composite, PEDOT-PSS-RuO2, showed an enhanced capacitance and optical properties due to the presence of RuO2 particles in the composite. Specific capacitance of the PEDOT-PSS-RuO2 composite was found to be 1409 F/g. After anodic polarization, the PEDOT-PSS-RuO2 composite film exhibited enhanced visible-light coloration in comparison with PEDOT/PSS and simple RuO2 films. Differential voltabsorptometric curves (dA/dt versus potential (derivative cyclic voltabsorptogram, DCVA)) were deduced for few selected wavelengths to characterize the optical properties. The changes in the electrochromic characteristics (in the visible region) of the composite is attributed mainly to transition of Ru(III) to Ru(IV). SEM images revealed the presence of smaller sized particles of hydrous ruthenium oxide in the composite film. The existence of smaller size RuO2 particles having more active surface area is the reason for the enhanced capacitance and optical properties. 相似文献
105.
Hydrous RuO2 particles were electrochemically loaded into poly(3,4-ethylenedioxythiophene) doped poly(styrene sulfonic acid), PEDOT-PSS, matrix by employing various potential cycles in cyclic voltammetry and to fabricate the PEDOT-PSS-RuO2·xH2O electrode. The amount of hydrous RuO2 particles loaded into the PEDOT-PSS matrix was easily controlled by varying the number of potential cycles. Scanning electron microscopy photographs reveal a uniform dispersion of hydrous RuO2 particles in the porous structure of PEDOT-PSS matrix. Raman spectrum confirms the incorporation of hydrous RuO2 into PEDOT-PSS matrix. Chronopotentiometry and cyclic voltammetry were employed in 0.5 M H2SO4 to evaluate the capacitor properties. Specific capacitance values were determined by chronoamperometry. An increasing trend in specific capacitance with loaded amount of hydrous RuO2 particles in PEDOT-PSS was noticed. A maximum specific capacitance of 653 F/g was achieved. 相似文献
106.
Siddaramaiah T. Jeevananda K. S. Jagadeesh H. Somashekarappa R. Somashekar 《应用聚合物科学杂志》2003,90(11):2938-2944
Linear low‐density polyethylene (LLDPE) with different fillers such as silica, mica, and soy protein isolate were compounded using a single screw extruder and blown into films by a Konark blow‐film machine. The filled LLDPE films were characterized for physicomechanical and optical properties. Barrier properties such as water vapor transmission rate and oxygen transmission rate of the filled LLDPE films were also reported. Microcrystalline parameters such as crystal size (〈N〉) and lattice distortion (g in %) of the filled LLDPE films were estimated from the wide‐angle X‐ray scattering method using Hosemann's paracrystalline model. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2938–2944, 2003 相似文献
107.
Curing of N,N,N′,N′‐tetraglycidyldiaminodiphenylmethane with new curing agents like 3,3′‐dichloro‐4,4′‐diaminodiphenylmethane and 2,2′‐dichloro‐4,4′‐diaminodiphenylmethane in comparison with diaminodiphenylmethane and 4,4′‐diaminodiphenylsulphone (DDS) was carried out using dynamic differential scanning calorimetry. The shelf life of various epoxy formulations was evaluated by the residual cure exotherm method. The glass‐transition temperatures of cured epoxy formulations were determined using dynamic mechanical analysis. The mechanical properties such as the tensile strength, tensile modulus, flexural strength, and Izod impact strength were also evaluated and compared. The activation energy, frequency factor, and shelf life of chloro‐substituted hardener formulations were high as compared to those of unsubstituted hardener formulations. The marginal differences in the glass‐transition temperature, tensile strength, tensile modulus, and flexural strength and the small decrement in the Izod impact strength values were interpreted in terms of chlorine substitution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3082–3088, 2002; DOI 10.1002/app.2337 相似文献
108.
Epitaxial thin films of orthorhombic KNbO3 (100)/(010) were deposited on MgO (100) single-crystal substrates by pulsed laser ablation using an ε120 Å SrTiO3 (110) transition layer in between. From X-ray diffraction, the orientation relationships were determined as (010) [100] or (100) [010] KNb03 ∥ (110) [110] SrTiO3 ∥ (100) [011] MgO and (010) [001] or (100) [001] KNbO3 ∥ (110) [001] SrTiO3 ∥ (100) [011] MgO. The measured film refractive indices at 632.8 nm were 2.213 ± 0.003, 2.278 ± 0.003, and 2.285 ± 0.003, respectively, along MgO [100], [011], and [011] directions. A model was developed to correlate the measured effective refractive indices of the film to area fractions of domain variants in the film. Using the model, the area fraction of domains with their polarization axis normal to the substrate was estimated to be 60.0 ± 2.7%. 相似文献
109.
Given a DNF formula f on n variables, the two natural size measures are the number of terms or size s(f) and the maximum width of a term w(f). It is folklore that small DNF formulas can be made narrow: if a formula has m terms, it can be ${\epsilon}$ -approximated by a formula with width ${{\rm log}(m/{\epsilon})}$ . We prove a converse, showing that narrow formulas can be sparsified. More precisely, any width w DNF irrespective of its size can be ${\epsilon}$ -approximated by a width w DNF with at most ${(w\, {\rm log}(1/{\epsilon}))^{O(w)}}$ terms. We combine our sparsification result with the work of Luby & Velickovic (1991, Algorithmica 16(4/5):415–433, 1996) to give a faster deterministic algorithm for approximately counting the number of satisfying solutions to a DNF. Given a formula on n variables with poly(n) terms, we give a deterministic ${n^{\tilde{O}({\rm log}\, {\rm log} (n))}}$ time algorithm that computes an additive ${\epsilon}$ approximation to the fraction of satisfying assignments of f for ${\epsilon = 1/{\rm poly}({\rm log}\, n)}$ . The previous best result due to Luby and Velickovic from nearly two decades ago had a run time of ${n^{{\rm exp}(O(\sqrt{{\rm log}\, {\rm log} n}))}}$ (Luby & Velickovic 1991, in Algorithmica 16(4/5):415–433, 1996). 相似文献
110.
Khuller and Schieber (1992) in [1] developed a constructive algorithm to prove that the existence of k-vertex independent trees in a k-vertex connected graph implies the existence of k-edge independent trees in a k-edge connected graph. In this paper, we show a counterexample where their algorithm fails. 相似文献