scholarly journals Eu- and Tb-adsorbed Si3N4 and Ge3N4: Tuning the colours with one luminescent host

2021 ◽  
Author(s):  
Cordula Braun ◽  
Liuda Mereacre ◽  
Zheng Chen ◽  
Adam Slabon ◽  
David Vincent ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Light Emitting Diodes ◽  
Structural Diversity ◽  
Functional Theory ◽  
Light Emitting ◽  
Lighting Industry ◽  
White Light Emitting Diodes ◽  
Display Systems

Phosphor-converted white light-emitting diodes (pc-LEDs) are emerging as an indispensable solid-state light source for the next generation lighting industry and display systems due to their unique properties. Nitrides with their wide-ranging applicability due to their intriguing structural diversity, their auspicious chemical and physical properties represent an essential component in industrial and materials applications. Here, we present the successful adsorption of Eu and Tb at the grain boundaries of bulk β-Si3N4 and β-Ge3N4 by a succeeding combustion synthesis. The adsorption of europium and terbium and the synergic combination of both resulted in intriguing luminescence properties of all compounds (red, green, orange and yellow). Especially the fact that one host can deliver different colours renders Eu,Tb-β-M3N4 (M= Si, Ge) as prospective chief components for future light emitting diodes (LEDs). For the elucidation of the RE adsorption on the electronic properties of β-Si3N4 and β-Ge3N4, Mott-Schottky (MS) measurements were conducted for the bare and RE adsorbed samples. Further insight on the electronic structure of β-Si3N4 and β-Ge3N4 were obtained via density functional theory (DFT) computations.

scholarly journals Theoretical Investigation on Electronic Structure and Photophysical Properties of a Series of Mixed-Carbene Cyclometalated Iridium(III) Complexes With Different Ancillary Ligand Applied in Phosphorescent Organic Light-Emitting Diodes

2021 ◽  
Author(s):  
Tong Chen ◽  
Deming Han ◽  
Lihui Zhao ◽  
Bao Wang ◽  
Xiaohong Shang
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Light Emitting Diodes ◽  
Photophysical Properties ◽  
Organic Light Emitting Diodes ◽  
Ancillary Ligand ◽  
Functional Theory ◽  
Light Emitting ◽  
Organic Light

Abstract By using density functional theory (DFT) and time-dependent density functional theory (TDDFT), the geometrical structure, electronic structure and photophysical properties of a series of mixed-carbene cyclometalated iridium(III) complexes with different ancillary ligand have been explored. The frontier molecular orbital (FMO) components and energy levels for all studied complexes have been investigated. The lowest lying absorptions were calculated to be at 327, 322, 333, 332 and 332 nm for these complexes, which have the transition configuration of HOMO→LUMO. The lowest energy emissions for these complexes are localized at 413, 399, 498, 418 and 415 nm, respectively, simulated in CH2Cl2 medium at the M062X level. One complex designed could possess the largest radiative decay rate (kr) value and be a potential candidate for blue emitters in organic light-emitting diodes (OLEDs). The theoretical study can provide a useful guidance for design and synthesis of new iridium(III) complexes in phosphorescent materials.

Theoretical Study of the Electronic Structure and Properties of Alternating Donor-Acceptor Couples of Carbazole-Based Compounds for Advanced Organic Light-Emitting Diodes (OLED)

2019 ◽  
Vol 824 ◽  
pp. 236-244
Author(s):  
Suppamat Makjan ◽  
Malinee Promkatkaew ◽  
Supa Hannongbua ◽  
Pornthip Boonsri
Keyword(s):  
Density Functional Theory ◽  
Electronic Properties ◽  
Density Functional ◽  
Light Emitting Diodes ◽  
Functional Theory ◽  
Light Emitting ◽  
Organic Light ◽  
Hole Transporting ◽  
Photorefractive Materials ◽  
Donor Acceptor

Generally, it is difficult to generate a high-performance pure blue emission organic light-emitting diode (OLED). That is because the intrinsically wide band-gap makes it hard to inject charges into the emitting layer in such devices. To solve the problem, carbazole derivatives have been widely used because they have more thermal stability, a good hole transporting property, more electron rich (p-type) material, and higher photoconductivity. In the present work, novel copolymers containing donor-acceptor-acceptor-donor (D-A-A-D) blue compounds used for OLEDs were investigated. The theory of the geometrical and electronic properties of N-ethylcarbazole (ECz) as donor molecule (D) coupled to a series of 6 acceptor molecules (A) for advanced OLEDs were investigated. The acceptors were thiazole (TZ), thiadiazole (TD), thienopyrazine (TPZ), thienothiadiazole (TTD), benzothiadiazole (BTD), and thiadiazolothienopyrazine (TDTP). The ground state structure of the copolymers were studied using Density Functional Theory (DFT) at B3LYP/6-31G(d) level. Molecular orbital analysis study indicated 3 investigated copolymers (ECz-diTZ-ECz, ECz-diTD-ECz, ECz-diBTD-ECz) have efficient bipolar charge transport properties for both electron and hole injection to the TiO2 conduction band (4.8 eV). In addition, the excited states electronic properties were calculated using Time-Dependent Density Functional Theory (TD-DFT) at the same level. Among these investigated copolymer ECz-diTZ-ECz and ECz-diTD-ECz showed the maximum absorption wavelengths (λabs) with blue emitting at 429 and 431 nm, respectively. The results suggested that selected D-A-A-D copolymers can improve the electron- and hole- transporting abilities of the devices. Therefore, the designed copolymers would be a promising material for future development of light-emitting diodes, electrochromic windows, photovoltaic cells, and photorefractive materials.

Luminescence and density functional theory (DFT) calculation of undoped nitridosilicate phosphors for light-emitting diodes

2012 ◽  
Vol 22 (12) ◽  
pp. 5828 ◽  
Author(s):  
Chiao-Wen Yeh ◽  
Yun-Ping Liu ◽  
Zhi Ren Xiao ◽  
Yin-Kuo Wang ◽  
Shu-Fen Hu ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Dft Calculation ◽  
Light Emitting Diodes ◽  
Functional Theory ◽  
Light Emitting

Chain Morphologies in Blue-Emitting Polyfluorenes: Impact on Light-Emitting Diodes

2006 ◽  
Vol 916 ◽  
Author(s):  
Suchi Guha ◽  
M. Arif ◽  
C. Volz
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Light Emitting Diodes ◽  
Spectral Feature ◽  
Density Functional Theory Calculations ◽  
Beta Phase ◽  
Single Chain ◽  
Functional Theory ◽  
Light Emitting ◽  
Conformational Isomers

AbstractDioctyl-substituted polyfluorene (PF) is especially well known for the presence of an unusual spectral feature identified as the beta phase, known to originate in regions of enhanced chain planarity. Although this phase appears as a minority constituent it dominates the emission, resulting in a red shift of the luminescence. We present Raman scattering studies of poly[9,9'-(di n, octyl) fluorene] as a function of thermal cycling that establish a connection between the conformational isomers and chain morphology. Density-functional theory calculations of the vibrational spectra of single chain oligomers in conjunction with our experimental results demonstrate the incompatibility of the beta phase with the overall alpha crystalline phase. Further, electroluminescence and photoluminescence measurements from PF-based light-emitting diodes are presented and discussed in terms of the crystalline phases and chain morphologies in the PFs.

Doping effects on the geometric and electronic structure of tin clusters

2019 ◽  
Vol 21 (44) ◽  
pp. 24478-24488 ◽  
Author(s):  
Martin Gleditzsch ◽  
Marc Jäger ◽  
Lukáš F. Pašteka ◽  
Armin Shayeghi ◽  
Rolf Schäfer
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Beam Deflection ◽  
Functional Theory ◽  
Doping Effects ◽  
Depth Analysis ◽  
Trajectory Simulations

In depth analysis of doping effects on the geometric and electronic structure of tin clusters via electric beam deflection, numerical trajectory simulations and density functional theory.

scholarly journals Influence of Copper(I) Halides on the Reactivity of Aliphatic Carbodiimides

2020 ◽  
Vol 3 (1) ◽  
pp. 20
Author(s):  
Valentina Ferraro ◽  
Marco Bortoluzzi
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
General Formula ◽  
Electron Density ◽  
Density Functional ◽  
Functional Theory ◽  
Fukui Functions ◽  
Bond Lengths ◽  
Linear Complexes ◽  
Nitrogen Bond

The influence of copper(I) halides CuX (X = Cl, Br, I) on the electronic structure of N,N′-diisopropylcarbodiimide (DICDI) and N,N′-dicyclohexylcarbodiimide (DCC) was investigated by means of computational DFT (density functional theory) methods. The coordination of the considered carbodiimides occurs by one of the nitrogen atoms, with the formation of linear complexes having a general formula of [CuX(carbodiimide)]. Besides varying the carbon–nitrogen bond lengths, the thermodynamically favourable interaction with Cu(I) reduces the electron density on the carbodiimides and alters the energies of the (NCN)-centred, unoccupied orbitals. A small dependence of these effects on the choice of the halide was observable. The computed Fukui functions suggested negligible interaction of Cu(I) with incoming nucleophiles, and the reactivity of carbodiimides was altered by coordination mainly because of the increased electrophilicity of the {NCN} fragments.

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