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

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.

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.

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.

scholarly journals Do two oxidants (ferric-peroxo and ferryl-oxo species) act in the biosynthesis of estrogens? A DFT calculation

RSC Advances ◽  
2018 ◽  
Vol 8 (27) ◽  
pp. 15196-15201 ◽  
Author(s):  
Xiang-Yun Wang ◽  
Hui-Min Yan ◽  
Yan-Li Han ◽  
Zhu-Xia Zhang ◽  
Xiao-Yun Zhang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Dft Calculation ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Two Oxidants ◽  
Ferric Peroxo

Density functional theory calculations were performed in order to reveal the mysterious catalytic step of the biosynthesis of estrogens.

Spin Alignment Studies on the Muon-Site Determination in La2CuO4

2020 ◽  
Vol 860 ◽  
pp. 154-159
Author(s):  
Muhammad Redo Ramadhan ◽  
Irwan Ramli ◽  
Dita Puspita Sari ◽  
Budhy Kurniawan ◽  
Azwar Manaf ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Potential Distribution ◽  
Density Functional ◽  
Dft Calculation ◽  
Minimum Energy ◽  
Point Dipole ◽  
Spin Alignment ◽  
Functional Theory ◽  
Muon Site ◽  
Insulating Gap

Here we report spin-alignment contributions to muon coordinate calculated utilizing density functional theory (DFT) calculation. We estimated four different antiferromagnetic (AF) spin alignments in La2CuO4. We observed small changes by adjusting spin configurations in DFT calculations. Cu-spin value of 0.61 µB is constant in all calculations. The insulating gap of 1.9 eV is unchanged in all configurations. Muon coordinate was defined as the most minimum energy in atomic potential distribution. By assuming that Cu-spin is a point dipole for each atom, internal fields for muon were calculated and compared to known experimental results.

Sign in / Sign up

Export Citation Format

Share Document