Theoretical Design Study on Photophysical Properties of Light-emitting Pyrido[3,4-b]pyrazine-based Oligomers

2012 ◽  
Vol 65 (2) ◽  
pp. 169 ◽  
Author(s):  
Yanling Wang ◽  
Qiang Peng ◽  
Ping He ◽  
Zaifang Li ◽  
Ying Liang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Photophysical Properties ◽  
Charge Injection ◽  
Reorganization Energy ◽  
Theory Approach ◽  
Structure Property ◽  
Functional Theory ◽  
Light Emitting ◽  
Homo Lumo

The electronic structures, charge injection and transport, and absorption and emission properties of four series of dimethylpyrido[3,4-b]pyrazine-based oligomers (5-(5,5-dimethyl-5H-dibenzo[b,d]silol-3-yl)-2,3-dimethylpyrido[3,4-b]pyrazine)n (SPP)n, (5-(dibenzo[b,d]thiophen-3-yl)-2,3-dimethylpyrido[3,4-b]pyrazine)n (TPP)n, (5-(9,9-dimethyl-9H-fluoren-2-yl)-2,3-dimethylpyrido[3,4-b]pyrazine)n (FPP)n, (2-(2,3-dimethylpyrido[3,4-b]pyrazin-5-yl)-9-methyl-9H-carbazole)n (PPC)n were investigated by the density functional theory approach. The ground-state geometries of (SPP)n, (TPP)n, (FPP)n and (PPC)n (n = 1–4) were optimized at the B3LYP/6–31G(d) level. The energies of the HOMO, LUMO and HOMO–LUMO energy gaps of (SPP)n, (TPP)n, (FPP)n and (PPC)n (n = 1–4) were obtained by a linear extrapolation method. Further, calculations of ionization potential, electronic affinity and reorganization energy were used to evaluate charge injection and transport abilities. For (SPP)n, (TPP)n, (FPP)n and (PPC)n (n = 1–4), the time-dependent density functional theory (TDDFT) calculation results revealed that the absorption peaks can be characterized as π–π* transitions and are coupled with the location of electron density distribution change in different repeat units. All the primary theoretical investigations are intended to establish structure–property relationships, which can provide guidance in designing and preparing novel efficient organic light-emitting materials with a high performance.

Theoretical perspective on electronic structure and photophysical properties for three cyclometalated iridium(III) complexes bearing different substituent groups on the main ligands

2018 ◽  
Vol 96 (1) ◽  
pp. 18-23
Author(s):  
Deming Han ◽  
Chaoyu Wang ◽  
Shijie Fu ◽  
Jingmei Li ◽  
Shuhui Lv ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Photophysical Properties ◽  
Theoretical Perspective ◽  
Reorganization Energy ◽  
Functional Theory ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
The Density Functional Theory ◽  
Energy Emissions

To investigate the influence of the different substituents in the main ligands on the electronic structures, phosphorescent properties, and organic light-emitting devices (OLEDs) performance, three iridium(III) complexes 1, 2, and 3 are studied by means of the density functional theory/time-dependent density functional theory (DFT/TDDFT). Ionization potential, electron affinities, and reorganization energy have also been obtained to evaluate the charge transfer and balance properties between hole and electron for the three complexes. The lowest energy absorption wavelength calculated for complex 1 is in very good agreement with the experimental value. The lowest energy emissions of complexes 1, 2, and 3 are localised at 492, 565, and 510 nm, respectively, at M052X level. It is expected that this work might provide a way to develop potential iridium(III) phosphors with good electroluminescent performance.

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.

scholarly journals Single excitation energies obtained from the ensemble HOMO-LUMO gap: exact results and approximations

2022 ◽  
Author(s):  
Tim Gould ◽  
Zahed Hashimi ◽  
Leeor Kronik ◽  
Stephen Dale
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Ad Hoc ◽  
Low Cost ◽  
Theory Approach ◽  
Excitation Energies ◽  
Functional Theory ◽  
Molecular Excitation ◽  
Robust Prediction ◽  
Homo Lumo

In calculations based on density functional theory, the "HOMO-LUMO gap" (difference between the highest occupied and lowest unoccupied molecular orbital energies) is often used as a low-cost, ad hoc approximation for the lowest excitation energy. Here we show that a simple correction based on rigorous ensemble density functional theory makes the HOMO-LUMO gap exact, in principle, and significantly more accurate, in practice. The introduced perturbative ensemble density functional theory approach predicts different and useful values for singlet-singlet and singlet-triplet excitations, using semi-local and hybrid approximations. Excitation energies are of similar quality to time-dependent density functional theory, especially at high fractions of exact exchange. It therefore offers an easy-to-implement and low-cost route to robust prediction of molecular excitation energies.

scholarly journals Tuning the optoelectronic properties of hematite with rhodium doping for photoelectrochemical water splitting using density functional theory approach

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Abdur Rauf ◽  
Muhammad Adil ◽  
Shabeer Ahmad Mian ◽  
Gul Rahman ◽  
Ejaz Ahmed ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
Optical Absorption ◽  
Water Splitting ◽  
Density Functional ◽  
Formation Energy ◽  
Visible Region ◽  
Photoelectrochemical Water Splitting ◽  
Theory Approach ◽  
Functional Theory

AbstractHematite (Fe2O3) is one of the best candidates for photoelectrochemical water splitting due to its abundance and suitable bandgap. However, its efficiency is mostly impeded due to the intrinsically low conductivity and poor light absorption. In this study, we targeted this intrinsic behavior to investigate the thermodynamic stability, photoconductivity and optical properties of rhodium doped hematite using density functional theory. The calculated formation energy of pristine and rhodium doped hematite was − 4.47 eV and − 5.34 eV respectively, suggesting that the doped material is thermodynamically more stable. The DFT results established that the bandgap of doped hematite narrowed down to the lower edge (1.61 eV) in the visible region which enhanced the optical absorption and photoconductivity of the material. Moreover, doped hematite has the ability to absorb a broad spectrum (250–800) nm. The enhanced optical absorption boosted the photocurrent and incident photon to current efficiency. The calculated results also showed that the incorporation of rhodium in hematite induced a redshift in optical properties.

Photophysical Properties of N-Methyl and N-Acetyl Substituted Alloxazine: A Theoretical Investigation

2021 ◽  
Author(s):  
Huimin Guo ◽  
Xiaolin Ma ◽  
Zhiwen Lei ◽  
Yang Qiu ◽  
Bernhard Dick ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Theoretical Investigation ◽  
Density Functional ◽  
Photophysical Properties ◽  
Time Dependent ◽  
Functional Theory ◽  
Td Dft ◽  
Dependent Density

The electronic structure and photophysical properties of a series of N-Methyl and N-Acetyl substituted alloxazine (AZs) were investigated with extensive density functional theory (DFT) and time-dependent density functional theory (TD-DFT)...

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