Vibration Correlation Function Investigation on the Phosphorescence Quantum Efficiency and Spectrum for Blue Phosphorescent Ir(III) Complex

史清华,; 彭谦,; 孙少瑞,; 帅志刚,

doi:10.6023/a13010113

Cited by 11 publications

(6 citation statements)

References 10 publications

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“…Thereby, the phosphorescence quantum yield was predicted to be 92.7%, which lies within the experimentally measured range of 90–96% in different solutions at room temperature. The overall agreement demonstrates the predictive power of the present model and approach for OLED materials based on DFT/TDDFT-evaluated quantities …”

Section: Quantitative Prediction Of Light-emitting Efficiencysupporting

confidence: 63%

Computational Evaluation of Optoelectronic Properties for Organic/Carbon Materials

et al. 2014

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CONSPECTUS: Organic optoelectronic materials are used in a variety of devices, including light-emitting diodes, field-effect transistors, photovoltaics, thermoelectrics, spintronics, and chemico- and biosensors. The processes that determine the intrinsic optoelectronic properties occur either in the photoexcited states or within the electron-pumped charged species, and computations that predict these optical and electrical properties would help researchers design new materials. In this Account, we describe recent advances in related density functional theory (DFT) methods and present case studies that examine the efficiency of light emission, carrier mobility, and thermoelectric figures of merit by calculation of the electron-vibration couplings. First we present a unified vibrational correlation function formalism to evaluate the excited-state radiative decay rate constant kr, the nonradiative decay rate constant knr, the intersystem crossing rate constant kISC, and the optical spectra. The molecular parameters that appear in the formalism, such as the electronic excited-state energy, vibrational modes, and vibronic couplings, require extensive DFT calculations. We used experiments for anthracene at both low and ambient temperatures to benchmark the calculated photophysical parameters. In the framework of Fermi's golden rule, we incorporated the non-adiabatic coupling and the spin-orbit coupling to evaluate the phosphorescence efficiency and emission spectrum. Both of these are in good agreement with experimental results for anthracene and iridium compounds. Band electron scattering and relaxation processes within Boltzmann theory can describe charge transport in two-dimensional carbon materials and closely packed organic solids. For simplicity, we considered only the acoustic phonon scattering as modeled by the deformation potential approximation coupled with extensive DFT calculations for band structures. We then related the carrier mobility to the band-edge shift associated with the lattice dilation of longitudinal waves. The calculated relaxation time was in good agreement with experimental data for the graphene sheet, which supports the methodology. We then found that the intrinsic electron mobility for a 6,6,12-graphyne sheet can be even larger than that of graphene. We extended this approach to investigate the thermoelectric transport of electrons in metal phthalocyanines, which showed reasonable Seebeck coefficients when compared with experiments. For the thermal lattice transport, we employed nonequilibrium molecular dynamics simulations. Combining both electron transport and lattice thermal conductivity, we can evaluate the thermoelectric figure of merit.

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Section: Quantitative Prediction Of Light-emitting Efficiencysupporting

confidence: 63%

Computational Evaluation of Optoelectronic Properties for Organic/Carbon Materials

et al. 2014

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“…In fact, we find that this is closely related to remarkable reorganization energy: for some rigid phosphorescent molecules with small reorganization energy, the Duschinsky rotation does not play any appreciable role for both radiative and nonradiative decay rates. 63,64 As explained before, the IC rate depends on the normal mode overlap, which can only occur for the same mode if there is origin displacement. Once DRE is considered, the overlap can spread out to occur for different mode.…”

Section: Resultsmentioning

confidence: 89%

Aggregation Effects on the Optical Emission of 1,1,2,3,4,5-Hexaphenylsilole (HPS): A QM/MM Study

et al. 2014

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We investigate the photophysical property for 1,1,2,3,4,5-hexaphenylsilole (HPS) through combined quantum mechanical and molecular mechanical (QM/MM) simulations. Under the displaced harmonic oscillator approximation with consideration of the Duschinsky rotation effect (DRE), the radiative and nonradiative rates of the excited-state decay processes for HPS are calculated by using the analytical vibration correlation function approach coupled with first-principles calculations. The intermolecular packing effect is incorporated through electrostatic interaction modeled by a force field. We find that from the gas phase to the solid state (i) the side phenyl ring at the 5-position becomes coplanar with the central silacycle, which increases the degree of conjugation, thus accelerating the radiative decay process, and (ii) the rotation of the side phenyl ring at the 2-position is restricted, which blocks the excited-state nonradiative decay channels. Such a synergetic effect largely enhances the solid-state luminescence quantum efficiency through reducing the nonradiative decay rate by about 4 orders of magnitude, leading to the radiative decay overwhelming the nonradiatvie decay. In addition, the calculated solid-phase absorption and emission optical spectra of HPS are found to be in agreement with the experiment.

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“…These TVCFs have been solved analytically by multidimensional Gaussian integrations. Both the methodology and application of this formalism can be found in our previous work. − …”

Section: Methodsmentioning

confidence: 99%

Solvent Effects on the Optical Spectra and Excited-State Decay of Triphenylamine-thiadiazole with Hybridized Local Excitation and Intramolecular Charge Transfer

Fan

et al. 2014

J. Phys. Chem. A

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The triphenylamine-thiadiazole molecule (TPA-NZP) is a newly popular, highly efficient OLED fluorescent emitter with exciton utilization efficiency exceeding the upper limit of spin statistics (25%). In this work, the optical spectra and the radiative and nonradiative decay rate constants have been investigated theoretically for TPA-NZP in hexane, ethyl ether, tetrahydrofuran, and dimethylformamide solvents, in comparison with the gas phase. We observed the evolutions of the excited states from the hybridized local and charge-transfer (HLCT) character to complete intramolecular charge transfer (CT) character with the increase of the solvent polarities. It is found that upon increasing the solvent polarity, the amount of red shift in the absorption peak is much less than that of emission, resulting in breakdown of the mirror symmetry. This is because that 0-0 transition energy is red-shifted but the vibrational relaxation increases with the solvent polarity, leading to subtraction in absorption while addition in emission. The radiative decay rate constant is calculated to be almost independent of polarity. The nonradiative decay rate increases by almost one order of magnitude from that in nonpolar hexane to the strongly polarized dimethylformamide, which is attributed to the dual effects of the red shift in the gap and enhancement of the vibrational relaxation by solvent polarity.

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Vibration Correlation Function Investigation on the Phosphorescence Quantum Efficiency and Spectrum for Blue Phosphorescent Ir(III) Complex

Cited by 11 publications

References 10 publications

Computational Evaluation of Optoelectronic Properties for Organic/Carbon Materials

Computational Evaluation of Optoelectronic Properties for Organic/Carbon Materials

Aggregation Effects on the Optical Emission of 1,1,2,3,4,5-Hexaphenylsilole (HPS): A QM/MM Study

Solvent Effects on the Optical Spectra and Excited-State Decay of Triphenylamine-thiadiazole with Hybridized Local Excitation and Intramolecular Charge Transfer

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