Theoretical Studies of the Absorption and Emission Properties of the Fluorene-Based Conjugated Polymers

Wang, Jifen; Feng, Jing; Ren, Ai‐Min; Liu, Xiaodong; Ma, Yan; Lü, Ping; Zhang, Hongxing

doi:10.1021/ma035725c

Cited by 93 publications

(112 citation statements)

References 32 publications

(80 reference statements)

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“…Because longer oligomers of well-defined chain length (n > 6) were not available until the mid 1990s, [29] the linear dependence prevailing for mediumsize oligomers stimulated a large number of research groups to extrapolate the oligomer values to the limit of an ideal infinite conjugated polymer chain by linear regression. [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] However, the experimental optical bandgaps of oligomers with n > 6 [45][46][47][48] were always significantly larger than the extrapolated values. This became more and more evident with the growing length of soluble oligomers.…”

Section: Extrapolation Procedures To the Polymer Limitmentioning

confidence: 99%

Optical Bandgaps of π‐Conjugated Organic Materials at the Polymer Limit: Experiment and Theory

2007

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In this Review, the extreme care that must be taken when predicting the optical properties of conjugated polymers via the oligomer approach, and when comparing theoretical and experimental data, is illustrated. In the first part, conceptual strategies for the correct determination of optical transitions from experimental spectra and relevant extrapolation procedures at the polymer limit are introduced. The impact of conformational, substitution, solvent, and solid‐state effects on the optical properties is discussed in light of experimental data reported for molecular backbones based on phenylene, phenylenevinylene, and thiophene repeat units. A comparison is then made between experimental results and those provided by standard quantum‐chemical methods, to assess their reliability.

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Section: Extrapolation Procedures To the Polymer Limitmentioning

confidence: 99%

Optical Bandgaps of π‐Conjugated Organic Materials at the Polymer Limit: Experiment and Theory

2007

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“…It has been increasingly used in investigating the optical properties of compounds. 37,38 And in Figure 4, we can see the linear relationship among the calculated Δ H-L or E g and the inverse chain length. There is a good linear relation between the energy gaps by two methods and the inverse chain length.…”

Section: Homo-lumo Gaps and The Lowest Excitation Energiesmentioning

confidence: 88%

Theoretical Studies on the Electronic and Optical Properties of a New Class of Aromatic Oligomers and Polymers

Feng

Ren

et al. 2008

Chin. J. Chem.

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The purpose of this work is to provide an in-depth interpretation of the optical and electronic properties of a series of aromatic oligomers and polymers, including [N-(4-(5-(3-(1,3,4-oxadiazol-2,5-ylene). These polymers and oligomers show great potential for application to organic light-emitting diodes (OLEDs) as efficient blue emitters due to the tuning of the optical and electronic properties. The geometric and electronic structures of the oligomers in the ground state were investigated using density functional theory (DFT) and the ab initio HF, whereas the lowest singlet excited state of NPPP 1 was optimized with ab initio configuration interaction singles (CIS). To assign the absorption and emission peaks observed in the experiment, the absorption and emission spectra of the ground and lowest singlet excited states were calculated with time-dependent DFT (TD-DFT) and Zerner's independent neglect of differential overlap (ZINDO). All DFT calculations were performed using the B3LYP functional and the 6-31G basis set. The results show that the HOMO, LUMO, energy gaps, ionization potentials, and electron affinities for these polymers are affected by increasing the conjugated chain, which favors the hole and electron injection into OLED. The trend of the variation of Δ H-L and the lowest excitation energies with 1/n, and the electronic structure and optical properties of these polymers were extrapolated and analyzed. The absorption spectra exhibit red shifts to some extent [the absorption spectra: 359.

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“…Their electronic structures have been extensively studied [20,21,22,23,24]. We employed the oligomer of fluorene (oligo-FL) with n = 8 and carried out the MEM calculation.…”

Section: Fluorenementioning

confidence: 99%

Improved Maximum Entropy Method applied to Real-time Time-Dependent Density Functional Theory

Toogoshi

Kano

Zempo

2017

J. Phys.: Conf. Ser.

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Abstract.The maximum entropy method (MEM) is one of the key techniques for spectral analysis. The main feature is to describe spectra in low frequency with short time-series data. We adopted MEM to analyze the spectrum from the dipole moment obtained by the timedependent density functional theory (TDDFT) calculation in real time, which is intensively studied and applied to computing optical properties. In the MEM analysis, we proposed that we use the concatenated data set made from several-times repeated raw data together with the phase. We have applied this technique to spectral analysis of the TDDFT dipole moment of oligo-fluorene with n = 8. As a result, the higher resolution can be obtained without any peak shift due to the phase jump. The peak position is in good agreement to that of FT with just raw data. This paper presents the efficiency and characteristic features of this technique. IntroductionTime-dependent density functional theory (TDDFT) is a powerful tool for analyzing optical properties of medium-to-large sized molecule. We employ a real-time and real-space technique to solve the time-dependent Kohn-Sham equations. Within the framework of this approach, the wave functions are calculated by the finite difference method on real spatial grids [1] without using explicit bases such as plane waves or Gaussian. In our procedure to calculate optical properties, we use the time-series data, namely the dynamic dipole moment, from whose Fourier transform (FT) optical properties are calculated in a usual technique. The spectral resolution depends on the length of the dipole moment. To obtain the good resolution, the computational cost is quite expensive.To solve this difficulty, we focus on Maximum Entropy Method (MEM) [2], which is one of the key techniques of spectrum analysis. The principles of MEM are methods of the information theory for estimating unknown probability distributions based on the information about their expected values. MEM is widely used to the solution of a variety of problems related to spectral estimation such as earth and planetary science [3], spectroscopy [4]. The main feature is to obtain a fairy high resolution and accuracy with a relatively small number of time-series data. MEM is based on the Fourier pair of the autocorrelation and power spectrum. We applied this technique to spectral analysis of time-dependent dipole moments of molecules, which is calculated by realtime TDDFT. In the comparison of MEM and FT spectrum for several molecules, we realize that MEM needs less time step than FT to obtain the optical spectrum with same resolution [6]. As a new improved MEM, we proposed to use the concatenated data set made from several-times

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Theoretical Studies of the Absorption and Emission Properties of the Fluorene-Based Conjugated Polymers

Cited by 93 publications

References 32 publications

Optical Bandgaps of π‐Conjugated Organic Materials at the Polymer Limit: Experiment and Theory

Optical Bandgaps of π‐Conjugated Organic Materials at the Polymer Limit: Experiment and Theory

Theoretical Studies on the Electronic and Optical Properties of a New Class of Aromatic Oligomers and Polymers

Improved Maximum Entropy Method applied to Real-time Time-Dependent Density Functional Theory

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