Analysis of hole transport in a polyfluorene-based copolymer— evidence for the absence of correlated disorder

Vries, de Rj Rein; Mensfoort, van Slm Siebe; Shabro, V; Vulto, Sie; Janssen, Raj René; Coehoorn, R.

doi:10.1063/1.3119317

Cited by 38 publications

(34 citation statements)

References 18 publications

(19 reference statements)

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“…[ 43 ] Steady-state SCLC diode measurements of fl uorene-triarylamine copolymers have also been successfully fi tted to the correlated and uncorrelated EGDM. [ 44 ] The EGDM with correlated disorder (ECDM) does predict a mobility which is fi eld dependent and charge-carrier independent (we note that analysis of the experimentally measured transport parameters for PFB and PFMO within the ECDM framework (see Supporting Information, Section S10) does, assuming an interchain hopping distance of 1 nm and a hopping attempt frequency of 10 14 s −1 , yield not unreasonable values for the wavefunction decay length of 0.14-0.29 nm, respectively). The EMA theory with correlated disorder also predicts a mobility which is fi eld dependent and effectively charge-carrier independent at the DOS widths found for PFB and PFMO.…”

Section: Resultsmentioning

confidence: 99%

“…[ 43 ] More recently they have also been used to test the correlated and uncorrelated EGDM in the low charge-carrier density regime using steady-state SCLC diode measurements. [ 44 ] Here we investigate the charge-density dependence of the hole mobility across both the low and high charge-carrier density regimes in two fl uorene-triarylamine copolymers, poly(9,9-dioctylfl uorene-co -bis-N,N ′-(4-butylphenyl)-bis-N,N ′-phenyl-1,4-phenylenediamine) (PFB) and poly(9,9-dioctylfluorene-co -bis-N,N ′-(4-methoxyphenyl)-bis-N,N ′-phenyl-1,4-phenylenediamine) (PFMO). These have been chosen due to their low ionization potentials to minimize the impact of any charge injection effects on the measured mobility values.…”

Section: Introductionmentioning

confidence: 99%

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Charge‐Carrier Density Independent Mobility in Amorphous Fluorene‐Triarylamine Copolymers

Campbell

Rawcliffe

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et al. 2016

Adv Funct Materials

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3720 wileyonlinelibrary.com (OPVs), and organic fi eld-effect transistors (OFETs). A crucial parameter in the development of these technologies is the OSC charge-carrier mobility, and how it is related to the different OSC materials, processing, device architectures, and device operating conditions. Many semiconducting polymers and small molecules are amorphous, and such disorder in the physical morphology is expected to refl ect itself in disorder of the energy levels of the hole and electron transport states ( Figure 1 a). Such energetic disorder will directly impact charge transport and mobility. [1][2][3][4][5][6][7][8][9][10][11][12] For such energetically disordered OSCs, one feature predicted by many charge transport models is a charge-carrier density dependent mobility. The original Gaussian disorder model (GDM) developed by Bässler for hopping transport in a Gaussian density of states (DOS) distribution was a single carrier approach, [ 1 ] as were the models based on it which considered both correlated energetic disorder, [ 2 ] with a smoothly varying energy landscape (see Figure 1 a), and the effect of polaronic relaxation. [ 3 ] The percolation model developed by Vissenberg and Matters for transport involving an exponential DOS instead considered multiple carriers, [ 4 ] and this predicted a mobility which has a power-law dependency on the charge-carrier density. The measured transistor mobility falls two to three orders of magnitude below that predicted from the charge-carrier density dependent model, and does not follow the expected power-law relationship. The experimental results for these two amorphous polymers are therefore consistent with a charge-carrier density independent mobility, and this is discussed in terms of polaron-dominated hopping and interchain correlated disorder.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Charge‐Carrier Density Independent Mobility in Amorphous Fluorene‐Triarylamine Copolymers

Campbell

Rawcliffe

Guite

et al. 2016

Adv Funct Materials

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“…A comparison of EGDM and ECDM modeling of current-voltage characteristics of hole-only devices of conjugated polymers such as derivatives of PPV 10 and a polyfluorene-based copolymer 11 has led to the conclusion that for these polymers the intersite distance as obtained from a fit of the EGDM modeling is more realistic than the one obtained from a fit of the ECDM modeling. On the other hand, a similar comparison of EGDM and ECDM modeling of current-voltage characteristics of hole-only devices of the molecule N,N -bis(1-naphthyl)-N,N -diphenyl-1,1 -biphenyl-4,4 -diamine (α-NPD) and of electron-only devices of the molecule bis(2-methyl-8-quinolinolato)(4-phenylphenolato) aluminum (BAlq) shows that the intersite distance as obtained from a fit with the ECDM modeling is more realistic than the one obtained with the EGDM modeling.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo study of charge transport in organic sandwich-type single-carrier devices: Effects of Coulomb interactions

et al. 2011

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“…[18][19][20] We have recently performed modeling studies of current-voltage characteristics of hole-only devices of a derivative of PPV ͑Ref. 21͒ and of a polyfluorene-based copolymer, 22 both with spatially uncorrelated and correlated Gaussian disorder. These models are commonly called the Gaussian disorder model ͑GDM͒ and the correlated disorder model, respectively.…”

Section: Introductionmentioning

confidence: 99%

Electron-hole recombination in disordered organic semiconductors: Validity of the Langevin formula

et al. 2009

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Accurate modeling of electron-hole recombination in organic light-emitting diodes ͑OLEDs͒ is essential for developing a complete description of their functioning. Traditionally, the recombination rate is described by the Langevin formula, with a proportionality factor equal to the sum of the electron and hole mobilities. In the disordered organic semiconductors used in OLEDs these mobilities have been shown to depend strongly on the carrier densities and on the electric field. Moreover, the energetic disorder leads to percolating pathways for the electron and hole currents, which may or may not be correlated. To answer the question whether the Langevin formula is still valid under such circumstances we perform Monte Carlo simulations of the recombination rate for Gaussian energetic disorder. We vary the disorder energy, the temperature, the densities, and mobility ratio of electrons and holes, the electric field, and the type of correlation between the electron and hole energies. We find that at zero electric field the Langevin formula is surprisingly well obeyed, provided that a change in the charge-carrier mobilities due to the presence of charge carriers of the opposite type is taken into account. Deviations from the Langevin formula at finite electric field are small at the field scale relevant for OLED modeling.

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Analysis of hole transport in a polyfluorene-based copolymer— evidence for the absence of correlated disorder

Abstract: van Mensfoort, S.L.M.; Shabro, V.; Vulto, S.I.E.; Janssen, R.A.J.; Coehoorn, R.

Cited by 38 publications

References 18 publications

Charge‐Carrier Density Independent Mobility in Amorphous Fluorene‐Triarylamine Copolymers

Charge‐Carrier Density Independent Mobility in Amorphous Fluorene‐Triarylamine Copolymers

Monte Carlo study of charge transport in organic sandwich-type single-carrier devices: Effects of Coulomb interactions

Electron-hole recombination in disordered organic semiconductors: Validity of the Langevin formula

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