Effect of Coulomb correlation on charge transport in disordered organic semiconductors

Liu, Feilong; Eersel, Harm van; Xu, Bojian; Wilbers, Janine G. E.; Jong, M. P. de; Wiel, Wilfred G. van der; Bobbert, Peter A.; Coehoorn, R.

doi:10.1103/physrevb.96.205203

Cited by 33 publications

(39 citation statements)

References 44 publications

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“…Further progress was made in elucidating differences between ME and kMC models [119] and in addressing computational challenges of kMC methods such as parallelization, [121] explicit long-range Coulomb interaction, [122] and finite system sizes. [123] In combination, these developments resulted in a large gain in speed for modern kMC implementations.…”

Section: Mesoscalementioning

confidence: 99%

Toward Design of Novel Materials for Organic Electronics

et al. 2019

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organic/inorganic perovskites solar cells [6] to printable electronic circuits based on organic field-effect transistors (OFETs). [7] While OLED displays outperform their inorganic counterparts in terms of energy efficiency, [8] scientific and technical challenges concerning the stability and processability of the organic materials used in large-area OLEDs and organic solar cells remain. New challenges arise from applications, such as displays on flexible substrates, OLED lightning, large area displays as well as for printable or solution processable larger area solar cells. [8] Many of the remaining challenges are material related, e.g., the low mobility of charge carriers in organic materials in general and in amorphous organic semiconductors in particular. There are other materials related issues, such as limited OLED life times due to unstable blue hosts and emitters, [9] low fill factors, and therefore reduced power conversion efficiencies of organic solar cells, [10,11] low conductivity and high costs of organic charge transport layers of perovskite solar cells [6,12,13] and low conductivity and hard processability of crystalline OFET materials. [14] Conductivity and injection can be improved by doping the organic thin films with molecular dopants with high electron affinities (p-type) [15] or low ionization energies (n-type). [16] The doping mechanism of organic materials is in many cases not well understood, [17] making material and device optimization a costly experimental endeavor.The development of better materials is presently based on chemical insight, in part guided by theoretical understanding, or the experimental screening of large numbers of compounds. Given the size of the potentially available chemical space this remains a costly and time-consuming approach. Recent successes in experimental design of novel materials and concepts include the development of a stable strong molecular n-type dopant, [16] a study about the quantitative relation between interaction parameter, miscibility, and function of conjugated polymer donors and small-molecule acceptors for bulk heterojunctions as used in organic solar cells [18] the development of a universal strategy for ohmic hole injection into organic semiconductors with high ionization energies [19] and many others. [20][21][22][23][24][25] Another example is the development of strategies to harvest triplet excitons in organic light emitting diodes. For this purpose, novel classes of emitter molecules were developed, which include thermally activated delayed fluorescence (TADF)-based molecules, [26][27][28][29][30][31][32] rotationally accessed spin-state inversion, [33] and radical-based emitters. [34] Materials for organic electronics are presently used in prominent applications, such as displays in mobile devices, while being intensely researched for other purposes, such as organic photovoltaics, large-area devices, and thin-film transistors. Many of the challenges to improve and optimize these applications are material related and there is a nearly inf...

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Section: Mesoscalementioning

confidence: 99%

Toward Design of Novel Materials for Organic Electronics

et al. 2019

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“…It is common within the organic semiconductor community to model the total density of states (DOS) using a Gaussian distribution (alternative approaches using master equations have also been used [15,16]). Hopping charge transport in such a Gaussian DOS leads to a dependence of the (effective) mobility on the temperature, electric field, and charge-carrier density that has been parametrized by Pasveer et al and subsequently used in a series of papers describing unipolar transport in organic semiconductors [17,18].…”

Section: Introductionmentioning

confidence: 99%

Charge Transport in Spiro-OMeTAD Investigated through Space-Charge-Limited Current Measurements

et al. 2018

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Extracting charge-carrier mobilities for organic semiconductors from space-charge-limited conduction measurements is complicated in practice by nonideal factors such as trapping in defects and injection barriers. Here, we show that by allowing the bandlike charge-carrier mobility, trap characteristics, injection barrier heights, and the shunt resistance to vary in a multiple-trapping drift-diffusion model, a numerical fit can be obtained to the entire current density-voltage curve from experimental space-charge-limited current measurements on both symmetric and asymmetric 2; 2 0 ; 7; 7 0 -tetrakis(N; N-di-4-methoxyphenylamine)-9; 9 0 -spirobifluorene (spiro-OMeTAD) single-carrier devices. This approach yields a bandlike mobility that is more than an order of magnitude higher than the effective mobility obtained using analytical approximations, such as the Mott-Gurney law and the moving-electrode equation. It is also shown that where these analytical approximations require a temperature-dependent effective mobility to achieve fits, the numerical model can yield a temperature-, electric-field-, and charge-carrier-density-independent mobility. Finally, we present an analytical model describing trap-limited current flow through a semiconductor in a symmetric single-carrier device. We compare the obtained charge-carrier mobility and trap characteristics from this analytical model to the results from the numerical model, showing excellent agreement. This work shows the importance of accounting for traps and injection barriers explicitly when analyzing current density-voltage curves from space-charge-limited current measurements.

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“…It should be noted that for smaller thicknesses also the numerical model might no longer be applicable due to other effects becoming relevant, such as Coulomb correlations. 17 The major difference between the analytical and the numerical model is that in the numerical model the charge-carrier density and the electric field -and therefore the mobility -are dependent on the position across the semiconductor layer, whereas in the analytical description position-independent effective values are used. As demonstrated by the closely matched currentvoltage characteristics for both models, the use of these position-independent simplifications have negligible effects on the calculated current density.…”

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confidence: 99%

Analytical description of the current-voltage relationship in organic-semiconductor diodes

Wetzelaer

2018

AIP Advances

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The description of the current-voltage relationship in disordered organic-semiconductor diodes is complicated by the effects of diffusion and a charge-carrier mobility that depends on charge concentration, electric field and temperature. Here, an analytical model is presented that accurately describes the drift-diffusion current through disordered organic semiconductors over the full voltage range. The model applies to single-carrier devices in which the organic-semiconductor layer is situated between an Ohmic injecting contact and an extracting contact of which the barrier can be varied. The analytical description can be used to extract charge-transport parameters, such as mobility and energetic disorder, from experimental current-voltage characteristics of devices of virtually any layer thickness.

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Effect of Coulomb correlation on charge transport in disordered organic semiconductors

Cited by 33 publications

References 44 publications

Toward Design of Novel Materials for Organic Electronics

Toward Design of Novel Materials for Organic Electronics

Charge Transport in Spiro-OMeTAD Investigated through Space-Charge-Limited Current Measurements

Analytical description of the current-voltage relationship in organic-semiconductor diodes

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