Charge transport in doped organic semiconductors

Shen, Yulong; Diest, Kenneth; Wong, Man Hoi; Hsieh, B.J.; Dunlap, David; Malliaras, George G.

doi:10.1103/physrevb.68.081204

Cited by 74 publications

(62 citation statements)

References 26 publications

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“…Up to this high ratio of dopant, a TFT behavior could be observed and therefore meaningful values for the mobility could be obtained. The nonlinear behavior of the mobility of the oxidized pTPD as a function of the dopant ratio exactly follows the prediction made from the model put forward by Shen et al, 15 which is due to a combined effect of dipolar broadening of the DOS and manifold filling. The initial decrease in mobility can be explained by the increase in the broadening of the transport manifold due to the enhanced disorder coming from the dopant.…”

supporting

confidence: 52%

“…In fact, the partial oxidation of arylamines, although resulting in an increase in conductivity, is still not completely understood. In their paper, Shen et al 15 describe the competing influence of at least three processes on the increase in conductivity. These are the increase of the width of the distribution of the density of states ͑DOS͒ due to an increased polarity by the partial oxidation, the Coulombic interaction between the delocalized charge on the arylamine and its counterion and the partial filling of the transport manifold.…”

mentioning

confidence: 99%

“…[12][13][14] The possibility of improving the mobility of such materials has been demonstrated and reported using various approaches. 7,8,[12][13][14][15] For example, it is possible to modify the polymer chain by anchoring end-capping groups, 12 to use them as dopant for inert polymers such as polystyrene or polycarbonate, 7,13,14 or to oxidize the arylamines with strong oxidant molecules such as ClO 4 − and AgSbF 6 . 8, 15 Recently, Bolink et al 6,16 have shown that pTPD properties can be modified by oxidizing it with a molecular magnetic cluster ͓Mn 12 O 12 ͑H 2 O͒ 4 ͑C 6 F 5 COO͒ 16 ͔.…”

mentioning

confidence: 99%

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Increased conductivity of a hole transport layer due to oxidation by a molecular nanomagnet

Cheylan

Puigdollers

Bolink

et al. 2008

Journal of Applied Physics

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Thin film transistors based on polyarylamine poly͑N , NЈ-diphenyl-N , NЈbis͑4-hexylphenyl͒-͓1,1Јbiphenyl͔-4,4Ј-diamine ͑pTPD͒ were fabricated using spin coating in order to measure the mobility of pTPD upon oxidation. Partially oxidized pTPD with a molecular magnetic cluster showed an increase in mobility of over two orders of magnitude. A transition in the mobility of pTPD upon doping could also be observed by the presence of a maximum obtained for a given oxidant ratio and subsequent decrease for a higher ratio. Such result agrees well with a previously reported model based on the combined effect of dipolar broadening of the density of states and transport manifold filling. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2917304͔In recent years, there have been increasing interests and research activities in the field of organic light-emitting devices ͑OLEDs͒. The promise of the use of this technology in flat panel displays through the fabrication of low-cost and flexible electronic devices has been the main driving force. Although enormous progress has been achieved in improving the luminance efficiency, color fidelity, and device lifetime, there is a continuous effort for a better stability of the device toward commercialization. Interface engineering between the electrodes and the emitting layer is important for the improvement of the device lifetime as well as luminous efficiency in OLEDs and has lead to the fabrication of multilayer devices, with charge transport and charge injection layer ͑HIL͒ deposited by vacuum sublimation technique. 1,2 In terms of solution processable OLEDs, such as polymer based light emitting devices ͑PLEDs͒, the use of a PEDOT-PSS layer as the HIL is well known to improve the hole injection from the indium tin oxide ͑ITO͒ as well as planarizing the ITO surface and has been well studied. 3,4 Although it has shown improved device performance such as lower operational voltage and higher luminance efficiency, other problems render it not suitable for device stability. For example, it is found that the ITO/PEDOT-PSS interface is not stable due to the etching of ITO by the strong acidic nature of PSS. 5 Therefore, at this stage of PLED development, the search for other better solution processable HIL material is needed and it is much required to modify the HIL to further improve the device lifetime as well as its efficiency. Following such an approach, recent results by Bolink et al. 6 have shown that a solution processable HIL material can be used for PLEDs and showed improved performance as when using PEDOT-PSS. Such HIL material is based on a polyarylamine poly͑N , NЈ-diphenyl-N , NЈbis͑4-hexylphenyl͒-͓1,1Јbiphenyl͔-4,4Ј-diamine ͑pTPD͒ which was doped with a molecular magnet and showed tunable conductivity depending on the level of doping. The diamine derivative pTPD resembles very closely to the well known and intensively used organic molecule N , NЈ-diphenyl-N , NЈbis͑3-methylphenyl͒-͓1,1Јbiphenyl͔-4,4Ј-diamine ͑TPD͒, while being processable by the spin coating technique and...

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supporting

confidence: 52%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Increased conductivity of a hole transport layer due to oxidation by a molecular nanomagnet

Cheylan

Puigdollers

Bolink

et al. 2008

Journal of Applied Physics

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“…This Gaussian density of states reflects the energetic spread in the transport sites due to disorder. For organic materials is typically around 0.1 eV; [30][31][32][33][34] this value is used throughout this paper unless stated otherwise. To sample the average behaviors of carriers, multiple morphologies with the same characteristics ͑b, ␣, and ͒ are generated.…”

Section: Modelmentioning

confidence: 99%

Charge carrier mobility in disordered organic blends for photovoltaics

Koster

2010

Phys. Rev. B

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Please check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement: www.tue.nl/taverne Take down policyIf you believe that this document breaches copyright please contact us at: openaccess@tue.nl providing details and we will investigate your claim. Charge transport in disordered organic blends is studied theoretically by numerically solving the Pauli master equation. The influence of morphology, disorder, electric field, and charge carrier concentration on blend mobility is assessed. Important differences between neat materials and blends are found. The dependence of mobility on charge carrier concentration is more pronounced in blends and it is influenced by the electric field strength. At low charge carrier densities, blend mobility is found to decrease with increasing field. Additionally, the impact of the volume ratio of the constituent materials and their domain size on the mobility is presented. Especially for strongly disordered materials charge transport is favored by relatively large domains. To compare these theoretical findings with existing experimental mobility data, the current density in a space-charge-limited device is computed. The author finds that, for the parameters and morphologies studied, the apparent mobility in such a device decreases with increasing bias voltage.

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“…Oxygen has been observed to increase the carrier concentration of CuPc by many orders [14]. Inside the CuPc, oxygen acts as a dopant, which also causes broadening of DOS due to columbic trapping [15] and dipole effect [16,17]. The width of DOS is related to the ARTICLE IN PRESS Fig.…”

Section: Resultsmentioning

confidence: 97%