Electrodeless measurement of charge carrier mobility in pentacene by microwave and optical spectroscopy techniques

Saeki, Akinori; Seki, Shu; Tagawa, Seiichi

doi:10.1063/1.2214638

Cited by 42 publications

(24 citation statements)

References 33 publications

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“…Therefore, we have only reported an FP-TRMC charge carrier mobility of 0.7 cm 2 V -1 s -1 as the minimum intragrain value, using a high-energy photon source capable of direct ionization. 49 Recently, our novel FI-TRMC technique revealed a hole mobility of 6.3 cm 2 V -1 s -1 , 32 matching the highest FET value and corroborating that TRMC mobility is relevant to charge transfer among adjacent molecules in crystalline molecular semiconductors.…”

Section: ⎟ ⎟ ⎠supporting

confidence: 65%

Charge carrier mobility in organic molecular materials probed by electromagnetic waves

Seki

Saeki

Sakurai

et al. 2014

Phys. Chem. Chem. Phys.

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137

129

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Charge carrier mobility is an essential parameter providing control over the performance of semiconductor devices fabricated using a variety of organic molecular materials. Recent design strategies toward molecular materials have been directed at the substitution of amorphous silicon-based semiconductors; accordingly, numerous measurement techniques have been designed and developed to probe the electronic conducting nature of organic materials bearing extremely wide structural variations in comparison with inorganic and/or metal-oxide semiconductor materials. The present perspective highlights the evaluation methodologies of charge carrier mobility in organic materials, as well as the merits and demerits of techniques examining the feasibility of organic molecules, crystals, and supramolecular assemblies in semiconductor applications. Beyond the simple substitution of amorphous silicon, we have attempted to address in this perspective the systematic use of measurement techniques for future development of organic molecular semiconductors.

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Section: ⎟ ⎟ ⎠supporting

confidence: 65%

Charge carrier mobility in organic molecular materials probed by electromagnetic waves

Seki

Saeki

Sakurai

et al. 2014

Phys. Chem. Chem. Phys.

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137

129

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“…2c and Figure S11). [14] It should be noted that such a clear acceleration of decay with a photon density was not always observed for other organic semiconductors, such as pentacene thin films deposited on a quartz substrate by thermal vapor deposition [20] and amorphous conjugated polymer films. [6,7,21] The single-crystal nature is anticipated to account for the clear dependence on photon density, while the many grain boundaries and chemical/physical defects in usual organic semiconductors would hide this dependence.…”

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confidence: 96%

Mobility and Dynamics of Charge Carriers in Rubrene Single Crystals Studied by Flash‐Photolysis Microwave Conductivity and Optical Spectroscopy

et al. 2008

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Organic semiconductors have evolved as a major class of plausible candidates for achieving low-cost, flexible, and highefficiency electric devices. In order to shed light on the intrinsic nature of charge-carrier transport in these materials, single-crystal rubrene, a tetraphenyl derivative of tetracene shown in Figure 1(a-b), is one of the most-appropriate benchmarks, due to the elimination of grain boundaries and minimization of charge-trapping sites. High hole mobility as high as 43 cm 2 V À1 s À1 measured by field-effect transistors (FET) has been reported. [1][2][3] By altering the metal work function of the electrodes, [4,5] Although numerous studies of rubrene single crystals using FET devices have been performed, a complete picture of the dynamics of the charge carriers has not been produced to date. To provide an insight into the optoelectronic properties of single-crystal rubrene, we investigated the charge-carrier dynamics and mobility by a combination of flash-photolysis time-resolved microwave conductivity (TRMC) and transient optical spectroscopy (TOS) techniques. [6,7] The former technique can predict the nanometer-scale mobility of charge carriers generated by a laser pulse under a low-power oscillating microwave electric field without an electrode attached, [8][9][10] so that it offers a measurement of the transient conductivity excluding metal-organic contact issues, reduction of charge-trapping effects, and anti-disturbance of the thermal motion of the charge carriers. The TOS experiment provides the transient photo-absorption (PA) spectrum/kinetics and the emission spectrum, of which the dependence of the incident photon density is compared with the TRMC results to discuss the intrinsic mobility of the charge carriers and the dynamics of the excitons and the charge carriers. We also demonstrate the anisotropic mobility in single-crystal rubrene by utilizing the fixed direction of the microwave electric field in a resonant cavity.[11-13] Figure 1c shows the transient PA spectrum together with the steady-state PA and emission spectra of single-crystal rubrene. The distinct peaks of the steady-state PA lie at 510, 480, and 450 nm, and are shifted towards shorter wavelength by about 15 nm with respect to those of isolated rubrene molecules in solution (Fig. S1). [14][15][16] The emission maximum is located at 630 nm which also shows a red-shift of about 60 nm relative to solution. This is suggestive of an excitonic state via the strong intermolecular interactions in crystalline rubrene as reported in the literature. [15] The transient PA spectrumshows a broad feature from the visible to the near-infrared region with two distinct peaks (835 and 895 nm). In order to assess the PA spectra of a radical cation (Ru · , hole) and a radical anion (Ru À , one excess electron) of rubrene molecules and their extinction coefficients (e), we performed a nanosecond electron-beam pulse radiolysis utilizing pyrene and biphenyl as mediators of electrons or holes, respectively ( Fig. S2-S6). [14] The results indic...

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“…Therefore, the high hole mobility of 6.3 cm 2 V −1 s −1 suggests that the transport mechanism for holes involves band conduction within a domain. It should also be noted that precise evaluation of hole mobility in pentacene by the FP-TRMC method has been limited so far, due to the lack of photo-induced charge carriers 37 . In that sense, the present work provides the first evaluation of intrinsic hole mobility in pentacene materials.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of Intrinsic Charge Carrier Transport at Insulator-Semiconductor Interfaces Probed by a Non-Contact Microwave-Based Technique

Honsho

Miyakai

Sakurai

et al. 2013

Sci Rep

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We have successfully designed the geometry of the microwave cavity and the thin metal electrode, achieving resonance of the microwave cavity with the metal-insulator-semiconductor (MIS) device structure. This very simple MIS device operates in the cavity, where charge carriers are injected quantitatively by an applied bias at the insulator-semiconductor interface. The local motion of the charge carriers was clearly probed through the applied external microwave field, also giving the quantitative responses to the injected charge carrier density and charge/discharge characteristics. By means of the present measurement system named field-induced time-resolved microwave conductivity (FI-TRMC), the pentacene thin film in the MIS device allowed the evaluation of the hole and electron mobility at the insulator-semiconductor interface of 6.3 and 0.34 cm2 V−1 s−1, respectively. This is the first report on the direct, intrinsic, non-contact measurement of charge carrier mobility at interfaces that has been fully experimentally verified.

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Electrodeless measurement of charge carrier mobility in pentacene by microwave and optical spectroscopy techniques

Cited by 42 publications

References 33 publications

Charge carrier mobility in organic molecular materials probed by electromagnetic waves

Charge carrier mobility in organic molecular materials probed by electromagnetic waves

Mobility and Dynamics of Charge Carriers in Rubrene Single Crystals Studied by Flash‐Photolysis Microwave Conductivity and Optical Spectroscopy

Evaluation of Intrinsic Charge Carrier Transport at Insulator-Semiconductor Interfaces Probed by a Non-Contact Microwave-Based Technique

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