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. 2017 Jan 20;2(1):164–170. doi: 10.1021/acsomega.6b00428

Rapid Evaluation of Electron Mobilities at Semiconductor–Insulator Interfaces in an Ambient Atmosphere by a Contactless Microwave-Based Technique

Junichi Inoue †, Yusuke Tsutsui †, Wookjin Choi †, Kai Kubota †,‡, Tsuneaki Sakurai †,*, Shu Seki †,*
PMCID: PMC6640973  PMID: 31457218

Abstract

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Intrinsic mobility of electrons at the interfaces between crystalline organic semiconductors and insulating dielectric polymer films was rapidly evaluated in an ambient atmosphere by TRMC@Interfaces, a noncontact and nondestructive method based on dielectric loss spectroscopy of microwaves. By just preparing simple metal–insulator–semiconductor devices, local-scale motions of charge carriers injected into the interface by pulses of gate bias voltage were monitored through reflected microwave changes, resulting in the evaluation of local-scale charge carrier mobilities together with the value of trap density at the interface. The evaluated high electron mobilities of 12 cm2 V–1 s–1 for N,N′-bis(cyclohexyl)naphthalene-1,4,5,8-bis(dicarboximide) (DCy-NDI) and 15 cm2 V–1 s–1 for N,N′-dioctylperylene-1,4,5,8-bis(dicarboximide) (DC8-PDI) are the benchmarks for organic semiconducting materials that are comparable with the highest ones reported from the field-effect transistor devices. The present TRMC@Interfaces was found to serve as a rapid screening technique to examine the intrinsic performance of organic semiconducting materials as well as a useful tool enabling the precise discussion on the relationship among their local-scale charge carrier mobility, thin-film morphology, and packing structure.

Introduction

Versatile and convenient methods to access the charge carrier transport property of organic semiconductors are highly in demand along with the recent progress of organic electronics. Representative techniques commonly used so far include the Hall effect, field-effect transistors (FETs), time-of-flight, and space charge limited current, where the long-range translational motion of the generated/injected charge carriers (hole or electron) contributes to the analytical theories used in their evaluation processes. The FET method has attracted particular attention because FETs work as switching devices important for integrated circuits.1−4 However, FET has several requisites to operate, such as proper injection of electrons from a source to the semiconductor layer, and then to drain. Thus, a tedious device optimization process is required before FET operation, resulting in the time-consuming issue to judge the potential of the target semiconducting materials. Microwave dielectric loss spectroscopy has provided an electrodeless platform for the measurement of local-scale motion of charge carriers injected by ionizing radiations,5,6 photocarrier injection into organic heterojunctions,7−9 and/or inorganic semiconductors,10,11 demonstrating the versatile and prompt diagnosis of mobility free from the device optimization processes. A planar microstrip microwave resonator was also designed, offering a wide flexibility of the measurement system for electron/hole-transporting semiconductor films.12 We have recently developed a microwave-based evaluation technique (time-resolved microwave conductivity: TRMC@Interfaces)13−17 that uses dielectric loss spectroscopy of field-induced charge carriers in simple metal–insulator–semiconductor (MIS) devices. In this method, hole or electron carriers are injected at the insulator–semiconductor interfaces of the MIS device by applying pulse gate bias (Vg) (Figure 1b). Simultaneously, the local-scale motions of the charge carriers are independently monitored by microwave-based dielectric loss spectroscopy toward the MIS device set in a resonant cavity. This fully experimental technique eventually provides local-scale, intrinsic hole/electron mobility as well as trap density particularly at the insulator–semiconductor interfaces. Using this technique, we have reported the mobility of pentacene and heteroacene derivatives, revealing high intrinsic hole mobilities (e.g., ∼6 cm2 V–1 s–1 for pentacene).13,14 In the present study, we focused on the rapid evaluation of the electron transport property even in an ambient atmosphere with the TRMC@Interfaces technique. Investigating n-type semiconducting character is a more challenging issue than that of holes due to the effect of impurities containing water and oxygen that severely inhibit the long-range translational motion of electrons in the device.23 Thus, evaluation of electron transport property has mostly been addressed under high-vacuum conditions. Here, we tried to determine electron mobilities of relatively air-stable arylenediimides in an ambient atmosphere with a simple device structure. Because the characterized mobilities are dominantly based on the intragrain motion, the observed high-mobility values were discussed correlating with the crystalline order of semiconducting molecules.

Figure 1.

Figure 1

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(a) Molecular structures of organic semiconductors used in this study. (b) Schematic diagram of the microwave circuit of TRMC@Interfaces measurements, direction of electric field by microwave, and configuration of the MIS device.

Results and Discussion

N,N-bis(cyclohexyl)naphthalene-1,4,5,8-bis(dicarboximide) (DCy-NDI),18N,N′-dioctylperylene-1,4,5,8-bis(dicarboximide) (DC8-PDI),19 and N,N′-bis(cyclohexyl)perylene-1,4,5,8-bis(dicarboximide) (DCy-PDI)20 are chosen as semiconducting layer materials (Figure 1a) because these are well-known n-type materials applied in FETs and organic photovoltaic devices.21,22 MIS devices were fabricated according to the previous reports13,14 (see the Experimental Section). The microwave circuit was constructed using a waveguide system with a homodyne setup (Figure 1b) and our previous report.13 Other detailed experimental methods are described in the Experimental Section. As shown in Figure S1 (Supporting Information), the resonance of microwave was successfully obtained when a MIS device was loaded in the cavity. It should be noted that the change in the capacitance value upon applied gate bias was monitored by means of the displacement current measurement (DCM) of the MIS device, suggesting that charge carriers were certainly injected into the insulator–semiconductor interface (Figure S2).

Evaluation of Electron Mobility for DCy-NDI in an Ambient Atmosphere and at Controlled Temperature

Figure 2 shows typical microwave and current transients for a DCy-NDI-based MIS device. After the MIS device was set in the cavity, a 50 ms pulse gate bias (Vg(t)) was applied to inject electrons at the DCy-NDI–poly(methyl methacrylate) (PMMA) interface. Accordingly, electric current (I(t)) was monitored, which can be converted to the charge amount (q(t)) profile by integrating I(t) with time (Figure 2a). In parallel with the current-flow monitoring, the changes in reflected microwave power (ΔPr(t)) were confirmed to respond to the gate bias voltages (Figure 2b). Although the relatively slow decay of ΔPr at 50–80 ms in Figure 2b suggested the presence of some barrier for the discharging process of electrons, the shape of the ΔPr(t) curves was basically similar to that of the q(t) traces, proving that the resulted dielectric loss phenomenon was contributed by the injected electrons. In the TRMC@Interfaces measurement, the transient dielectric loss (Δ(1/Q)) in the cavity is proportional to the conductivity changes (Δσ)

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where e, ε, ω, and Δn are the elementary charge, dielectric constant, angular frequency of microwave, and change in the charge carrier density, respectively. The linearity between ΔPr and Δ(1/Q) was preserved in the present range of ΔPr,13 and hence, the pseudoconductivity (ΔNμ) was calculated from the saturated value of ΔPr for each Vg using the reported calibration equation below.13

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On the other hand, the numbers of injected charge carriers (Ninj) were easily calculated from the saturated value of q(t) (at 50 ms). From the sets of pseudoconductivity ΔNμ and injected carriers Ninj, the Ninj–ΔNμ plot was obtained (Figure 2c), where the first derivative represents electron mobility. It comprises four regions: (i) the silent region of Ninj < 0.5 × 1011, (ii) high-mobility region, (iii) slightly lower mobility region, and (iv) saturation region. The first silent region corresponds to carrier trapping at the interface (ntrap ∼ 5 × 1011 cm–2).14 After filling up the traps, the second region appears where a higher mobility is estimated than that of region (iii). We consider that this second region reflects intrabulk mobility. With a weak gate bias, charge carriers are injected not only at the interface but also into the bulk region because of thermal diffusion.24 As the interface is affected by the random potential of insulators, it can be expected that the bulk mobility is higher than that near the interface. For this reason, we ascribed the mobility estimated from region (iii) to the interfacial mobility. Application of further higher gate voltages results in the saturation of the mobility (iv). The explanation of high-injection region is debatable, but there is a clue to elucidate this phenomenon: the saturation of microwave signal in the high-injection regime completely disappears under vacuum conditions (Figure S3). This contrast was observed in different devices with reproducibility. We, at present, have no absolute evidence but suppose that oxygen or water molecules could deteriorate the conduction of electron in the high concentration of anionic species. It should be noted that the estimated mobility (slope) was comparable between ambient atmosphere and vacuum conditions for each DCy-NDI device.

Figure 2.

Figure 2

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(a) Typical time profiles of the amount of accumulated charge carriers in the DCy-NDI MIS device. (b) Typical time profiles of change in reflected microwave power in the DCy-NDI MIS device. (c) Correlation between the pseudo-electrical conductivity, ΔNμ, and the number of injected charge carriers, Nin, in the DCy-NDI MIS device. (d) X-ray diffraction (XRD) patterns of DCy-NDI MIS devices used in TRMC@Interfaces measurements. (e) AFM image together with the height profile (along the line in the image) of semiconductor layer surfaces of the DCy-NDI MIS device.

The XRD analysis of the DCy-NDI MIS device revealed an ordered layer structure (d100 = 18.1 Å) of NDI cores (Figure 2d), where the layer distance agrees with the reported single crystal structure.20,25 A smooth surface of polycrystalline semiconducting layer with a small root-mean-square roughness of 4.0 nm was visualized by atomic force microscopy (AFM) (Figure 2e and Table S1). The transport mechanism of the local-scale motions of these highly mobile charge carriers is another important subject. The prototype of low-temperature TRMC@Interfaces systems has been developed to approach the temperature dependence of carrier mobility. As a trial using the DCy-NDI-based MIS device, the obtained Ninj–ΔNμ plot from 210 to 300 K indicated a slightly positive correlation between temperature and electron mobility with a small activation energy of ∼60 meV (Figure S4). This observation implies that the local-scale electron conduction at the DCy-NDI/PMMA interface relies principally on a hopping-like mechanism, though there is a large electron mobility of ∼10 cm2 V–1 s–1.26

Evaluation of Electron Mobility for DCy-PDI and DC8-PDI in an Ambient Atmosphere

To screen a series of n-type materials for TRMC@interfaces, DCy-PDI MIS devices were investigated under an identical vapor-deposition condition to that of DCy-NDI. The proposed core-size effect,27 where a larger π-system is favorable for intermolecular charge transport in view of Marcus theory, was another important interesting subject by studying extended π-conjugated materials with the present TRMC technique probing local-scale charge carrier motions. However, the microwave response was very small for the DCy-PDI MIS device (Figure 3a), and it is difficult to distinguish with noise signals. In fact, mobility evaluation is not possible from the Ninj–ΔNμ plot (Figure 3c). The observation of film morphology and measurement of packing structure indicated that the DCy-PDI film formed a different packing structure from the reported crystalline phase.28 One of the striking features in the observed XRD pattern was the lamellar periodicity of d′001 = 28.9 Å that was far larger than the reported axes (Figure 3e).27 It is probably because PDI cores have a strong intermolecular π–π interaction and thus are trapped to form a kinetically stabilized structure at the PMMA surface at room temperature (r.t.). With this hypothesis, a new MIS device was fabricated by controlling the substrate temperature (Tsub) at 80 °C during the vapor deposition. Then, a set of sharp diffraction peaks was observed (Figure 3f), where the spacing of d001 = 18.4 Å corresponds to one of the reported lattices.28 Moreover, AFM images disclosed that the crystalline grains of the DCy-PDI surface (Figure 3h) were highly developed with Tsub = 80 °C rather than the case with Tsub = r.t. As a consequence, a small but significant increase in the microwave response was observed (Figure 3b). The estimated electron mobility by TRMC@interfaces is μe = 0.2 cm2 V–1 s–1 (Figure 3d).

Figure 3.

Figure 3

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Typical time profiles of the change in the reflected microwave power in the DCy-PDI MIS device at substrate temperatures of (a) r.t. and (b) 80 °C during vapor deposition. Correlation between the pseudo-electrical conductivity, ΔNμ, and the number of injected charge carriers, Nin, in DCy-PDI devices at substrate temperatures of (c) r.t. and (d) 80 °C during vapor deposition. XRD patterns of DCy-PDI MIS devices, used in TRMC@Interfaces measurements, at substrate temperatures of (e) r.t. and (f) 80 °C during vapor deposition. AFM image together with the height profile (along the line in the image) of semiconductor layer surfaces of DCy-PDI MIS devices at substrate temperatures of (g) r.t. and (h) 80 °C during vapor deposition.

Another PDI derivative, DC8-PDI, was examined in a similar way by preparing two types of MIS devices with Tsub = r.t. and 80 °C. As the π–π stacking tendency was more obvious for this system, drastic difference in TRMC@interfaces measurements was confirmed. However, in this case, we concluded that the difference originated from the uniformity of the films that determine the sufficient/insufficient injection of electrons at the PMMA–DC8-PDI interface. In the case of Tsub = r.t., an estimated electron mobility of μe = 0.9 cm2 V–1 s–1 was recorded (Figure 4a). Although the obtained weak diffraction peaks in XRD were likely assigned to a reported crystalline packing (Figure 4c),29,30 AFM observation revealed that the semiconductor layer was composed of nonuniform aggregates (Figure 4e) probably due to the very strong π–π interactions. On the assumption of the homogeneous distribution of charges accumulated at the PMMA–DC8-PDI and Au–PMMA interfaces, the calculated mobility is presumed to be underestimated. In contrast, for the MIS device with Tsub = 80 °C, a uniform polycrystalline film was given (Figure 4d,f), leading to the local-scale electron mobility of μe = 15 cm2 V–1 s–1 (Figure 4b).

Figure 4.

Figure 4

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Correlation between the pseudo-electrical conductivity, ΔNμ, and the number of injected charge carriers, Nin, in DC8-PDI devices at substrate temperatures of (a) r.t. and (b) 80 °C during vapor deposition. XRD patterns of DC8-PDI MIS devices, used in TRMC@Interfaces measurements, at substrate temperatures of (c) r.t. and (d) 80 °C during vapor deposition. AFM image together with the height profile (along the line in the image) of semiconductor layer surfaces of DC8-PDI MIS devices at substrate temperatures of (e) r.t. and (f) 80 °C during vapor deposition.

Spatial Size of Mobile Charge Carriers and Structure–Mobility Correlations

On the basis of Kubo’s equation derived from the Einstein–Smoluchowski relation31

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the spatial size (Δx) of statistical local motion of charge carriers was estimated during the turn-over period of the electric field of the 9 GHz microwave (see the Supporting Information in detail). As summarized in Table 1, the Δx values range from 5 to 66 nm, all of which appear much smaller than the crystalline grain size, judging from the corresponding AFM images (Table S1). Therefore, the evaluated mobility dominantly reflects the intragrain charge carrier motions at semiconductor–insulator interfaces.

Table 1. Summary of the Parameters Studied by TRMC@Interfacesa.

  Tsub μe (cm2 V–1 s–1) ntrap (cm–2) Δx (nm)
DCy-NDI r.t. 12 5 × 1011 59
DCy-PDI r.t. b c 5
80 °C 0.2 c 8
DC8-PDI r.t. b c  
80 °C 15 2 × 1011 66
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a

Substrate temperature during vacuum deposition of semiconductors (Tsub), evaluated electron mobilities (μe), trap density at the interface, and diffusion length of the charge carriers using the 9 GHz microwave.

b

Not applicable for estimation of mobilities.

c

Not applicable for estimation of trap density.

The relationship between local-scale structure and property can be discussed on the basis of the XRD patterns and charge carrier mobility evaluated by TRMC@interfaces. It is considered that the observed difference between the local-scale electron mobilities of DCy-PDI and DC8-PDI is dominantly due to the dimensionality of the electron transport pathways. DC8-PDIs adopt a herringbone structure29,30 that enables two-dimensional conductive routes parallel to the direction of the electric field of the microwave, whereas electron transport pathways of DCy-PDIs align linearly28 parallel to the electric field. Even in the local area probed by the present TRMC@interfaces method, thermal fluctuations at r.t. may disturb the one-dimensional conductive pathways of charge carriers, whereas the two-dimensional conductive network is less affected.

Conclusions

As exemplified by the simple MIS devices containing a series of arylenediimide derivatives, we demonstrated the evaluation of local-scale, intrinsic electron mobility at insulator–semiconductor interfaces even in an ambient atmosphere. The estimated mobility values reflect nanometer-scale motion of the injected charge carriers at the interface. In fact, the mobility values are mostly larger than those reported for FET devices and comparable with the highest ones reported so far, suggesting the benchmark charge carrier mobilities of target semiconducting materials. We believed that the present TRMC@Interfaces method serves as a rapid screening technique as well as a useful tool to discuss the relationship among the local-scale charge carrier mobility, thin-film morphology, and packing structure of organic semiconductors.

Experimental Section

Fabrication of MIS Devices

The MIS devices used in this study were fabricated as follows: (1) A quartz substrate (4.9 × 50 mm2, 1 mm thick) was treated with UV–O3 before use; (2) Ti (adhesion layer, 5 nm) and Au (gate electrode, 30 nm) layers were successively deposited on the quartz substrate by direct-current sputtering and thermal vacuum deposition, respectively; (3) As insulating layers, a 300 nm-thick SiO2 layer was deposited by radio-frequency sputtering, and a 250 nm-thick PMMA (Aldrich) layer was deposited by spin-coating from a 3 wt % PMMA solution in toluene; (4) Thermal annealing was carried out at 100 °C for 1 h to remove residual solvent; (5) DCy-NDI, DC8-PDI, or DCy-PDI (Figure 1a), of 30–50 nm thickness, was thermally evaporated at a rate of 0.03 nm s–1 under 2 × 10–4 Pa; (6) A 30 nm-thick top Au electrode was deposited by vacuum deposition.

TRMC@Interfaces Measurements

The microwave circuit was constructed using a waveguide system with a homodyne setup, as described in Figure 1b and our previous report.13 The TRMC@Interfaces measurements were carried out using a microwave at 9 GHz from a signal generator (SMF 100A; Rohde & Schwarz). After the MIS device was loaded in the microwave cavity, a pulse gate bias voltage Vg(t) at an interval of 50 ms was applied based on a multifunction generator (WF 1973; NF Corporation). The current injected into the semiconductor–insulator interface I(t) was monitored using a digital phosphor oscilloscope (MDO 3022; Tektronix). Simultaneously, the reflected microwave Pr(t) is first amplified with a high gain FET amplifier (Gain 30 dB, 8–12 GHz; Ciao CA812-304), then picked up by a Schottky diode, and monitored by the oscilloscope. All experiments were conducted under ambient atmosphere at r.t.

Characterization of Semiconducting Layers

The morphology of semiconducting layers was characterized by a tapping-mode atomic force microscope (SPI-4000, Nanonavi II; SII NanoTechnology) using silicon cantilevers with a frequency of 150 kHz and spring constant of 9 N/m (OMCL-AC200TS-R3; OLYMPUS). The molecular packing of semiconducting layers was analyzed by XRD measurements using an X-ray diffractometer (λ = 1.54 Å, MiniFlex600; Rigaku) with a semiconductor detector (D/teX Ultra; Rigaku).

DCMs

Triangle voltage was applied to the MIS devices by a function generator (WF 1973; NF Corporation) equipped with a voltage amplifier. Transient current Idis(t) was picked up by a 30 kΩ terminal resistor serially connected to the MIS device and monitored by a digital oscilloscope (MDO 3022; Tektronix). On the basis of the following equation, the capacitance values were calculated.

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Acknowledgments

This work was partially supported by a Grant-in-Aid for Scientific Research (Nos. 26620104 and 26102011) from the Japan Society for the Promotion of Science (JSPS), ELCAS program at Kyoto University from the Japan Science and Technology Agency (JST), Casio Science Promotion Foundation, Shorai Foundation for Science and Technology, The Murata Science Foundation, The Scholar Program of Toyota Physical & Chemical Research Institute, Sumitomo Electric Group Corporate Social Responsibility Foundation, Asahi Glass Foundation, and Kato Foundation for Promotion of Science. Y.T. and W.C. thank the JSPS for a Young Scientist Fellowship. K.K. thanks ELCAS program at Kyoto University from JST.

Supporting Information Available

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.6b00428.

  • Reflected microwave power spectrum, DCM results, Ninj–ΔNμ plot under vacuum, temperature dependence of electron mobility, summary of averaged grain size and root-mean-square roughness, discussion on the charge carrier injection in MIS devices, discussion on the relationship between crystalline sizes and diffusion length of carriers (PDF)

The authors declare no competing financial interest.

Supplementary Material

ao6b00428_si_001.pdf (281.2KB, pdf)

References

  1. Farchioni R.; Grosso G.. Organic Electronic Materials; Springer-Verlag: Berlin, 2001. [Google Scholar]
  2. Bao Z.; Locklin J.. Organic Field-Effect Transistors; CRC Press: Boca Raton, 2007. [Google Scholar]
  3. Sirringhaus H. Device Physics of Solution-Processed Organic Field-Effect Transistors. Adv. Mater. 2005, 17, 2411–2425. 10.1002/adma.200501152. [DOI] [Google Scholar]
  4. Klauk H. Organic thin-film transistors. Chem. Soc. Rev. 2010, 39, 2643–2666. 10.1039/b909902f. [DOI] [PubMed] [Google Scholar]
  5. Grozema F. C.; Siebbeles L. D. A. Charge Mobilities in Conjugated Polymers Measured by Pulse Radiolysis Time-Resolved Microwave Conductivity: From Single Chains to Solids. J. Phys. Chem. Lett. 2011, 2, 2951–2958. 10.1021/jz201229a. [DOI] [Google Scholar]
  6. Charge and Exciton Transport through Molecular Wires; Grozema F. C., Siebbeles L. D. A., Eds.; Wiley-VCH Verlag & Co. KGaA: Weinheim, 2001; pp. 239–270. [Google Scholar]
  7. Saeki A.; Yoshikawa S.; Tsuji M.; Koizumi Y.; Ide M.; Vijayakumar C.; Seki S. A Versatile Approach to Organic Photovoltaics Evaluation Using White Light Pulse and Microwave Conductivity. J. Am. Chem. Soc. 2012, 134, 19035–19042. 10.1021/ja309524f. [DOI] [PubMed] [Google Scholar]
  8. Park J.; Reid O. G.; Rumbles G. Photoinduced Carrier Generation and Recombination Dynamics of a Trilayer Cascade Heterojunction Composed of Poly(3-hexylthiophene), Titanyl Phthalocyanine, and C60. J. Phys. Chem. B 2015, 119, 7729–7739. 10.1021/acs.jpcb.5b00110. [DOI] [PubMed] [Google Scholar]
  9. Ihly R.; Mistry K. S.; Ferguson A. J.; Clikeman T. T.; Larson B. W.; Reid O.; Boltalina O. V.; Strauss S. H.; Rumbles G.; Blackburn J. L. Tuning the driving force for exciton dissociation in single-walled carbon nanotube heterojunctions. Nat. Chem. 2016, 8, 603–609. 10.1038/nchem.2496. [DOI] [PubMed] [Google Scholar]
  10. Fravventura M. C.; Siebbeles L. D. A.; Savenije T. J. Mechanisms of Photogeneration and Relaxation of Excitons and Mobile Carriers in Anatase TiO2. J. Phys. Chem. C 2014, 118, 7337–7343. 10.1021/jp500132w. [DOI] [Google Scholar]
  11. Saeki A.; Yasutani Y.; Oga H.; Seki S. Frequency-Modulated Gigahertz Complex Conductivity of TiO2 Nanoparticles: Interplay of Free and Shallowly Trapped Electrons. J. Phys. Chem. C 2014, 118, 22561–22572. 10.1021/jp505214d. [DOI] [Google Scholar]
  12. Zarifi M. H.; Mohammadpour A.; Farsinezhad S.; Wiltshire B. D.; Nosrati M.; Askar A. M.; Daneshmand M.; Shankar K. Time-Resolved Microwave Photoconductivity (TRMC) Using Planar Microwave Resonators: Application to the Study of Long-Lived Charge Pairs in Photoexcited Titania Nanotube Arrays. J. Phys. Chem. C 2015, 119, 14358–14365. 10.1021/acs.jpcc.5b01066. [DOI] [Google Scholar]
  13. Honsho Y.; Miyakai T.; Sakurai T.; Saeki A.; Seki S. Evaluation of Intrinsic Charge Carrier Transport at Insulator-Semiconductor Interfaces Probed by a Non-Contact Microwave-Based Technique. Sci. Rep. 2013, 3, 3182 10.1038/srep03182. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Choi W.; Miyakai T.; Sakurai T.; Saeki A.; Yokoyama M.; Seki S. Non-contact, non-destructive, quantitative probing of interfacial trap sites for charge carrier transport at semiconductor-insulator boundary. Appl. Phys. Lett. 2014, 105, 033302 10.1063/1.4891052. [DOI] [Google Scholar]
  15. Tsutsui Y.; Sakurai T.; Minami S.; Hirano K.; Satoh T.; Matsuda W.; Kato K.; Takata M.; Miura M.; Seki S. Evaluation of Intrinsic Charge Carrier Transporting Properties of Linear- and Bent-Shaped π-Extended Benzo-Fused Thieno[3,2-b]thiophenes. Phys. Chem. Chem. Phys. 2015, 17, 9624–9628. 10.1039/C5CP00785B. [DOI] [PubMed] [Google Scholar]
  16. Tsutsui Y.; Schweicher G.; Chattopadhyay B.; Sakurai T.; Arlin J.-B.; Ruzié C.; Aliev A.; Ciesielski A.; Colella S.; Kennedy A. R.; Lemaur V.; Olivier Y.; Hadji R.; Sanguinet L.; Castet F.; Osella S.; Dudenko D.; Beljonne D.; Cornil J.; Samorì P.; Seki S.; Geerts Y. H. Unraveling Unprecedented Charge Carrier Mobility through Structure Property Relationship of Four Isomers of Didodecyl[1]benzothieno[3,2-b][1]benzothiophene. Adv. Mater. 2016, 28, 7106–7114. 10.1002/adma.201601285. [DOI] [PubMed] [Google Scholar]
  17. Seki S.; Saeki A.; Sakurai T.; Sakamaki D. Charge carrier mobility in organic molecular materials probed by electromagnetic waves. Phys. Chem. Chem. Phys. 2014, 16, 11093–11113. 10.1039/c4cp00473f. [DOI] [PubMed] [Google Scholar]
  18. Shukla D.; Nelson S. F.; Freeman D. C.; Rajeswaran M.; Ahearn W. G.; Meyer D. M.; Carey J. T. Thin-Film Morphology Control in Naphthalene-Diimide-Based Semiconductors: High Mobility n-Type Semiconductor for Organic Thin-Film Transistors. Chem. Mater. 2008, 20, 7486–7491. 10.1021/cm802071w. [DOI] [Google Scholar]
  19. Chesterfield R. J.; McKeen J. C.; Newman C. R.; Ewbank P. C.; Filho D. A. D. S.; Bredas J.-L.; Miller L. L.; Mann K. R.; Frisbie C. D. Organic Thin Film Transistors Based on N-Alkyl Perylene Diimides: Charge Transport Kinetics as a Function of Gate Voltage and Temperature. J. Phys. Chem. B 2004, 108, 19281–19292. 10.1021/jp046246y. [DOI] [Google Scholar]
  20. Locklin J.; Li D.; Mannsfeld S. C. B.; Borkent E.-J.; Meng H.; Advincula R.; Bao Z. Organic Thin Film Transistors Based on Cyclohexyl-Substituted Organic Semiconductors. Chem. Mater. 2005, 17, 3366–3374. 10.1021/cm047851g. [DOI] [Google Scholar]
  21. Anthony J. E.; Facchetti A.; Heeney M.; Marder S. R.; Zhan X. n-Type organic semiconductors in organic electronics. Adv. Mater. 2010, 22, 3876–3892. 10.1002/adma.200903628. [DOI] [PubMed] [Google Scholar]
  22. Gsänger M.; Bialas D.; Huang L.; Stolte M.; Würthner F. Organic Semiconductors based on Dyes and Color Pigments. Adv. Mater. 2016, 28, 3615–3645. 10.1002/adma.201505440. [DOI] [PubMed] [Google Scholar]
  23. Zhou K.; Dong H.; Zhang H.-l.; Hu W. High performance n-type and ambipolar small organic semiconductors for organic thin film transistors. Phys. Chem. Chem. Phys. 2014, 16, 22448–22457. 10.1039/C4CP01700E. [DOI] [PubMed] [Google Scholar]
  24. Takeya J.; Yamagishi M.; Tominari Y.; Hirahara R.; Nakazawa Y.; Nishikawa T.; Kawase T.; Shimoda T.; Ogawa S. Very high-mobility organic single-crystal transistors with in-crystal conduction channels. Appl. Phys. Lett. 2007, 90, 102120 10.1063/1.2711393. [DOI] [Google Scholar]
  25. Adiga S. P.; Shukla D. Electronic Structure and Charge-Transport Properties of N,N′-Bis(cyclohexyl)naphthalene Diimide. J. Phys. Chem. C 2010, 114, 2751–2755. 10.1021/jp9096937. [DOI] [Google Scholar]
  26. Warta W.; Stehle R.; Karl N. Ultrapure, high mobility organic photoconductors. Appl. Phys. A. 1985, 36, 163–170. 10.1007/BF00624938. [DOI] [Google Scholar]
  27. van de Craats A. M.; Warman J. M. The Core-Size Effect on the Mobility of Charge in Discotic Liquid Crystalline Materials. Adv. Mater. 2001, 13, 130–133. 10.1002/1521-4095(200101)13:2<130::AID-ADMA130>3.0.CO;2-L. [DOI] [Google Scholar]
  28. Che Y.; Yang X.; Balakrishnan K.; Zuo J.; Zang L. Highly Polarized and Self-Waveguided Emission from Single-Crystalline Organic Nanobelts. Chem. Mater. 2009, 21, 2930–2934. 10.1021/cm9007409. [DOI] [Google Scholar]
  29. Briseno A. L.; Mannsfeld S. C. B.; Reese C.; Hancock J. M.; Xiong Y.; Jenekhe S. A.; Bao Z.; Xia Y. Perylenediimide Nanowires and Their Use in Fabricating Field-Effect Transistors and Complementary Inverters. Nano Lett. 2007, 7, 2847–2853. 10.1021/nl071495u. [DOI] [PubMed] [Google Scholar]
  30. Krauss T. N.; Barrena E.; Zhang X. N.; de Oteyza D. G.; Major J.; Dehm V.; Würthner F.; Cavalcanti L. P.; Dosch H. Three-Dimensional Molecular Packing of Thin Organic Films of PTCDI-C8 Determined by Surface X-ray Diffraction. Langmuir 2008, 24, 12742–12744. 10.1021/la8030182. [DOI] [PubMed] [Google Scholar]
  31. Kubo R. The fluctuation-dissipation theorem. Rep. Prog. Phys. 1966, 29, 255–284. 10.1088/0034-4885/29/1/306. [DOI] [Google Scholar]

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