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Monolayer Field-Effect Transistors of Nonplanar Organic Semiconductors with Brickwork Arrangement Liang Shan, Danqing Liu, Hao Li, Xiaomin Xu, Bowen Shan, Jian-Bin Xu, and Qian Miao* Charge transport in organic semiconductors highly depends on the arrangement of semiconductor molecules in the solid state. One fundamental question regarding organic semiconductors for application in organic field-effect transistors (OFETs) is what kind of molecular packing motif can achieve higher field-effect mobility.[1] Most of the organic semiconductors that have been tested in OFETs to date have planar π-backbones, which are typically arranged in four packing motifs: i) herringbone packing without face-to-face π–π overlap between adjacent molecules; ii) herringbone packing with face-to-face π–π overlap between adjacent molecules; iii) 1D π-stacking with face-to-face π–π overlap; and iv) 2D π-stacking with a brickwork arrangement.[2] The packing motif of a particular planar π-backbone can be tuned by varying the substituents attached to it. One of the best examples of such tuning is provided by Anthony’s 6,13-bis((triisopropylsilyl)ethynyl)-pentacene, where the bulky triisopropylsilyl substituents direct 2D π-stacking of pentacene.[3] The molecular packing of nonplanar organic semiconductors remain largely unexplored although the curved π-faces can in principle adopt new intermolecular contacts typically unavailable to flat molecules.[4] Here we demonstrate that the molecular packing of twisted hexabenzoperylenes (HBPs) 1a-b[5] can be dramatically changed by extra substitution at the 5 and 10 positions. The HBP backbone in 1a-b and 2a-d is π-isoelectronic to the well-known planar hexa-peri-hexabenzocoronene (p-HBC) but forced out of plane by steric strains at the fjord regions as shown in Figure 1. The new HBPs 2a-d exhibit an unusual brickwork arrangement of the twisted π-faces, which leads to a π-stacked nanosheet sandwiched between two insulating layers of alkyl chains. As a consequence of this unprecedented molecular assembly, through a dip-coating process, 2b-d easily formed micrometer-sized one-molecule-thick nanosheets. Field-effect transistors were successfully fabricated on not only multilayer films but also monolayer nanosheets of 2b-d, suggesting that the self-assembled nanosheet herein is a new supramolecular approach to 2D materials. HBPs 2a-d were synthesized in a way similar to the synthesis of 1a reported by us[5] as detailed in the Supporting Information. L. Shan, Dr. D. Liu, X. Xu, B. Shan, Prof. Q. Miao Department of Chemistry The Chinese University of Hong Kong Shatin, New Territories, Hong Kong, China E-mail: [email protected] H. Li, Prof. J.-B. Xu Department of Electronic Engineering The Chinese University of Hong Kong Shatin, New Territories, Hong Kong, China

DOI: 10.1002/adma.201500149

Adv. Mater. 2015, DOI: 10.1002/adma.201500149

Orange solutions of 2a-d exhibited almost identical UV–vis absorption with the longest-wavelength absorption maximum at 512 nm as shown in Figure 2. To determine the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), the redox behaviors of 2a-d in solution were investigated with cyclic voltammetry. The cyclic voltammograms of 2a-d (Figure S2, Supporting Information) are essentially the same exhibiting one reversible reduction peak ca. −1.90 V and two quasi-reversible oxidation peaks at ca. 0.20 and 0.50 V versus ferrocenium/ferrocene. From these potentials, the HOMO and LUMO energy levels of 2a-d are estimated as −5.3 and −3.2 eV, respectively,[6] and the HOMO–LUMO gap is calculated as 2.1 eV, which is in accordance with the absorption edge at 565 nm (2.2 eV). Red single crystals of 2a and 2b grown from solutions in dichloromethane were qualified for X-ray crystallography.[7] The crystal structure reveals that 2a adopts a chiral twisted conformation (Figure 3a) similar to the less substituted HBP 1a, and its fjord regions are distorted with torsion angles of 43.9° and 41.2°. The crystal of 2a is racemic with a pair of enantiomers stacked in a brickwork arrangement, where each molecule of P-enantiomer (shown in yellow) is π-stacked with four adjacent molecules of M-enantiomer (shown in light blue) in a face-to-face orientation as shown in Figure 3a. As the polycyclic backbone of 2a can be regarded as two roughly planar benzotetracene subunits jointed by the twisted central benzene ring, the π-faces of 2a are stacked in two directions with a π-to-π distance of about 3.6 Å. This type of 2D π-stacking is very rare and only documented with a bay-chlorinated perylene tetracarboxylic diimide to the best of our knowledge.[8] In contrast, 1a crystallized with solvent molecules forming face-to-face π-stacked dimers, which are only contacted with edge-to-face aromatic interactions as shown in Figure 3b.[5] The existence of dichloromethane molecules in the crystal lattice suggests inefficient filling of space with molecules of 1a. The apparent different packing modes of 1a and 2a can be attributed to the two benzylic methyl groups of 2a, which presumably block the edge-to-face interactions between π-stacked dimers of 1a. The unique packing motif of 2a results in a single-molecule sheet with the benzylic methyl groups of the M- and P-enantiomers positioned on the opposite sides of the nanosheet as shown in Figure 4a,b. The crystal structure of 2b reveals essentially the same twisted conformation and brickwork arrangement as that of 2a as shown in Figure 4c. The propyl groups in 2b adopt a zigzag conformation and lead to a slightly thicker nanosheet without changing the brickwork arrangement. As a result, molecules of 2b are closely packed with π–π interactions along two dimensions within a nanosheet while the nanosheets are held together by weaker van der Waals

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Figure 1. Molecular structures of 1a-b and 2a-d.

interactions between propyl groups. Figure 4d shows the crystal lattice of 2b as viewed along the a axis and two neighboring nanosheets with interdigitation between the propyl groups. The thickness of one nanosheet in the crystal structures of 2a and 2b can be defined either by the positions of the hydrogen atoms on the opposite surfaces or by the d spacing of certain crystallographic planes. According to the distance between two least squares planes of the outermost hydrogen atoms (shown in Figure S3, Supporting Information), the nanosheets of 2a and 2b are 1.15 and 1.46 nm thick, respectively. According to the d spacing of the (010) plane, one nanosheet of 2a is 1.18 nm thick as shown in Figure 4b, and according to the d spacing of the (020) plane,[9] one nanosheet of 2b is 1.33 nm thick as shown in Figure 4d. The nanosheet of 2a has essentially the same thickness according to the two definitions, while the nanosheet thickness of 2b as defined by the surface hydrogen atoms is larger than the d spacing of the (020) plane by 0.13 nm due to the interdigitation between propyl groups. The crystal structure of 2b led to two hypotheses. First, attaching longer alkyl chains to the benzylic carbons of 2a would not change the brickwork arrangement, and thus 2c and 2d could also self-assemble into a π-stacked sheet that is sandwiched between two insulating layers of alkyl chains. Second, the nanosheets of 2a-d may be scaled down to a monolayer. To test these hypotheses, thin films of 2b-d that were tens of nm thick were prepared by dip coating and studied with UV–vis

Figure 2. Normalized UV–vis absorption of 2b-d in solutions (0.01 × 10−3 M in dichloromethane) and dip-coated thin films.

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Figure 3. Comparison of intermolecular contacts in the crystals of a) 2a and b) 1a (the M-enantiomers are shown in light blue and the P-enantiomers shown in yellow, the benzylic methyl in M- and P-enantiomers are shown in blue and orange, respectively, the hydrogen atoms are removed and carbon and oxygen atoms are shown as 50% probability ellipsoids).

absorption spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM). However, thin films of 2a could not be prepared by solution-based methods because of its low solubility. To avoid thermal isomerization of HBP,[5] all the dipcoating processes in this study, including removal of solvent residues in a vacuum, were conducted at room temperature. Thin films for UV–vis spectroscopy and XRD were prepared by immersing a glass substrate in a solution of 2b-d in dichloromethane or mixed dichloromethane and acetone and pulling it up with a constant speed of ca. 0.2 mm min−1. The longestwavelength absorption maxima of 2b-d in thin films occurs at 574 nm, which shifts to red by 62 nm relative to that of the solutions as shown in Figure 2. This red shift can be attributed to electronic delocalization between π-stacked molecules,[10,11] and is thus an indicator of strong π–π interactions, in agreement with the formation of π-stacked nanosheets. The X-ray diffraction from dip-coated films of 2b exhibits one intense diffraction peak at 2θ = 6.61° (d spacing of 1.33 nm) accompanied by a higher-order peak at 2θ = 13.25° (d spacing of 0.67 nm), in agreement with a film containing layers parallel to the surface. The d spacing of 1.33 nm is in accordance with the (020) diffraction as derived from the single crystal structure. Dip-coated films of 2c exhibit one X-ray diffraction peak at 2θ = 5.61° (d spacing of 1.57 nm), while those of 2d exhibit one intense diffraction at 2θ = 4.31° (d spacing of 2.05 nm) accompanied with a higher-order peak at 2θ = 8.59° (d spacing of 1.03 nm). These diffraction patterns suggest that the films of 2c and 2d have a layered structure with each layer of 1.57 and 2.05 nm thick, respectively. In order to form monolayer nanosheets, ultra-thin films of 2b-d were prepared by pulling an oxidized silicon substrate

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COMMUNICATION Figure 4. Nanosheets of 2a and 2b in the crystal structures: a) side view for a layer of π-stacked molecules of 2a; b) a layer of π-stacked molecules of 2a as viewed along the c axis of the crystal lattice; c) front view for a layer of π-stacked molecules of 2b; d) two layers of π-stacked molecules of 2b as viewed along the a axis of the crystal lattice. (In (a)–(c), the M-enantiomers are shown in light blue and the P-enantiomers are shown in yellow, the benzylic methyl and propyl groups in M- and P-enantiomers are shown in blue and orange, respectively; in (d), the hydrogen atoms are removed and carbon and oxygen atoms are shown as 50% probability ellipsoids).

from a solution of 2b-d in less volatile solvents, a 2:1 mixed solvent of toluene and dichloromethane for 2b or toluene for 2c and 2d because of lower solubility of 2b in toluene. It was found that a concentration of 1 to 2 mg mL−1 and a pulling speed of 2 to 20 mm min−1[12] were the optimum conditions for the formation of monolayers of 2b-d. This pulling speed is faster than that for dip-coating multilayer films by one to two orders of magnitude. A combination of a fast pulling speed with a less volatile solvent results in slow crystallization relative to pulling, which likely facilitates the formation of monolayers. It was found that a concentration higher than 2 mg mL−1 or a pulling speed lower than 2 mm min−1 resulted in a significant amount of multilayers, and the size of resulting monolayers roughly increased from about 1 µm to tens of micrometer or even over 100 µm as the pulling speed decreased from 20 to 2 mm min−1. As shown in Figure 5, the ultrathin film of 2b prepared at a pulling speed of 20 mm min−1 comprises micrometer-sized dendritic islands of monolayer nanosheets, which are about 1.4 nm thick. This thickness is in agreement with the values measured from the crystal structure of 2b. The ultrathin film of 2c prepared at a pulling speed of 16 mm min−1 comprises dendritic islands of monolayer nanosheets about 5 µm long. On the top of the first layer, the second and third layers of small area are also observed. The ultra-thin film of 2d prepared at a pulling speed of 2 mm min−1 contains dendritic monolayers about 70 µm long. As measured from AFM

Adv. Mater. 2015, DOI: 10.1002/adma.201500149

cross-section analysis, the nanosheets of 2c and 2d are about 1.7 and 2.5 nm thick, respectively. The nanosheet thickness of 2b-d as measured from AFM section analysis is generally slightly larger than the layer spacing as calculated from XRD of the corresponding multilayer films. Such a difference can be attributed to the interdigitation of alkyl chains between neighboring layers. The dendritic nanosheets of 2b-d appear birefringent when observed with a polarized-light microscope, and rotation of a bright domain by 45° under cross-polarized light led to extinction (Figure S15, Supporting Information). This suggests each domain is single crystalline. The general capability of 2b-d to form nanosheets suggests that the π-stacked nanosheet can have its two surfaces functionalized by different groups without changing brickwork arrangement of twisted HBPs. Unlike graphene, which has π-electrons above and below a one-atom-thick flat sheet of covalently-bonded sp2 carbon atoms, the monolayer nanosheets of 2b-d have 2D stacking of π-orbitals within the plane of nanosheet. By self-assembling into such an unprecedented nanostructure, twisted HBPs 2a-d differentiate themselves from structurally related planar p-HBCs and contorted hexa-cata-hexabenzocoronenes (c-HBCs), which organize into columnar liquid crystals,[4,13] crystalline nanocables,[14] or graphitic nanotubes[15,16] depending on the structure and number of flexible chains attached to the conjugated backbones. The 2D π-stacking in the nanosheets and the relatively high HOMO energy level (−5.3 eV) suggest that 2a-d are

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0.04 cm2 V−1 s−1 is extracted from this I–V curve using the equation: IDS = (µWCi/2L) (VG − VT)2, where IDS is the drain current, µ is field-effect mobility, Ci is 11 nF cm−2 as the capacitance per unit area for 300 nm-thick SiO2, W is the channel width, L is the channel length, and VG and VT are the gate and threshold voltage, respectively. As measured from 11 individual devices in air, the monolayer nanosheets of 2b-d all functioned as p-channel transistors with field-effect mobility of 0.035 ± 0.019 cm2 V−1 s−1, and the highest field-effect mobility of 0.076 cm2 V−1 s−1 was record from a monolayer FET of 2d. The variation of mobility and threshold voltage as detailed in Table S4, Supporting Information, can be attributed to varied quality of monolayers and contacts as a result of manual transfer of electrodes and poor control of crystallization in the dip-coating process. In comparison to the monolayer FETs of 2b-d, most of the earlier reported monolayer FETs with semiconductor molecules covalently bonded to the dielectrics required channel lengths of sub-micrometer to ensure gate voltage modulation of the source-to-drain current[19] and suffered low device yield and poor reproducibility due to defects and the limited intermolecular π–π coupling between the molecules in the self-assembled monolayers.[20–22] The field-effect mobility of the monolayer FETs of 2b-d is comparable to the best value (0.024 ± 0.007 cm2 V−1 s−1)[23] reported for the monolayer FETs with metal electrodes, but lower than the mobility of the reported monolayer FETs with graphene electrodes.[22] For comparison, conventional multilayer OFETs of 2b-d were also fabricated. Unlike the monolayer transistors on SiO2, the multilayer films of 2b-d were dip-coated on a thin layer of aluminum oxide and titanium [24] which was modified Figure 5. AFM images and section analysis of ultra-thin films of 2b-d on SiO2 showing oxide (AlOy/TiOx), with a self-assembled monolayer (SAM) of monolayer nanosheets. 12-methoxydodecylphosphonic acid.[25] The SAM-modified AlOy/TiOx was found a better dielectric surface promising candidates for p-type organic semiconductors. To test the semiconductor properties of the nanosheets, than SiO2 for fabrication of multilayer FETs of 2b-d leading top-contact field-effect transistors (FETs) of 2b-d were fabrito highly ordered films with higher field-effect mobility. Thin cated by mechanically transferring a thin layer of gold onto films of 2b-d were formed by immersing the substrate into a the monolayer nanosheets.[17,18] The conducting channels solution of 2b-d in mixed dichloromethane and acetone and then pulling it up with a speed of ca. 0.2 mm min−1, which in the resulting monolayer FETs were 10 to 35 µm long and 3 to 6 µm wide. Figure 6a shows the polarized light image for was much slower than that used in the dip-coating process to a typical monolayer transistor of 2d, where the conducting form monolayers. These films comprised of aligned crystalline channel is 30 µm long and 3 µm wide as measured from the fibers and were 40 to 100 nm thick by containing tens of layers narrowest region. The monolayer nanosheet is 2.4 nm thick of nanosheets. Vacuum-deposition of gold through a shadow as measured from the AFM section analysis (Figure S18, Supmask onto these dip-coated multilayer films led to transistor porting Information). Figure 6b shows transfer I–V curves for channels of 50 to 150 µm long and 1 to 2 mm wide. As measthis monolayer transistor as measured in air. A mobility of ured in air from these devices, 2b-d all functioned as p-type

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the Research Grants Council of Hong Kong (Project Nos. GRF402011 and GRF14303614). Received: January 12, 2015 Revised: March 12, 2015 Published online:

Figure 6. a) Reflection polarized light image of a monolayer FET of 2d. b) Drain current (IDS) versus gate voltage (VG) with drain voltage (VDS) at −40 V for the monolayer FET of 2d shown in (a).

semiconductors with field-effect mobilities of 0.099 ± 0.036, 0.15 ± 0.04, and 0.58 ± 0.11 cm2 V−1 s−1, respectively. These mobilities are higher than that of the less substituted HBP 1b by three orders of magnitude,[5] in agreement with the 2D π-stacking of 2b-d. The higher mobility of 2d is presumably related to its longer alkyl chains, which enhance the van der Waals interactions between nanosheets by interdigitation. The monolayer OFETs have lower mobility than the corresponding multilayer OFETs presumably because the monolayer is more vulnerable to traps and defects[21] that are produced by fabrication and from environment. In summary, the above study puts forth a new bottom-up supramolecular approach to semiconducting nanosheets from brickwork arrangement of nonplanar π-faces, which are roughly perpendicular to the sheet plane. Dip-coating 2b-d on silicon substrates resulted in one-molecule-thick nanosheets, whose size varied from 1 µm to over 100 µm depending on the pulling speed. OFETs fabricated on the monolayer nanosheets and the multilayer thin films of 2b-d exhibited hole mobility as high as 0.076 and 0.82 cm2 V−1 s−1, respectively. An OFET can in principle function as a sensor by converting a molecular interaction event into an electric signal when the organic semiconductors or the gate dielectrics are exposed to the analyte molecules and the adsorption of analyte molecules leads to a change of the channel conductivity.[26] With the charge transport channel directly exposed to environment, the monolayer OFETs of 2b-d in principle provide a promising platform for sensing applications. Covalently linking recognition sites to the end of the alkyl chains of 2b-d may lead to new semiconducting nanosheets as selective electrical sensors, which are currently in progress in our laboratory.

Supporting Information Supporting Information is available from the Wiley Online Library or from the author.

Acknowledgements The authors thank Hoi Shan Chan (the Chinese University of Hong Kong) for the single-crystal crystallography. This work was supported by

Adv. Mater. 2015, DOI: 10.1002/adma.201500149

[1] V. Coropceanu, J. Cornil, D. A. da Silva Filho, Y. Olivier, R. Silbey, J.-L. Bredas, Chem. Rev. 2007, 107, 926. [2] C. Wang, H. Dong, W. Hu, Y. Liu, D. Zhu, Chem. Rev. 2012, 112, 2208. [3] a) J. E. Anthony, J. S. Brooks, D. L. Eaton, S. R. Parkin, J. Am. Chem. Soc. 2001, 123, 9482; b) J. E. Anthony, D. L. Eaton, S. R. Parkin, Org. Lett. 2002, 4, 15. [4] S. Xiao, M. Myers, Q. Miao, S. Sanaur, K. Pang, M. Steigerwald, C. Nuckolls, Angew. Chem. 2005, 117, 7556; Angew. Chem. Int. Ed. 2005, 44, 7390. [5] J. Luo, X. Xu, R. Mao, Q. Miao, J. Am. Chem. Soc. 2012, 134, 13796. [6] The commonly used formal potential of the redox couple of ferrocenium/ferrocene (Fc+/Fc) in the Fermi scale is −5.1 eV, which is calculated on the basis of an approximation neglecting solvent effects using a work function of 4.46 eV for the normal hydrogen electrode (NHE) and an electrochemical potential of 0.64 V for (Fc+/Fc) versus NHE. C. M. Cardona, W. Li, A. E. Kaifer, D. Stockdale, G. C. Bazan, Adv. Mater. 2011, 23, 2367. [7] CCDC 1016756 and CCDC 1016757 contain the supplementary crystallographic data for 2a and 2b, respectively. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. [8] M. Gsänger, J. H. Oh, M. Könemann, H. W. Höffken, A.-M. Krause, Z. Bao, F. A. Würthner, Angew. Chem. 2010, 122, 752; Angew. Chem. Int. Ed. 2010, 49, 740. [9] Because the unit cell of 2b differs from that of 2a by containing four molecules rather than two molecules, the thickness of one nanosheet of 2b is defined by the crystallographic plane of (020) instead of (010). [10] Q. Miao, X. Chi, S. Xiao, R. Zeiss, M. Lefenfeld, C. Kloc, M. L. Steigerwald, T. Siegrist, C. Nuckolls, J. Am. Chem. Soc. 2006, 128, 1340. [11] S.-H. Lim, T. G. Bjorklund, F. C. Spano, J. C. Bardeen, Phys. Rev. Lett. 2004, 92, 107402. [12] L. Li, P. Gao, W. Wang, K. Müllen, H. Fuchs, L. Chi, Angew. Chem. 2013, 48, 12762; Angew. Chem. Int. Ed. 2013, 52, 12530. [13] A. Fechtenkötter, K. Saalwächter, M. A. Harbison, K. Müllen, H. W. Spiess, Angew. Chem. 1999, 111, 3224; Angew. Chem. Int. Ed. 1999, 38, 3039. [14] S. Xiao, J. Tang, T. Beetz, X. Guo, N. Tremblay, T. Siegrist, Y. Zhu, M. Steigerwald, C. Nuckolls, J. Am. Chem. Soc. 2006, 128, 10700. [15] J. P. Hill, W. Jin, A. Kosaka, T. Fukushima, H. Ichihara, T. Shimomura, K. Ito, T. Hashizume, N. Ishii, T. Aida, Science 2004, 304, 1481. [16] W. Jin, T. Fukushima, M. Niki, A. Kosaka, N. Ishii, T. Aida, Proc. Natl. Acad. Sci. USA 2005, 102, 10801. [17] Q. Tang, Y. Tong, H. Li, Z. Ji, W. Hu, Y. Liu, D. Zhu, Adv. Mater. 2008, 20, 1511. [18] X. Wang, J.-B. Xu, C. Wang, J. Du, W. Xie, Adv. Mater. 2011, 23, 2464. [19] H. Ma, O. Acton, D. O. Hutchins, N. Cernetic, A. K.-Y. Jen, Phys. Chem. Chem. Phys. 2012, 14, 14110. [20] M. Mottaghi, P. Lang, F. Rodriguez, A. Rumyantseva, A. Yassar, G. Horrowitz, S. T. Lenfan, D. Tondelier, D. Vuillaume, Adv. Funct. Mater. 2007, 17, 597.

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www.MaterialsViews.com [21] G. S. Tulevski, Q. Miao, M. Fukuto, R. Abram, B. Ocko, P. Pindak, C. Kagan, C. Nuckolls, J. Am. Chem. Soc. 2004, 126, 15048. [22] X. Guo, M. Myers, S. Xiao, M. Lefenfeld, R. Steiner, G. S. Tulevski, J. Tang, J. Baumert, F. Leibfarth, J. T. Yardley, M. L. Steigerwald, P. Kim, C. Nuckolls, Proc. Natl. Acad. Sci. USA 2006, 103, 11452. [23] E. C. P. Smits, S. G. J. Mathijssen, P. A. van Hal, S. Setayesh, T. C. T. Geuns, K. A. H. A. Mutsaers, E. Cantatore, H. J. Wondergem, O. Werzer, R. Resel, M. Kemerink, S. Kirchmeyer, A. M. Muzafarov,

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S. A. Ponomarenko, B. de Boer, P. W. M. Blom, D. M. de Leeuw, Nature 2008, 455, 956. [24] Y. Su, C. Wang, W. Xie, F. Xie, J. Chen, N. Zhao, J. Xu, ACS Appl. Mater. Interfaces 2011, 3, 4662. [25] D. Liu, X. Xu, Y. Su, Z. He, J. Xu, Q. Miao, Angew. Chem. 2013, 125, 6342; Angew. Chem. Int. Ed. 2013, 52, 6222. [26] J. T. Mabeck, G. G. Malliaras, Anal. Bioanal. Chem. 2006, 384, 343.

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Adv. Mater. 2015, DOI: 10.1002/adma.201500149

Monolayer Field-Effect Transistors of Nonplanar Organic Semiconductors with Brickwork Arrangement.

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