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Proceedings ArticleDOI: 10.1109/IWPSD.2007.4472577

F 4 CuPc based ambipolar organic thin-film transistors

01 Dec 2007-pp 563-564
Abstract: Ambipolar organic thin film transistors (OTFTs) based on a partially fluorinated copper phthalocyanine (F4CuPc) were fabricated and characterized We have demonstrated that the ambipolar charge transport is primarily dependent on the gate dielectric/ organic semiconductor interface

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Topics: Organic electronics (62%), Organic semiconductor (61%), Gate dielectric (60%) ...read more
References
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Journal ArticleDOI: 10.1038/NATURE03376
Lay-Lay Chua1, Lay-Lay Chua2, Jana Zaumseil2, Jui Fen Chang2  +5 moreInstitutions (2)
10 Mar 2005-Nature
Abstract: Organic semiconductors have been the subject of active research for over a decade now, with applications emerging in light-emitting displays and printable electronic circuits. One characteristic feature of these materials is the strong trapping of electrons but not holes1: organic field-effect transistors (FETs) typically show p-type, but not n-type, conduction even with the appropriate low-work-function electrodes, except for a few special high-electron-affinity2,3,4 or low-bandgap5 organic semiconductors. Here we demonstrate that the use of an appropriate hydroxyl-free gate dielectric—such as a divinyltetramethylsiloxane-bis(benzocyclobutene) derivative (BCB; ref. 6)—can yield n-channel FET conduction in most conjugated polymers. The FET electron mobilities thus obtained reveal that electrons are considerably more mobile in these materials than previously thought. Electron mobilities of the order of 10-3 to 10-2 cm2 V-1 s-1 have been measured in a number of polyfluorene copolymers and in a dialkyl-substituted poly(p-phenylenevinylene), all in the unaligned state. We further show that the reason why n-type behaviour has previously been so elusive is the trapping of electrons at the semiconductor–dielectric interface by hydroxyl groups, present in the form of silanols in the case of the commonly used SiO2 dielectric. These findings should therefore open up new opportunities for organic complementary metal-oxide semiconductor (CMOS) circuits, in which both p-type and n-type behaviours are harnessed.

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Topics: Organic semiconductor (58%), Polyfluorene (52%), Field effect (51%)

2,115 Citations


Journal ArticleDOI: 10.1126/SCIENCE.269.5230.1560
15 Sep 1995-Science
Abstract: Organic field-effect transistors have been developed that function as either n-channel or p-channel devices, depending on the gate bias. The two active materials are α-hexathienylene (α-6T) and C 60 . The characteristics of these devices depend mainly on the molecular orbital energy levels and transport properties of α-6T and C 60 . The observed effects are not unique to the two materials chosen and can be quite universal provided certain conditions are met. The device can be used as a building block to form low-cost, low-power complementary integrated circuits.

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Topics: Field-effect transistor (53%), Transistor (51%)

431 Citations


Open accessJournal ArticleDOI: 10.1063/1.365238
J. R. Ostrick1, J. R. Ostrick2, Ananth Dodabalapur, Luisa Torsi2  +7 moreInstitutions (3)
Abstract: Thin polycrystalline films of perylenetetracarboxylic dianyhydride (PTCDA), an organic molecular solid, exhibits substantial anisotropies in its electronic transport properties. Only electrons transport in the directions along molecular planes, while mainly holes transport in the direction normal to molecular planes. A series of measurements on both field effect transistors with PTCDA active layers and light emitting diodes with PTCDA transport layers documents the anisotropy seen in the electronic transport in thin films of PTCDA.

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  • FIG. 1. Room temperature PTCDA field-effect transistor drain current as a function of drain-source voltage for a series of gate voltages. Positive gate voltages induce electrons in the channel resulting in an increase of the drain current with gate voltage. In the inset is shown the schematic structure of the field-effect transistors.
    FIG. 1. Room temperature PTCDA field-effect transistor drain current as a function of drain-source voltage for a series of gate voltages. Positive gate voltages induce electrons in the channel resulting in an increase of the drain current with gate voltage. In the inset is shown the schematic structure of the field-effect transistors.
  • FIG. 2. ~a! Layer structure and electroluminescence spectrum of an Alq~60 nm! TAD ~60 nm! LED. The emitted light originates from the Alq and is observed through the glass.~b! In this structure, a 50 nm PTCDA layer is placed between the TAD and Alq. The observed emitted light~solid line! still originates from the Alq but the spectrum is modified by partial absorption in the PTCDA layer. Also shown~dotted line! is the calculated spectrum. It will be easily recognized that for Alq to emit light in this structure, holes must be transported through the PTCDA.~c! Similar device structure as~b! but with 100 nm of PTCDA.~d! This LED has two Alq layers, one on each side of the PTCDA layer. The emission spectrum is identical to that of device~c!.
    FIG. 2. ~a! Layer structure and electroluminescence spectrum of an Alq~60 nm! TAD ~60 nm! LED. The emitted light originates from the Alq and is observed through the glass.~b! In this structure, a 50 nm PTCDA layer is placed between the TAD and Alq. The observed emitted light~solid line! still originates from the Alq but the spectrum is modified by partial absorption in the PTCDA layer. Also shown~dotted line! is the calculated spectrum. It will be easily recognized that for Alq to emit light in this structure, holes must be transported through the PTCDA.~c! Similar device structure as~b! but with 100 nm of PTCDA.~d! This LED has two Alq layers, one on each side of the PTCDA layer. The emission spectrum is identical to that of device~c!.
  • FIG. 4. X-ray diffraction data from the FET structure, LED structure~without Alq and the Al cathode!, and PTCDA powder. Both the FET and LED structures have an intensity peak at the~102! plane indicating the PTCDA is parallel to the substrate. The intensity peaks designated as A and B are due to the polycrystalline ITO.
    FIG. 4. X-ray diffraction data from the FET structure, LED structure~without Alq and the Al cathode!, and PTCDA powder. Both the FET and LED structures have an intensity peak at the~102! plane indicating the PTCDA is parallel to the substrate. The intensity peaks designated as A and B are due to the polycrystalline ITO.
  • FIG. 3. The absorption and photoluminescence spectra of PTCDA.
    FIG. 3. The absorption and photoluminescence spectra of PTCDA.
Topics: Molecular solid (52%), Anisotropy (51%), Electron mobility (50%)

155 Citations


Journal ArticleDOI: 10.1016/S0039-6028(02)01967-2
01 Sep 2002-Surface Science
Abstract: We present a study of the organic semiconductor copper tetrafluorophthalocyanine (CuPCF4) on single crystalline Au(1 0 0) using photoemission spectroscopy and compare the results to the unsubstituated copper phthalocyanine (CuPC) complex, which is a well-established molecular organic semiconductor. The observed satellite structures in the C 1s core level photoemission spectra are discussed in detail and we show that the fluorination considerably changes the ionization potential while leaving the energy separation of the occupied electronic levels almost unchanged. Concerning the metal/organic interface, we observe the formation of an interface dipole, whereas the observed dipole is very different for CuPCF4 (0.6 eV) and CuPC (1.2 eV). Furthermore, the energy position of the highest occupied molecular orbital with respect to the gold Femi level is similar in both cases.

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Topics: Photoemission spectroscopy (54%), Organic semiconductor (54%), HOMO/LUMO (53%) ...read more

115 Citations