Analysing the TIPSP‐based VOFET through transistor efficiency ( g m /I D )
01 Mar 2019-Iet Circuits Devices & Systems (The Institution of Engineering and Technology)-Vol. 13, Iss: 2, pp 139-144
TL;DR: A simple vertical organic field-effect transistor (VOFET) structure has been fabricated using ambipolar 6, 13-bis (triisopropylsilyl ethynyl) pentacene (TIPSP) with a channel length of 90 nm, for the first time the authors are using transistor efficiency to extract VOFET's parameters.
Abstract: A simple vertical organic field-effect transistor (VOFET) structure has been fabricated using ambipolar 6, 13-bis (triisopropylsilyl ethynyl) pentacene (TIPSP) with a channel length (L) of 90 nm. This device can operate at –2 V which is much lower than the voltage, reported so far for the organic devices based on TIPSP. The first time, the authors are using transistor efficiency to extract VOFET's parameters. The threshold voltage (V th) of the device has been found to vary between 0.18 and 0.38 V with the current on/off ratio (I on /I off) of 104. The mobility (µ) of the device has been calculated as 0.62 cm2/Vs. The sub-threshold slope, transconductance (gm ), output conductance (g d), and early voltage (V E) have been found to be 140 ± 30 mV/decade, 2 µS, 10−6 S, and 1.3 ± 2 V, respectively.
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23 Apr 2019
TL;DR: A vertical resonant tunneling (RT) field effect transistor (VRTFET) fabricated using perovskite (CH3NH3PbI3) has been analyzed for sequential sharp negative differential resistance (NDR) peaks useful in multiple-valued logic devices.
Abstract: A vertical resonant tunneling (RT) field effect transistor (VRTFET), fabricated using perovskite (CH3NH3PbI3), has been analyzed for sequential sharp negative differential resistance (NDR) peaks useful in multiple-valued logic devices. NDR peaks are attributed to the sub-bands formation within the parabolic shaped band gap, present at the channel and drain/source interface due to Schottky barriers. Ambipolar CH3NH3PbI3 imparts both p and n mode characteristics with RT NDR peaks. An unprecedentedly high (100 to 1000 V–1) curvature coefficient (ϒ) has been found with two NDR peaks at a short interval, whose positions shift left, with gate bias. Due to the ionic nature of CH3NH3PbI3, hysteresis has also been observed in the transfer characteristics. This structure can overcome the limit of 60 mV/decade as well as a curvature limit of 40 V–1, important parameters for analog and digital applications. So, these devices promise cheaper and easy fabrication at commercial scale operation at ultralow voltage and lo...
4 citations
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TL;DR: In this paper, the state-of-the-art in organic field effect transistors (OFETs) are reviewed in light of requirements for demanding future applications, in particular active-matrix addressing for flexible organic light-emitting diode (OLED) displays.
Abstract: Over the past 25 years, organic field-effect transistors (OFETs) have witnessed impressive improvements in materials performance by 3–4 orders of magnitude, and many of the key materials discoveries have been published in Advanced Materials. This includes some of the most recent demonstrations of organic field-effect transistors with performance that clearly exceeds that of benchmark amorphous silicon-based devices. In this article, state-of-the-art in OFETs are reviewed in light of requirements for demanding future applications, in particular active-matrix addressing for flexible organic light-emitting diode (OLED) displays. An overview is provided over both small molecule and conjugated polymer materials for which field-effect mobilities exceeding > 1 cm2 V–1 s–1 have been reported. Current understanding is also reviewed of their charge transport physics that allows reaching such unexpectedly high mobilities in these weakly van der Waals bonded and structurally comparatively disordered materials with a view towards understanding the potential for further improvement in performance in the future.
1,992 citations
TL;DR: In this article, a thin film of a semiconducting polymer sandwiched between two electrodes, with the third electrode embedded within the semiconductor, plays a role similar to that of the grid in a vacuum tube.
Abstract: THE transistor, in its various forms, is a three-terminal amplifying electronic device1. Transistors are usually based on inorganic semiconductors, such as silicon or gallium arsenide1, but there is increasing interest in the use of organic semiconductors2–1, motivated by their structural flexibility and tunable electronic properties. The organic transistors fabricated to date have used a conventional 'field-effect' architecture; unfortunately, such devices involve relatively long conduction pathways which, owing to the low carrier mobilities of the organic materials, render them inherently slow. In an attempt to circumvent this problem, we have developed a different device geometry, more closely related to that of the vacuum-tube triode. The structure consists of a thin film of a semiconducting polymer sandwiched between two electrodes, with the third electrode―a layer of a porous metallic polymer5― embedded within the semiconductor. The third electrode plays a role similar to that of the grid in a vacuum tube, controlling the current flow between the two outermost electrodes. This thin-film architecture reduces the length of the conduction pathway, resulting in a relatively fast response time and, in contrast to conventional field-effect transistors, does not require lateral patterning.
333 citations
TL;DR: In this paper, p-type doping of hole-transport organic molecular material N,N′-diphenyl-N,N, N′-bis(1-naphthyl)-1,1′-biphensyl-4,4-diamine (α-NPD) with tetrafluorotetracyanoquinodimethane (F4-TCNQ) using direct and inverse photoemission spectroscopy, contact potential difference measurements, and in situ currentvoltage (I-V) measurements
Abstract: We investigate p-type doping of the hole-transport organic molecular material N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) with tetrafluorotetracyanoquinodimethane (F4-TCNQ) using direct and inverse photoemission spectroscopy, contact potential difference measurements, and in situ current–voltage (I–V) measurements. The close match between the ionization energy of α-NPD and the electron affinity of F4-TCNQ leads to an efficient charge transfer between highest occupied molecular orbital of the host and lowest occupied molecular orbital of the dopant. The Fermi level moves down towards the valence states by 0.62 eV in the 0.5% doped film with respect to the undoped film, and a narrow space charge layer (∼60 A) forms at the interface with Au. Hole injection in the doped devices increases by several orders of magnitude due to tunneling through the depletion region. The large relaxation energy of the ionized α-NPD molecule limits the movement of the Fermi level and, ultimately, the hol...
296 citations
TL;DR: In this paper, the authors demonstrate tuning of hole injection barriers in bottom contact triisopropylsilylethynyl pentacene (TIPS-pentacene) organic thin film transistors (OTFTs).
Abstract: We demonstrate tuning of hole injection barriers in bottom contact triisopropylsilylethynyl pentacene (TIPS-pentacene) organic thin film transistors (OTFTs) by forming the self-assembled monolayers (SAMs) of thiophenol, 4-fluorothiophenol, or pentafluorothiophenol on the pristine Ag electrode. The work functions of SAM-treated Ag electrodes are measured by Kelvin probe method. The TIPS-pentacene OTFT devices were fabricated by a drop-cast method with a micropipette like an inkjet printing. The OTFTs with pentafluorothiophenol-Ag electrodes as source and drain exhibit carrier mobility of 0.17cm2∕Vs and on/off current ratio of 105 because of almost no hole injection barrier to TIPS pentacenes. The SAM-treated Ag electrodes are robust over repeated electrical scans of 100cycles.
240 citations