| 1. |
- Abdollahi Sani, Negar, et al.
(författare)
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All-printed diode operating at 1.6 GHz
- 2014
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 111:33, s. 11943-11948
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Tidskriftsartikel (refereegranskat)abstract
- Printed electronics are considered for wireless electronic tags and sensors within the future Internet-of-things (IoT) concept. As a consequence of the low charge carrier mobility of present printable organic and inorganic semiconductors, the operational frequency of printed rectifiers is not high enough to enable direct communication and powering between mobile phones and printed e-tags. Here, we report an all-printed diode operating up to 1.6 GHz. The device, based on two stacked layers of Si and NbSi2 particles, is manufactured on a flexible substrate at low temperature and in ambient atmosphere. The high charge carrier mobility of the Si microparticles allows device operation to occur in the charge injection-limited regime. The asymmetry of the oxide layers in the resulting device stack leads to rectification of tunneling current. Printed diodes were combined with antennas and electrochromic displays to form an all-printed e-tag. The harvested signal from a Global System for Mobile Communications mobile phone was used to update the display. Our findings demonstrate a new communication pathway for printed electronics within IoT applications.
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| 2. |
- Blaudeck, Thomas, et al.
(författare)
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Simplified Large-Area Manufacturing of Organic Electrochemical Transistors Combining Printing and a Self-Aligning Laser Ablation Step
- 2012
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Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlag Berlin. - 1616-301X .- 1616-3028. ; 22:14, s. 2939-2948
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Tidskriftsartikel (refereegranskat)abstract
- A hybrid manufacturing approach for organic electrochemical transistors (OECTs) on flexible substrates is reported. The technology is based on conventional and digital printing (screen and inkjet printing), laser processing, and post-press technologies. A careful selection of the conductive, dielectric, and semiconductor materials with respect to their optical properties enables a self-aligning pattern formation which results in a significant reduction of the usual registration problems during manufacturing. For the prototype OECTs, based on this technology, on/off ratios up to 600 and switching times of 100 milliseconds at gate voltages in the range of 1 V were obtained.
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| 3. |
- Israr, Muhammad Qadir, et al.
(författare)
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Structural characterization and biocompatible applications of graphene nanosheets for miniaturization of potentiometric cholesterol biosensor
- 2011
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Ingår i: Journal of Biosensors & Bioelectronics. - : OMICS Publishing Group. - 2155-6210. ; 2:3
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Tidskriftsartikel (refereegranskat)abstract
- The potentiometric cholesterol biosensor based on graphene nanosheets has been successfully miniaturized. Cholesterol oxidase (ChOx) has been immobilized onto graphene nanosheets exfoliated on copper wire through the process of physical adsorption,. The presented potentiometric biosensor renders effective selectivity and sensitivity (~82 mV/decade) for the detection of cholesterol biomolecules in 1 × 10−6 M to 1 × 10−3 M logarithmic range and quick output response within ~ 4 sec. The stability and reusability of the biosensor has also been investigated for the above mentioned range of cholesterol concentrations. The enzyme activity measurements on graphene nanosheets are studied using UV-Visible and FTIR spectrophotometers. Additionally, the functioning of the presented biosensor is studied for a range of temperatures (15-70 °C) and pH values (4-9).
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| 4. |
- Kawahara, Jun, et al.
(författare)
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Improving the color switch contrast in PEDOT:PSS-based electrochromic displays
- 2012
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Ingår i: Organic electronics. - : Elsevier BV. - 1566-1199 .- 1878-5530. ; 13:3, s. 469-474
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Tidskriftsartikel (refereegranskat)abstract
- Poly(3,4-ethylenedioxythiophene) chemically doped with poly(styrene sulfonic acid) (PEDOT:PSS) is a material system commonly used as a conductive and transparent coating in several important electronic applications. The material is also electrochemically active and exhibits electrochromic (EC) properties making it suitable as the active element in EC display applications. In this work uniformly coated PEDOT:PSS layers were used both as the pixel electrode and as the counter electrode in EC display components. The pixel and counter electrodes were separated by a whitish opaque and water-based polyelectrolyte and the thicknesses of the two EC layers were varied independently in order to optimize the color contrast of the display element. A color contrast (ΔE∗, CIE L∗a∗b∗ color space) exceeding 40 was obtained with maintained relatively short switching time at an operational voltage less than 2V.
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| 5. |
- Laiho, Ari, et al.
(författare)
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Amphiphilic Poly(3-hexylthiophene)-Based Semiconducting Copolymers for Printing of Polyelectrolyte-Gated Organic Field-Effect Transistors
- 2013
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 46:11, s. 4548-4557
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Tidskriftsartikel (refereegranskat)abstract
- Polyelectrolytes are promising electronically insulating layers for low-voltage organic field effect transistors. However, the polyelectrolyte–semiconductor interface is difficult to manufacture due to challenges in wettability. We introduce an amphiphilic semiconducting copolymer which, when spread as a thin film, can change its surface from hydrophobic to hydrophilic upon exposure to water. This peculiar wettability is exploited in the fabrication of polyelectrolyte-gated field-effect transistors operating below 0.5 V. The prepared amphiphilic semiconducting copolymer is based on a hydrophobic regioregular poly(3-hexylthiophene) (P3HT) covalently linked to a hydrophilic poly(sulfonated)-based random block. Such a copolymer is obtained in a three-step strategy combining Grignard metathesis (GRIM), atom transfer radical polymerization (ATRP) processes, and a postmodification method. The structure of the diblock copolymer was characterized using FT-IR, 1H NMR spectroscopy, and gel permeation chromatography (GPC).
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| 6. |
- Liu, Jiang, et al.
(författare)
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Double-Gate Light-Emitting Electrochemical Transistor: Confining the Organic p-n Junction
- 2013
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society. - 0002-7863 .- 1520-5126. ; 135:33, s. 12224-12227
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Tidskriftsartikel (refereegranskat)abstract
- In conventional light-emitting electrochemical cells (LECs), an off-centered p-n junction is one of the major drawbacks, as it leads to exciton quenching at one of the charge-injecting electrodes and results in performance instability. To combat this problem, we have developed a new device configuration, the double-gate light-emitting electrochemical transistor (DG-LECT), in which the location of the light-emitting p-n junction can be precisely defined via the position of the two gate terminals. Based on a planar LEC structure, two gate electrodes made from an electrochemically active conducting polymer are employed to predefine the p- and n-doped area of the light-emitting polymer. Thus, a p-n junction is formed in between the p-doped and n-doped regions. We demonstrate a homogeneous and centered p-n junction as well as other predefined junction patterns in these DG-LECT devices. Additionally, we report an electrical model that explains the operation of the DG-LECTs. The DG-LECT device provides a new tool to study the fundamental physics of LECs, as it dissects the key working process of LEC into decoupled p-doping, n-doping, and electroluminescence.
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| 7. |
- Liu, Jiang
(författare)
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Light-Emitting Electrochemical Transistors
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Since the discovery of conductive polymers in 1977, the implementation of organic conjugated materials in electronic applications has been of great interest in both industry and academia. The goal of organic electronics is to realize large-area, inexpensive and mechanically-flexible electronic applications.Organic light emitting diodes (OLEDs), as the first commercial product made from organic conjugated polymers, have successfully demonstrated that organic electronics can make possible a new generation of modern electronics. However, OLEDs are highly sensitive to materials selection and requires a complicated fabrication process. As a result, OLEDs are expensive to fabricate and are not suitable for low-cost printing or roll-to-roll process.This thesis studies an alternative to OLEDs: light-emitting electrochemical cells (LECs). The active materials in an LEC consist of a conjugated light-emitting polymer (LEP) and an electrolyte. Taking advantage of electrochemical doping of the LEP, an LEC features an in-situ formed emissive organic p-n junction which is easy to fabricate. We aim to control the electrochemical doping profile by employing a “gate” terminal on top of a conventional LEC, forming a lightemitting electrochemical transistor (LECT). We developed three generations of LECTs, in which the position of the light-emitting profile can be modified by the voltage applied at the gate electrode, as well as the geometry of the gate materials. Thus, one can use this structure to achieve a centered light-emitting zone to maximize the power-conversion efficiency. Alternatively, LECTs can be used for information display in a highly integrated system, as it combines the simultaneous modulation of photons and electrons.In addition, we use multiple LECs to construct reconfigurable circuits, based on the reversible electrochemical doping. We demonstrate an LEC-array where several different circuits can be created by forming diodes with different polarity at different locations. The thereby formed circuitry can be erased and turned into circuitry with other functionality. For example, the diodes of a digital AND gate can be re-programmed to form an analogue voltage limiter. These reprogrammable circuits are promising for fully-printed and large-area reconfigurable circuits with facile fabrication.
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| 8. |
- Liu, Jiang, et al.
(författare)
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Organic Reprogrammable Circuits Based on Electrochemically-Formed Diodes
- 2014
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 6:15, s. 13266-13270
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Tidskriftsartikel (refereegranskat)abstract
- To simplify the integration of organic electronics, we demonstrate a method for constructing reprogrammable circuits based on organic diodes. The organic p‐n junction diodes consisting of an organic polymers poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene and an electrolyte were formed by electrochemical doping at 70 °C, and stabilized at ‐30 °C. The reversible electrochemical reaction allows for the in‐situ change of the polarity of the organic p‐n junction. By forming diodes with different polarity at different locations, several circuits can be created, such as, logic gates, voltage limiter and AC/DC converter. The as‐made circuitry can be erased and turned into circuitry with other functionality. For example, the diodes of an AND gate can be re‐programmed to form an OR gate. The reprogrammable circuits contain merely two core layers, electrodes and active material, which is promising for large‐area and fully‐printed reconfigurable circuits with facile fabrication.
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| 9. |
- Liu, Jiang, et al.
(författare)
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Spatial Control of p-n Junction in an Organic Light-Emitting Electrochemical Transistor
- 2012
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society. - 0002-7863 .- 1520-5126. ; 134:2, s. 901-904
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Tidskriftsartikel (refereegranskat)abstract
- Low-voltage-operating organic electrochemical light-emitting cells (LECs) and transistors (OECTs) can be realized in robust device architectures, thus enabling easy manufacturing of light sources using printing tools. In an LEC, the p-n junction, located within the organic semiconductor channel, constitutes the active light-emitting element. It is established and fixated through electrochemical p- and n-doping, which are governed by charge injection from the anode and cathode, respectively. In an OECT, the electrochemical doping level along the organic semiconducting channel is controlled via the gate electrode. Here we report the merger of these two devices: the light-emitting electrochemical transistor, in which the location of the emitting p-n junction and the current level between the anode and cathode are modulated via a gate electrode. Light emission occurs at 4 V, and the emission zone can be repeatedly moved back and forth within an interelectrode gap of 500 mu m by application of a 4 V gate bias. In transistor operation, the estimated on/off ratio ranges from 10 to 100 with a gate threshold voltage of -2.3 V and transconductance value between 1.4 and 3 mu S. This device structure opens for new experiments tunable light sources and LECs with added electronic functionality.
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| 10. |
- Liu, Jiang, et al.
(författare)
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Vertical polyelectrolyte-gated organic field-effect transistors
- 2010
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Ingår i: Applied Physics Letters. - : American Institute of Physics. - 0003-6951 .- 1077-3118. ; 97, s. 103303-
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Tidskriftsartikel (refereegranskat)abstract
- Short-channel, vertically structured organic transistors with a polyelectrolyte as gate insulator are demonstrated. The devices are fabricated using low-resolution, self-aligned, and mask-free photolithography. Owing to the use of a polyelectrolyte, our vertical electrolyte-gated organic field-effect transistors (VEGOFETs), with channel lengths of 2.2 and 0.7 μm, operate at voltages below one volt. The VEGOFETs show clear saturation and switch on and off in 200 μs. A vertical geometry to achieve short-transistor channels and the use of an electrolyte makes these transistors promising candidates for printed logics and drivers with low operating voltage.
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