Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session S50: Organic Electronics III: Organic Transistors and SensorsFocus
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Sponsoring Units: DPOLY DMP Chair: Xiaodan Gu, University of Southern Mississippi Room: BCEC 252B |
Thursday, March 7, 2019 11:15AM - 11:27AM |
S50.00001: Y-shape DNA guided Ni ion chain based nanowire transistor development and characterization Chia-Ching Chang, Wen-Hung Wang, Wen-Bin Jian, Yu-Chang Chen Recently studies indicate that DNA template guided Ni ion chain (Ni-DNA) is a conducting nanowire and it possesses multi-states memory effect owing to the Ni ions redox state transition by external bias. By designing the sequences of DNA, Y-shape Ni-DNA molecules have been synthesized and characterized. Furthermore, these unique Ni-DNA molecules were linked with three-terminal nanodevice via self-assembly process. The negative differential resistance behavior of I-V curves can be observed between each two terminals of device. By assigning these three terminals as source, drain and gate terminal and the source-drain currents can be regulated by different gate voltage. This is the first Ni-DNA nanowire based transistor has be developed in the world. |
Thursday, March 7, 2019 11:27AM - 11:39AM |
S50.00002: Influence of self-assembled monolayers on electronic properties of poly(3-hexylthiophene) at the polymer/substrate interface Jill Wenderott, Peter Green The impact of self-assembled monolayers (SAMs) on electronic properties of poly(3-hexylthiopene) (P3HT) thin films, of different morphologies, at P3HT/substrate interfaces is reported. The SAMs, trichloro(1H,1H,2H,2H-perfluorooctyl)silane (FTS) and octadecyltrichlorosilane (OTS), modified the surface energy and work function (WF) of indium tin oxide substrates, which influenced charge transfer and band bending behavior of P3HT films at the polymer/substrate interface. This band bending behavior could not be explained solely in terms of substrate WF modification. Investigations of P3HT films fabricated via matrix-assisted pulsed laser evaporation (MAPLE) and spin-casting revealed that the degrees of band bending and breadths of densities of states were associated with changes to electronic structure, strongly affected by the morphological structures of films. The morphological structures of films were influenced by film fabrication method and surface energies of the substrates. The implications of our findings are that the electronic properties of the system are influenced by the WFs and surface energies of SAM-modified substrates and the morphologies of thin P3HT films.1 |
Thursday, March 7, 2019 11:39AM - 11:51AM |
S50.00003: Enhanced Charge Injection Properties of Organic Field Effect Transistor via Molecular Implantation Doping Youngrok Kim, Seungjun Chung, Kyungjune Cho, David Harkin, Wang-Taek Hwang, Daekyoung Yoo, Jae-Keun Kim, Woocheol Lee, Younggul Song, Heebeom Ahn, Yongtaek Hong, Henning Sirringhaus, Keehoon Kang, Takhee Lee Organic semiconductors (OSCs) have been widely studied due to their merits such as mechanical flexibility, solution processability, and large-area fabrication. However, because of the Schottky contact at the metal/OSC interfaces, a non-ideal transfer curve feature often appears in the low drain voltage region. Here, we demonstrated a selective contact doping of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) by solid-state diffusion in poly 2,5-bis(3-hexadecylthiophen-2-yl) thieno [3,2-b] thiophene (PBTTT) to enhance carrier injection in bottom-gate PBTTT organic field effect transistors (OFETs). This doping exhibited a high conductivity with favorable charge transport properties [1]. Furthermore, we investigated the effect of post-doping treatment on diffusion of F4-TCNQ molecules in order to improve the device stability. In addition, the application of the doping technique to the low-voltage operation of PBTTT OFETs with high-k gate dielectrics demonstrated a potential for designing scalable and low-power organic electronic devices by utilizing doping of conjugated polymers. |
Thursday, March 7, 2019 11:51AM - 12:27PM |
S50.00004: Contacts in Organic Field-Effect Transistors Invited Speaker: Oana Jurchescu Organic semiconductors are versatile materials for emerging low-cost, lightweight, flexible devices, but their incorporation in consumer applications is delayed by inadequate performance. Inefficient charge injection at the electrode/semiconductor interface represents a significant hurdle in the pursuit of the promised potential of organic semiconductors. Moreover, with increasing the effective mobility of organic semiconductor layer and reducing the channel dimensions, this problem becomes even more prevalent. In this talk, I will focus on describing the origin and characterization of contact effects in organic field-effect transistors and their impact on device performance and accuracy in extraction of charge carrier mobility. Several types of manifestations of contact effects will be presented, as well as their impact on the device characterization. I will discuss methods for reducing contact resistance and will emphasize on a simple strategy consisting of developing high workfunction surface domains at the surface of the injecting electrodes to promote channels of enhanced injection [1]. This led to contact resistances of 200 Ωcm and device charge carrier mobilities of 20 cm2/Vs independent of the applied gate voltage. The proposed approach is efficient for both small molecule and polymeric thin-film transistor devices, and can be generally applied in all common processes and device architectures. In addition to allowing the demonstration of high-mobility transistors with near ideal current-voltage characteristics, the use of this method leads to accurate measurement of the charge carrier mobility, a critical step in a rational material design. |
Thursday, March 7, 2019 12:27PM - 12:39PM |
S50.00005: Limits to Charge Carrier Motion in High-Performance Organic Semiconductors: Role of Energy Barriers at Grain Boundaries and Interface Traps Ilja Vladimirov, Michael Kühn, Thomas Gessner, Falk May, Ralf Weitz Using our recently developed surface-crystallization method [1], we have realized 3 – 10 nm thin, highly-crystalline thin films or a novel perylene diimide and investigated temperature-dependent charge transport. Via a combination of as-measured density-of-states with Kinetic Monte Carlo simulations [2], we present strong hints that it is rather the energetic barriers at grain boundaries than the usually identified energetic traps that limit charge carrier motion below room temperature. We furthermore have observed that above room temperature the charge carrier mobility decreases upon increasing the charge carrier density in the semiconducting film [3]. While the true cause for this suppression is currently unclear, we present evidence that the squeezing of charges closer to the semiconductor/dielectric by the gate dielectric field a subsequent scattering at this interface might cause the drop in mobility. We believe that our combined observations will help to understand the still debated nature of charge transport in high-quality organic semiconductors. |
Thursday, March 7, 2019 12:39PM - 12:51PM |
S50.00006: Impact of Mixed Phases and Domain Network Tortuosity on Long-Range Charge Transport in Phase-Separated Organic Semiconductor Blends Michael Heiber, Andrew Herzing, Lee Richter, Dean DeLongchamp Quantitative structure-property models for how the molecular-scale and meso-scale structure in polymer blends affect long-range charge transport behavior is needed to refine design rules for a wide variety of organic electronic device applications, such as photovoltaics, field-effect transistors, thermoelectrics, and bioelectronics. In this presentation, we will demonstrate the use of kinetic Monte Carlo simulations with morphologies derived from electron tomography measurements and a simple Ising-based model to probe how the multi-length-scale structure due to disordered interfacial mixed phases and mesoscale domain network tortuosity impact long-range charge transport phenomena. We will specifically quantify how these features impact the electric field and temperature dependence of the charge carrier mobility. |
Thursday, March 7, 2019 12:51PM - 1:03PM |
S50.00007: Controlling the Doping Mechanism in Thin Film Transistors Through Design of Polymeric Ionic Liquid Gate Dielectrics Dakota Rawlings, Elayne Thomas, Michael L. Chabinyc, Rachel Segalman Two disparate modes of operation can occur when gating an organic thin film transistor (OTFT) with an electrolyte. Field-effect (FE) doping occurs when the semiconductor is impermeable to ions, whereas electrochemical (EC) doping of the bulk occurs when the active layer is permeable to ions. Here, we present a method to control the mode of charge accumulation in an OTFT with a constant semiconducting layer by gating with polymeric ionic liquids (PILs) of opposite polarity. Ion infiltration into the active layer is driven by attraction between ions and electronic carriers of opposite charge. As a result, tethering either the anion or the cation to a polymer backbone in the dielectric enables a direct comparison between FE and EC doping. Two PILs of opposite polarity have been synthesized and employed as the dielectric in p-type OTFTs. Tethering either the anion or the cation is shown to dictate whether ions infiltrate the active layer. Interfacial FE doping decreases the accumulation layer thickness and increases the carrier concentration as a function of injected charge. The local carrier concentration in the accumulation layer is found to be the main factor effecting the threshold voltage and the conductivity of the devices, despite the difference in doping mechanisms. |
Thursday, March 7, 2019 1:03PM - 1:15PM |
S50.00008: Hysteresis and Gate Bias Stress Effects in Organic Electrochemical Transistors based on Room Temperature Ionic Liquids Vikash Kaphle, Shiyi Liu, Chang Min Keum, Bjorn Lussem Organic Electrochemical Transistors (OECTs) transduce ionic into electronic signals. The transconductance of OECTs is in the mS range and outperforms other traditional and emerging transistors.[1] Here, we show that the transconductance of OECTs is limited by a voltage dependent contact resistance at the source/drain electrodes.[2] By an optimization of the device geometry and by using a mixture of room temperature ionic liquid (C2MIM EtSo4) and PBS as an electrolyte, we reach a transconductance greater than 2 mS. For later applications of OECTs, the stability of these devices is of utmost importance. We investigate the origin of a hysteresis observed in the transfer characteristic and the origin of gate bias stress effects. We propose that these instabilities are caused by ions moving slowly inside the electrolyte and the semiconductor, leading to a different time constant and hence reversible gate stress bias effects. We discuss several approaches to minimize these instabilities.[3] |
Thursday, March 7, 2019 1:15PM - 1:27PM |
S50.00009: Chemical Doping Efficiency by Semiconducting Polymer Type in Electrolyte-gated Polymer Transistor Seung Hoon Oh, Jiyoul Lee We report the characterization of chemical doping process with electrolyte-gated polymer transistors (EGT), where classical highly crystallined semiconducting polymer - PBTTT or amorphous donor-acceptor (D-A) type semiconducting copolymer -DPP-2T-TT was used as the active layer and an ion gel comprising a polymer network swollen with an ionic liquid was used as the electrolyte. Gate-bias dependent doping concentration that is extracted from the transfer curves reveals that the chemical doping process in disordered DPP-2T-TT copolymer film is more efficient than that of PBTTT film. These results are somewhat contrary to the general observation that neutral molecule doping such as F4-TCNQ was effectively worked in a thiophene-based highly crystalline polymer rather than a D-A type copolymer. However, optical and structural investigations using UV-vis spectroscopy and grazing incident X-ray diffraction (GIXRD) have shown that the structural factors of the polymer semiconductors have a greater influence than the chemical characteristics between the polymer semiconductors and the ionic species in electrolyte. |
Thursday, March 7, 2019 1:27PM - 1:39PM |
S50.00010: High performance organic field-effect transistors with wire bar-coated semiconducting polymer film Do Yeon Kim, Jiyoul Lee We fabricated high performance organic field-effect transistors (OFETs) with wire bar-coated semiconducting polymer film as an active layer. For an active layer of the OFETs, we employed cyclopentadithiophene–benzothiadiazole (CDT–BTZ) donor-acceptor (D-A) type copolymers consisting of CDT as an electron-donating unit and BTZ as an electron-accepting unit. The OFETs with bar-coated CDT-BTZ semiconducting copolymer films shows about five times higher field-effect mobility of 0.51cm2/Vs than 0.11 cm2/Vs of the OFETs with spin-coated CDT-BTZ film, although the charge carrier mobility of the D-A type semiconducting copolymer is less critical to the degree of alignment of the semiconducting polymer. Overall, the results demonstrate that the wire bar-coating process offer opportunities to enhance the performance of the OFETs. |
Thursday, March 7, 2019 1:39PM - 1:51PM |
S50.00011: Polymer light emitting field effect transistors with steadily high efficiency over three orders of magnitude of current BANG-YU HSU To simultaneously achieve efficient and intensified optical output is the most challenging task for polymeric light emitting field effect transistors (PLEFETs). A p-type unipolar PLEFET with high brightness but oversaturated holes will limit recombination efficiency. Instead, an ambipolar PLEFET with high recombination current will decrease on/off ratio. An ideal solution will be the combined advantages of both LEFETs, significant on/off ratio, high current density, and efficient recombination. A bilayer PLEFET can meet the three criteria satisfactorily by applying asymmetric organic/inorganic-hybrid transparent contacts. Hole/electron injections and photon output in a p-type PLEFETs was simultaneously improved. For source-drain current over 3 orders of magnitude from sub-micro ampere to sub-mini ampere, corresponding to 26 to 3747 cd/m2, external quantum efficiency (EQE) steadily sustained 0.5%. EQE of the PLEFETs in this work was enhanced remarkably, 0.5% vs. < 0.08% (conventional ones), and on/off ratio remained high at 104-105. Asymmetric organic/inorganic-hybrid transparent contacts demonstrated a promising strategy for energy-efficient PLEFETs. |
Thursday, March 7, 2019 1:51PM - 2:03PM |
S50.00012: A Molecularly- Imprinted Electrochemical Sensor to Detect VOCs in the Breath Print of Lung Cancer Patients. Shadi Emam, Nian Xiang Sun
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Thursday, March 7, 2019 2:03PM - 2:15PM |
S50.00013: Low-power photonic organic artificial synapse inspired by dopamine-facilitated synaptic activity Seonggil Ham, Sanghyeon Choi, Haein Cho, Gunuk Wang The ability of the synaptic plasticity in an artificial synapse can offer significant improvement in low-power recognition, and learning capability in a neuromorphic system [1]. Inspired by light-assisted dopamine-facilitated, which achieves rapid learning and adaptation by lowering the threshold of the synaptic plasticity, we fabricate a organolead halide perovskite (OHP)-based photonic synapse in which the synaptic plasticity is modified by both electrical pulses and light illumination. Owing to the accelerated migration of the iodine vacancy inherently existing in the OHP film under light illumination, the OHP synaptic device exhibits light-tunable synaptic functionalities with very low programming inputs (~0.1 V). It is also demonstrated that the threshold of the long-term potentiation decreases and synaptic weight further modulates when light illuminates the device. Notably, under light exposure, the OHP synaptic device achieves rapid pattern recognition with ~81.8% accuracy with a low power consumption (4.82 nW/the initial update for potentiation), which is ~2.6×103 times lower than when the synaptic weights are updated by only high electrical pulses. |
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