A study of effects of electrode contacts on performance of organic-based light-emitting field-effect transistors

Kim, Dae-Kyu,Choi, Jong-Ho Elsevier 2018 Optical Materials Vol.76 No.-

<P><B>Abstract</B></P> <P>Herein is presented a comparative performance analysis of heterojunction organic-based light-emitting field-effect transistors (OLEFETs) with symmetric (Au only) and asymmetric (Au and LiF/Al) electrode contacts. The devices had a top source–drain contact with long-channel geometry and were produced by sequentially depositing <I>p</I>-type pentacene and <I>n</I>-type <I>N,N</I>′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13) using a neutral cluster beam deposition apparatus. The spectroscopic, structural and morphological properties of the organic thin films were examined using photoluminescence (PL) spectroscopy, X-ray diffraction (XRD) method, laser scanning confocal and atomic force microscopy (LSCM, AFM). Based upon the growth of high-quality, well-packed crystalline thin films, the devices demonstrated ambipolar field-effect characteristics, stress-free operational stability, and light emission under ambient conditions. Various device parameters were derived from the fits of the observed characteristics. The hole mobilities were nearly equal irrespective of the electrode contacts, whereas the electron mobilities of the transistors with LiF/Al drain electrodes were higher due to the low injection barrier. For the OLEFETs with symmetric electrodes, electroluminescence (EL) occurred only in the vicinity of the hole-injecting electrode, whereas for the OLEFETs with asymmetric electrodes, the emission occurred in the vicinity of both hole- and electron-injecting electrodes. By tuning the carrier injection and transport through high- and low-work function metals, the hole-electron recombination sites could be controlled. The operating conduction and light emission mechanism are discussed with the aid of EL images obtained using a charge-coupled device (CCD) camera.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The OLEFETs demonstrated ambipolar characteristics and light emission in air. </LI> <LI> The operating light emission mechanisms are discussed with the aid of EL images. </LI> <LI> The electron mobilities of the OFETs with LiF/Al drain electrodes were improved. </LI> </UL> </P>

Electrical Properties of CuPc FET with Different Substrate Temperature

Ho Shik Lee,Yong Pil Park,Min Woo Cheon 한국전기전자재료학회 2007 Transactions on Electrical and Electronic Material Vol.8 No.4

Organic field-effect transistors (OFETs) are of interest for use in widely area electronic applications. We fabricated the organic field-effect transistor based a copper phthalocyanine (CuPc) as an active layer on the silicon substrate. The CuPc FET device was made a top-contact type and the substrate temperature was room temperature and 150 ℃. The CuPc thickness was 40 nm, and the channel length was 50 m, channel width was 3 mm. We observed the typical current-voltage (I-V) characteristics and capacitance-voltage (C-V) in CuPc FET and we calculated the effective mobility with each device. Also, we observed the AFM images with different substrate temperature.

Overcoating BaTiO₃ dielectrics with a fluorinated polymer to produce highly reliable organic field-effect transistors

Jeong, Yong Jin,Kim, Dong Hun,Kang, Young-Min,An, Tae Kyu Elsevier S.A. 2019 Thin Solid Films Vol.685 No.-

<P><B>Abstract</B></P> <P>High-dielectric constant (<I>κ</I>) materials have been extensively investigated for several potential applications, particularly in low-voltage-operating organic field-effect transistors (OFETs). To ensure the operational stability of the OFET, the interface between the organic semiconductor and the high-<I>κ</I> dielectric should be fully controlled. In the current work, we overcoated a fluorinated polymer, namely poly(pentafluorostyrene) (PFS), onto one of the high-<I>κ</I> materials, namely barium titanate (BaTiO<SUB>3</SUB>), and used this bilayer to fabricate highly stable OFETs. The surfaces of the BaTiO<SUB>3</SUB> dielectric layers were effectively modified with the PFS overcoating. Compared to the uncoated BaTiO<SUB>3</SUB>, the PFS/BaTiO<SUB>3</SUB> bilayer dielectric showed significantly reduced leakage current and altered surface properties. The smoothness of the surfaces of the PFS/BaTiO<SUB>3</SUB> films appeared to have been responsible for the observed improved crystal structures of the overlying pentacene molecules. In addition, the surface dipoles and electron-withdrawing character of the PFS/BaTiO<SUB>3</SUB> films built a high hole injection barrier between the semiconductor and dielectric layers, with this barrier blocking hole trapping. Finally, overcoating BaTiO<SUB>3</SUB> with PFS allowed the resulting PFS/BaTiO<SUB>3</SUB> to be utilized as a gate dielectric layer for highly stable OFETs during low-voltage operation. These OFETs exhibited hysteresis-free transistor performances and reliable operation under a sustained gate-bias stress in air.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fluorinated polymer was overcoated on high-<I>κ</I> BaTiO<SUB>3</SUB> dielectric film. </LI> <LI> Overcoating of the fluorinated polymer allowed BaTiO<SUB>3</SUB> film to exhibit good surface morphologies, insulating properties. </LI> <LI> The OFETs prepared with fluorinated polymer/BaTiO<SUB>3</SUB> dielectric film improved reliable performances under gate-bias stress. </LI> </UL> </P>

Novel naphthalene-diimide-based small molecule with a bithiophene linker for use in organic field-effect transistors

Ha, Yeon Hee,Oh, Jong Gyu,Park, Sejin,Kwon, Soon-Ki,An, Tae Kyu,Jang, Jaeyoung,Kim, Yun-Hi Elsevier 2018 ORGANIC ELECTRONICS Vol.63 No.-

<P><B>Abstract</B></P> <P>We report on the synthesis and characterization of a novel naphthalene diimide (NDI)-based small molecule with a bithiophene linker unit, NDI-BT-NDI-EH, for application as a solution-processable <I>n</I>-channel active material in organic field-effect transistors (OFETs). NDI-BT-NDI-EH was synthesized <I>via</I> the Stille coupling reaction and the bithiophene linker unit was introduced as a rotatable linker between two NDI cores to improve the solubility of NDI-BT-NDI-EH while maintaining its high field-effect mobility. We found that the crystallinity and molecular ordering of NDI-BT-NDI-EH thin films could be improved by thermal annealing; a moderate annealing temperature of 120 °C appeared to be optimal for promoting self-organization among the NDI-BT-NDI-EH molecules. The NDI-BT-NDI-EH molecules in thermally annealed thin films mainly adopted an edge-on orientation with improved <I>π</I>-<I>π</I> stacking on the surface of octyltrichlorosilane-treated SiO<SUB>2</SUB> substrates, which is favorable for lateral charge transport. As a result, the optimally annealed NDI-BT-NDI-EH OFET exhibited evident <I>n</I>-type OFET characteristics with high field-effect mobilities of up to 0.016 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP> and an on/off ratio of 1.4 × 10<SUP>5</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel NDI-based organic small molecular semiconductor is synthesized <I>via</I> the Stille coupling reaction. </LI> <LI> A rotatable bithiophene linker unit in NDI-BT-NDI-EH improves solubility while maintaining high carrier mobility. </LI> <LI> Thermally annealed NDI-BT-NDI-EH molecules show an edge-on orientation with increased crystallinity. </LI> <LI> NDI-BT-NDI-EH-based <I>n</I>-type OFETs exhibit high performance with <I>μ</I> <SUB> <I>e</I> </SUB> of up to 0.016 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

N형 고분자 반도체의 전하주입 특성 향상을 통한 저전압 유기전계효과트랜지스터 특성 연구

문지훈,백강준,Moon, Ji-Hoon,Baeg, Kang-Jun 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.10

Herein, we report the fabrication of low-voltage N-type organic field-effect transistors by using high capacitance fluorinated polymer gate dielectrics such as P(VDF-TrFE), P(VDF-TrFE-CTFE), and P(VDF-TrFE-CFE). Electron-withdrawing functional groups in PVDF-based polymers typically cause the depletion of negative charge carriers and a high contact resistance in N-channel organic semiconductors. Therefore, we incorporated intermediate layers of a low-k polymerto prevent the formation of a direct interface between PVDF-based gate insulators and the semiconducting active layer. Consequently, electron depletion is inhibited, and the high charge resistance between the semiconductor and source/drain electrodes is remarkably improved by the in corporation of solution-processed charge injection layers.

Synthesis and characterization of an ester-terminated organic semiconductor for ethanol vapor detection

An, T.K.,Yun, H.J.,Narote, R.,Kim, R.,Lee, S.U.,Kim, Y.,Nam, S.,Cha, H.,Jeong, Y.J.,Kim, K.,Cho, S.,Kwon, S.K.,Kim, Y.H.,Park, C.E. Elsevier Science 2014 ORGANIC ELECTRONICS Vol.15 No.10

An organic-field effect transistor (OFET) based on a newly synthesized organic molecule with an ester end group (ANOAT) was tested in a sensor for the detection of ethanol vapor. The linearly fused acene in ANOAT forms channel layers in the OFET and the ester end group of ANOAT interacts with ethanol vapor. The ethanol sensing ability of the ANOAT-based OFET derives not from changes in the crystalline structure of the organic semiconductor but from the interaction between ethanol vapor and the ester end group, which we demonstrated by using FT-IR analysis, computational modeling, X-ray scattering, and AFM analysis.

Identification of Bias-Stress Effect and Charge Trap Mechanism in Organic Field-Effect Transistors Depending on Molecular Weights of Polymethyl methacrylate (PMMA) Insulator

정유정,임재민,한송연,김수진,송원성,최현호 한국공업화학회 2022 한국공업화학회 연구논문 초록집 Vol.2022 No.-

Low-voltage organic transistors and inverters using HfO_x dielectrics

Oh, J.D.,Kim, J.W.,Kim, D.K.,Choi, J.H. Elsevier Science 2016 ORGANIC ELECTRONICS Vol.30 No.-

Based on the p-type pentacene and n-type N,N'-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13), low-voltage organic field-effect transistors (OFETs) and inverters using hafnium (Hf)-based dielectrics were produced and characterized. All the pristine and cyclic olefin copolymer (COC)-passivated HfO<SUB>x</SUB> gate dielectrics were deposited by the solution-processed sol-gel chemistry, and organic thin films were deposited on the dielectrics by the neutral cluster beam deposition method. In comparison to the pristine HfO<SUB>x</SUB>-based OFETs, the COC-passivated transistors showed better device performance: higher hole and electron mobilities, reduced hysteresis, decreased trap densities, and particularly improved operational stability of n-type transistors. The inverters composed of the optimized p- and n-type OFETs with the asymmetric Au and LiF/Al electrodes using COC-passivated HfO<SUB>x</SUB> dielectrics exhibited high gains and good noise margins under ambient conditions.

Fluorinated Polyimide Gate Dielectrics for Transparent Organic Field-Effect Transistor and Logic Gate Circuit with Electrical Stability

민홍기,강보석,조정호 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

Fluorinated polyimides gate dielectric based on 6FDA-TFDB-PI and 6FDA-BisAAF-PI were synthesized to use as a gate dielectric to fabricate high performance organic field-effect transistors. The fluorine substituted into polyimide chain was improved the efficiency of solutionprocess to make uniform films. These fluorinated polyimide make it possible to fabricate transparent devices. Especially, OFETs based on 6FDA-TFDB-PI which has low surface energy have high-performance because defect density formed by grain boundary is lowest. The OFETs based on 6FDA-TFDB-PI gate dielectric have high carrier mobility and a high on/off ratio exceeding 106. And, we show that the devices have excellent electrical stability from measured bias stress test.

Photopatternable Conducting Polymer Nanocomposite with Incorporated Gold Nanoparticles for Use in Organic Field Effect Transistors

허성,최현호,조길원,김승빈 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.4

We investigated a new method for patterning organic field-effect transistors (OFETs) using a photopatternable conducting polymer nanocomposite, consisting of poly(3-hexylthiophene) (P3HT)-coated gold nanoparticles (AuNPs) that had been modified with a photoreactive cinnamate group, to form P3HT-AuNP-CI. We found that the addition of the cinnamate group to the nanoparticle surface assisted the preparation of a solventresistive semiconducting film and preserved the P3HT ordering, which was interrupted by Au-P3HT interactions, as well as provided UV-controllable electrical properties. The P3HT-AuNPs-CI films could be microscale-patterned via a UV crosslinking photoreaction, represented as a promising photopatternable semiconductor material for use in advanced applications, with tunable electrical properties for fabrication of sub-micron and microscale electronic devices.