用于光电集成的InP基HBT新结构

对用于光电集成(OEIC)的InP基异质结双极性晶体管(HBT)进行了分析,提出了一种新的集电区外延结构,该结构是在单HBT(SHBT)的集电区与次集电区间加入特定厚度与掺杂浓度的p-InGaAs层和n-InP层,既适用于集成光探测器,又较好地解决了SHBT反向击穿电压低、传统双HBT(DHBT)电子堆积效应等问题,并具有外延层生长简单、集电区电子漂移速率高等优点.     

End-capped Thiophene Modulated Molecular Packing in 2,8-Dibenzothiophene-based Materials：from Face-to-face to Edge-to-face Stacking

Two new organic crystals of 2,8-bisthienyldibenzothiophene(BTDT) and 2,8-bis-dithienyldibenzothiophene(BDTDT) compounds were successfully obtained.The change of end-capped group from thiophene to dithiophene causes big differences in molecular packing and carrier-transport property.The adjacent molecules of compound BTDT adopt face-to-face π stacking and exhibit two-dimensional interchain interactions.On the contrary,BDTDT molecules are arranged in an edge-to-face motif and show mainly one-dimensional interacting character.The packing mode exerts dramatic effect on the carrier-transport property.The crystal of BTDT belongs to the orthorhombic system,space group P21212 with a = 20.1427(11),b = 4.6016(3),c = 8.6340(5) ,V = 800.27(8) 3,Z = 2,Dc = 1.446 g/cm3,F(000) = 360,S = 1.019,the final R = 0.0491 and wR = 0.0960 for 1605 reflections with I > 2σ(I).The crystal of BDTDT belongs to the orthorhombic system,space group P212121 with a = 7.2636(15),b = 25.359(5),c = 25.359 ?,V = 4670.9(14) ?3,Z = 8,Dc = 1.458 g/cm3,F(000) = 2112,S = 0.880,the final R = 0.0597 and wR = 0.1318 for 8047 reflections with I > 2σ(I).     

Molecular organization in MAPLE‐deposited conjugated polymer thin films and the implications for carrier transport characteristics

The morphological structure of poly(3‐hexylthiophene) (P3HT) thin films deposited by both Matrix Assisted Pulsed Laser Evaporation (MAPLE) and solution spin‐casting methods are investigated. The MAPLE samples possessed a higher degree of disorder, with random orientations of polymer crystallites along the side‐chain stacking, π–π stacking, and conjugated backbone directions. Moreover, the average molecular orientations and relative degrees of crystallinity of MAPLE‐deposited polymer films are insensitive to the chemistries of the substrates onto which they were deposited; this is in stark contrast to the films prepared by the conventional spin‐casting technique. Despite the seemingly unfavorable molecular orientations and the highly disordered morphologies, the in‐plane charge carrier transport characteristics of the MAPLE samples are comparable to those of spin‐cast samples, exhibiting similar transport activation energies (56 vs. 54 meV) to those reported in the literature for high mobility polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 39–48     

Direct investigations of the interface impedance of organic field-effect transistors with self-assembled-monolayer-modified electrodes

It has been demonstrated that the modification of electrodes with self-assembled monolayers (SAMs) reduces the contact resistance and improves the device performances of organic field-effect transistors (OFETs). However, it has been difficult to judge if the contact resistance was reduced by the change in the electronic properties or by the change in the morphology of the metal–organic interface caused by the SAM modification because they have been difficult to be separately assessed. We have directly investigated the local impedance and the potential difference at the electrode–channel interfaces of the OFETs with and without modification of the electrodes by a pentafluorobenzenethiol SAM using frequency-modulation scanning impedance microscopy (FM-SIM). The potential profile measurement and the FM-SIM measurement at the interface showed that the improvement of the field-effect mobility in the SAM-modified OFET was caused by the reduction of the energy level mismatch, namely, the hole injection barrier at the source–channel interface, presumably with the reduction of the hole trap sites at the source–channel interface.     

Fast detection of blood gases by solution gated organic field effect transistors

We characterize the electrochemical stability of the organic semiconductor Dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) in aqueous solutions. Electrochemical stability of DNTT in solution is validated by cyclic voltammetry and demonstrated by solution gating of DNTT organic field effect transistors (OFETs). Then, we investigate the response time of DNTT OFETs to ammonia, a common blood gas. For bare OFETs, the response time to ammonia is 1–2s only. The exact response time depends on the DNTT film morphology; the fastest response is obtained for pronounced 3D (Volmer-Weber) growth. By comparing OFETs with and without a semipermeable parylene-C encapsulation layer, the influence of the capping on the response time is investigated. An encapsulation layer of 86 nm prolongs the response time to 100s, indicating that parylene-C acts as an efficient diffusion barrier for ammonia.     

EDOT‐diketopyrrolopyrrole copolymers for high bulk hole mobility and near infrared absorption

To obtain novel low‐bandgap materials with tailored hole‐transport properties and extended absorption, electron rich 3,4‐ethylenedioxythiophene is introduced as a comonomer in diketopyrrolo[3,4‐c]pyrrole copolymers with different aryl flanking units. The polymers are characterized by absorption and photoluminescence spectroscopy, dynamic scanning calorimetry, cyclic voltammetry, and X‐ray diffraction. The charge transport properties of these new materials are studied carefully using an organic field effect transistor geometry where the charge carriers are transported over a narrow channel at the semiconductor/dielectric interface. These results are compared to bulk charge carrier mobilities using space‐charge limited current (SCLC) measurements, in which the charge carrier is transported through the complete film thickness of several hundred nanometers. Finally, charge carrier mobilities are correlated with the electronic structure of the compounds. We find that in particular the thiophene‐flanked copolymer PDPP[T]₂‐EDOT is a very promising candidate for organic photovoltaics, showing an absorption response in the near infrared region with an optical bandgap of 1.15 eV and a very high bulk hole mobility of 2.9 × 10^?4 cm² V^?1 s^?1 as measured by SCLC. This value is two orders of magnitudes higher than SCLC mobilities reported for other polydiketopyrrolopyrroles and is in the range of the well‐known hole transporting polymer poly(3‐hexylthiophene). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 639–648     

Off-resonant activation of optical emission

Recent reports have identified a three-wave optically parametric mechanism for the active enhancement of fluorescence using off-resonant radiation. In this Letter it is shown by numerical simulation that the output of a laser system optically pumped just below threshold, can be strongly enhanced by this mechanism, using an ancillary beam of moderate intensity. The electrodynamics and kinetics of the nonlinear optical mechanism are analyzed, model calculations performed, and the output is illustrated graphically. The response demonstrates a novel method for achieving all-optical transistor action.     

Enzymatic sensing with laccase-functionalized textile organic biosensors

Herein we present a textile wearable electrochemical transistor by functionalizing a single cotton yarn with semiconducting polymer. The organic electrochemical transistor (OECT), which is low cost and completely integrated e-textile, is decorated by adsorption of the fungal laccase POXA1b, and is used as biosensor for the direct detection of Tyrosine (L-Tyr) without the use of electron mediators. The detection of Tyr in real-case scenario such as human physiological fluids would own a paramount importance in noninvasive analysis of the patient's condition, monitoring and preventing several pathologies. To assess the reaction progression, the redox process is studied by UV–visible absorption with test reference molecule of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS): the results confirmed that the oxidation reaction is driven by the presence of laccase enzyme and direct electron transfer occurred. The modulation of the signal response and the kinetic of the signal is used to detect Tyr molecule in aqueous solution and the role of the enzyme adsorption on the textile is analyzed. A kinetic analysis of the characteristic modulation times of the sensing curves, confirm the sensing properties of the textile device. The textile-based biosensor is demonstrated to monitor human health biomarkers through wearable applications in a non-invasive way, finding potential application in sport, healthcare and working safety.     

Synthesis and Characterization of Naphthalene End-Capped Divinylbenzene for OTFT

An organic field-effect transistor was fabricated based on a thin film of 1,4-bis-(2-naphthalen-2-ylvinyl)benzene (BNDV). The organic semiconductor was deposited via thermal evaporation on a chemically modified silicon dioxide surface. The thermal, optical, electronic, and surface properties of the BNDV compound were investigated by thermogravimetric analysis, differential scanning calorimetry, ultraviolet–visible (UV–vis) absorption, photoluminescence spectroscopies, cyclic voltammetry, x-ray diffraction, and atomic force microscopy. The BNDV had good oxidation stability and exhibited a field-effect performance with a mobility of 0.062 cm²/V s, a subthreshold slope of 0.4 V, and an on/off ratio of 2.45 × 10⁵.     

Regular conjugated terpolymers comprising two different acceptors and bithiophene donor in repeating group: Effect of strong and weak acceptors on semiconducting properties

Diketopyrrolopyrrole (DPP)‐based terpolymers—P(DPP‐TPyT) and P(DPP‐T3MTT)—bearing bithiophene donating groups and weak accepting units such as pyridine (Py) or methyl thiophene‐3‐carboxylate (3MT), in the polymer backbone, were successfully synthesized. Although the two polymers had similar physical and electrochemical properties, grazing incidence X‐ray diffraction patterns of P(DPP‐TPyT) and P(DPP‐T3MTT) showed mixed and edge‐on orientations, respectively, in thermally annealed films. Accordingly, the P(DPP‐T3MTT) showed twice the hole mobility of P(DPP‐TPyT) in a thin‐film transistor, and a blended film of P(DPP‐T3MTT) and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC₇₁BM) showed better power conversion efficiency in a polymer solar cell. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1339‐1347