Huaping Zhao

Electric Current Induced Reduction of Graphene Oxide and Its Application as Gap Electrodes in Organic Photoswitching Devices

This is owing to its exceptional physicochemical, electrical, mechanical, and biocompatible properties, which mean graphene-based materials have great prospects for applications in nanoscience and advanced materials. [ 1–3 ] Since the revival of the investigation of graphene in 2004, [ 4 ] various chemical and physical protocols have been developed to produce graphenebased materials. [ 1–8 ] Among these, chemical exfoliation of bulk graphite by intercalation using strong oxidizing acids has received much attention, since it can produce graphene-based materials on a large scale easily with low cost. [ 7 , 8 ]

High-performance organic single-crystal field-effect transistors of indolo[3,2-b]carbazole and their potential applications in gas controlled organic memory devices.

Organic fi eld-effect transistors (OFETs) have attracted considerable attention because of their potential applications in inverters, display driving circuits, memory cells, sensors, and so on. [ 1 ] High charge-carrier mobility, good environmental stability, and low fabrication cost are the three key factors to realize the goals. Many series of organic semiconductors with rational design have been synthesized to meet these demands. [ 2 ] Linearacene-based OFETs show high mobilities because of the strong extended π – π interaction and enhanced intermolecular overlapping of acene molecules. [ 3–9 ] For instance, pentacene, a representative with fi ve linear acene rings, shows high charge carrier mobilities of above 1 cm 2 V − 1 s − 1 in the form of a single crystal [ 3 ]

High‐Performance Organic Nanoscale Photoswitches Based on Nanogap Electrodes Coated with a Blend of Poly(3‐hexylthiophene) and [6,6]‐Phenyl‐C61‐butyric Acid Methyl Ester (P3HT:PCBM)

[*] Prof. W. P. Hu, Dr. H. L. Dong, H. F. Zhu, T. Li, Y. J. Zhang, Dr. H. P. Zhao, Z. M. Wei, Dr. W. Xu Key Laboratory of Organic Solids Beijing National Laboratory for Molecular Sciences Institute of Chemistry Chinese Academy of Sciences Beijing 100190 (P. R. China) E-mail: huwp@iccas.ac.cn; dhl522@iccas.ac.cn Prof. Z. S. Bo, J. S. Song Key Laboratory of Polymer Physics and Chemistry Beijing National Laboratory for Molecular Sciences Institute of Chemistry Chinese Academy of Sciences Beijing 100190 (P. R. China) E-mail: zsbo@iccas.ac.cn

GaAs-based room-temperature continuous-wave 1.59 {mu}m GaInNAsSb single-quantum-well laser diode grown by molecular-beam epitaxy

Starting from the growth of high-quality 1.3μmGaInNAs∕GaAs quantum well (QW), the QW emission wavelength has been extended up to 1.55μm by a combination of lowering growth rate, using GaNAs barriers and incorporating some amount of Sb. The photoluminescence properties of 1.5μm range GaInNAsSb∕GaNAs QWs are quite comparable to the 1.3μm QWs, revealing positive effect of Sb on improving the optical quality of the QWs. A 1.59μm lasing of a GaInNAsSb∕GaNAs single-QW laser diode is obtained under continuous current injection at room temperature. The threshold current density is 2.6kA∕cm2 with as-cleaved facet mirrors.

New type of organic semiconductors for field-effect transistors with carbon-carbon triple bonds

A series of thiophene-phenylene semiconductors containing –CC– bonds were designed and synthesized. Their thermal, optical, electrochemical and FET properties were fully characterized. The crystal structure of 5,5′-bis(phenylethynyl)-2,2′-bithiophene (1c) revealed that the introduction of carbon-carbon triple bonds efficiently eliminated the steric repulsions between adjacent aromatic rings. TGA, UV-vis spectra and electrochemical measurements showed that all compounds had good thermal and environmental stability. FET devices based on these materials exhibited high performance and stability. All the results suggested the introduction of carbon-carbon triple bonds provided an efficient route to high performance organic semiconductors.

Substitution effect on molecular packing and transistor performance of indolo[3,2-b]carbazole derivatives

In this manuscript, two chloro-substituted derivatives of indolo[3,2-b]carbazole (ICZ), 2,8-dichloro-indolo[3,2-b]carbazole (CICZ) and 2,8-dichloro-5,11-dihexyl-indolo[3,2-b]carbazole (CHICZ) were designed and synthesized. The only difference between CICZ and CHICZ is at the N-5 and N-11 positions with or without long alkyl side chains. Interestingly, CICZ and CHICZ exhibited similar thermal, optical, and electrochemical properties, while their molecular packing motifs in solid state and corresponding charge transport properties were significantly different. The alkyl chains at N-5 and N-11 positions were proved not only enhancing the solubility and self-organization of the compounds but also shifting the molecular packing from herringbone (CICZ) to one-dimensional π–π stacking (CHICZ). Moreover, nearly no field-effect performance was observed for CICZ, while the mobility of CHICZ was as high as 0.14 cm2 V−1 s−1 for its thin films and 0.5 cm2 V−1 s−1 for its single crystals. These results confirmed that the chemical substitutions are a powerful molecular design tool to tune the molecular packing motifs of organic semiconductors and their corresponding electronic properties.

Towards high quality triangular silver nanoprisms: improved synthesis, six-tip based hot spots and ultra-high local surface plasmon resonance sensitivity

The great application potential of triangular silver nanoprisms (TSNPRs, also referred to as triangular silver nanoplates) is hampered by the lack of methods to produce well-defined tips with high monodispersity, with easily removable ligands. In this work, a simple one-step plasmon-mediated method was developed to prepare monodisperse high-quality TSNPRs. In this approach, the sole surface capping agent was the easily removable trisodium citrate. Differing from common strategies using complex polymers, OH(-) ions were used to improve the monodispersity of silver seeds, as well as to control the growth process through inhibiting the oxidation of silver nanoparticles. Using these monodisperse high-quality TSNPRs as building blocks, self-assembled TSNPRs consisting of six-tip based hot spots were realized for the first time as demonstrated in a high enhancement (∼10(7)) of surface-enhanced Raman scattering (SERS). From the plasmon band shift versus the refractive index, ultra-high local surface plasmon resonance sensitivity (413 nm RIU(-1) or 1.24 eV RIU(-1), figure of merit (FOM) = 4.59) was reached at ∼630 nm, making these materials promising for chemical/biological sensing applications.

Development of organic field-effect properties by introducing aryl-acetylene into benzodithiophene

Ethynylene-containing benzo[1,2-b:4,5-b′]dithiophene derivatives 1a–c (BPEBDT, BTEBDT and BHPEBDT) were designed and synthesized. Their physicochemical properties were studied by absorption spectra and electrochemistry. 1a–c displayed high field-effect transistors performance, a mobility up to 1.17 cm2 V−1 s−1 with on/off current ratio of 107 was achieved.

Influence of Intermolecular NH⋅⋅⋅π Interactions on Molecular Packing and Field‐Effect Performance of Organic Semiconductors

Charge transport in organic semiconductors is strongly dependent on their molecular packing modes in the solid state. Therefore, understanding the relationship between molecular packing and charge transport is imperative, both experimentally and theoretically. However, so far, the fundamental effects of solid-state packing and molecular interactions (e.g. N-H...pi) on charge transport need further elucidation. Herein, indolo[3,2-b]carbazole (ICZ) and a derivative thereof are used as examples to approach this scientific target. An interesting insight obtained thereby is that N-H...pi interactions among ICZ molecules facilitate charge transport for higher mobility. Subtle changes in the of N-H...pi interactions can significantly influence both the molecular packing and the charge-transport properties. Therefore, a method for exploiting intermolecular N-H...pi interactions would yield novel molecular systems with designable characteristics.

1.55 {mu}m GaInNAs resonant-cavity-enhanced photodetector grown on GaAs

We report the design, growth, fabrication, and characterization of a GaAs-based resonant-cavity-enhanced (RCE) GaInNAs photodetector operating at 1.55μm. The structure of the device was designed using a transfer-matrix method (TMM). By optimizing the molecular-beam epitaxy growth conditions, six GaInNAs quantum wells were used as the absorption layers. Twenty-five (25)- and 9-pair GaAs∕AlAs-distributed Bragg reflectors were grown as the bottom and top mirrors. At 1.55μm, a quantum efficiency of 33% with a full width at half maximum of 10nm was obtained. The dark current density was 3×10−7A∕cm2 at a bias of 0V and 4.3×10−5A∕cm2 at a reverse bias of 5V. The primary time response measurement shows that the device has a rise time of less than 800ps.