Gang Yu

NiCo2O4 nanowire arrays supported on Ni foam for high-performance flexible all-solid-state supercapacitors

Portable electronic devices which are ultrathin, lightweight and even able to roll-up have attracted much attention. Herein, we report the design of flexible all-solid-state symmetric supercapacitors by using two NiCo2O4 nanowire arrays supported on Ni foams as the electrodes. The as-fabricated symmetric supercapacitors have excellent electrochemical performance with a high cell areal capacitance of 161 mF cm−2 at 1 mA cm−2. Good electrochemical performance stability over 3000 cycles was obtained even when the device was under harsh mechanical conditions including both twisted and bent states. As-fabricated all-solid-state supercapacitors could be charged and power a commercial light-emitting-diode, demonstrating their feasibility as an efficient energy storage component and self-powered micro/nano-system. In addition, we were able to grow NiCo2O4 nanowire arrays on many kinds of flexible substrates, including nickel foam, carbon cloth, Ti foil and polytetrafluoroethylene tape. Our work here opens up opportunities for the device configuration for energy-storage devices in the future wearable electronic area and many other flexible, lightweight and high performance functional nanoscale devices.

High-detectivity InAs nanowire photodetectors with spectral response from ultraviolet to near-infrared

AbstractInAs is a direct, narrow band gap (0.354 eV) material with ultrahigh electron mobility, and is potentially a good optoelectronic device candidate in the wide UV-visible-near-infrared region. In this work we report the fabrication of InAs nanowire-based photodetectors, which showed a very high photoresponse over a broad spectral range from 300 to 1,100 nm. The responsivity, external quantum efficiency and detectivity of the device were respectively measured to be 4.4 × 103 AW−1, 1.03 × 106%, and 2.6 × 1011 Jones to visible incident light. Time dependent measurements at different wavelengths and under different light intensities also demonstrated the fast, reversible, and stable photoresponse of our device. Theoretical calculations of the optical absorption and the electric field component distribution were also performed to elucidate the mechanism of the enhanced photoresponse. Our results demonstrate that the single-crystalline InAs NWs are very promising candidates for the design of high sensitivity and high stability nanoscale photodetectors with a broad band photoresponse.

High-Performance Hybrid Phenyl-C61-Butyric Acid Methyl Ester/Cd3P2 Nanowire Ultraviolet-Visible-Near Infrared Photodetectors

In this work, single-crystalline p-type Cd3P2 nanowires (NWs) were synthesized on a Cd sheet via a facile chemical vapor deposition method. Then field-effect transistors and high-performance photodetectors were fabricated based on these NWs. It was found that hole mobility of a pristine Cd3P2 NW is around 2.94 cm(2) V(-1) s(-1). Meanwhile, high responsivity and photoconductive gain were observed on these devices across a broad spectral range covering UV-visible to NIR with high stability and reproducibility. Furthermore, hybrid organic-inorganic n-type phenyl-C61-butyric acid methyl ester (PCBM) and p-type Cd3P2 NW heterojunction photodetectors were also fabricated, exhibiting much improved photocurrent and photoconductive gain, as compared to the device made of pristine Cd3P2 NWs. Intriguingly, the flexible hybrid photodetectors have been fabricated on plastic substrates and characterized under various bending conditions, demonstrating their excellent flexibility and robustness. The high performance and flexibility of the hybrid photodetectors are promising for further applications requiring large-area, high-sensitivity, and high-speed photodetectors with broad-spectrum photoresponse.

Fabrication of high-quality ZnTe nanowires toward high-performance rigid/flexible visible-light photodetectors

ZnTe is an important p-type semiconductor with great applications as field-effect transistors and photodetectors. In this paper, individual ZnTe nanowires based field-effect transistors was fabricated, showing evident p-type conductivity with an effect mobility of 11.3 cm(2)/Vs. Single ZnTe nanowire based photodetectors on rigid silicon substrate exhibited high sensitivity and excellent stability to visible incident light with responstivity and quantum efficiency as high as 1.87 × 10(5) A/W and 4.36 × 10(7)% respectively and are stable in a wide temperature range (25-250 °C). The polarization-sensitivity of the ZnTe nanowires was studied for the first time. The results revealed a periodic oscillation with the continuous variation of polarization angles. Besides, flexible photodetectors were also fabricated with the features of excellent flexibility, stability and sensitivity to visible incident light. Our work would enable application opportunities in using ZnTe nanowires for ultrahigh-performance photodetectors in scientific, commercial and industrial applications.

High performance rigid and flexible visible-light photodetectors based on aligned X(In, Ga)P nanowire arrays

InP and GaP nanowires (NWs) were synthesized via a simple thermal evaporation method for applications as high performance visible-light photodetectors. Individual InP NW field-effect transistors (FETs) were fabricated to study their electronic transport and photoresponse characteristics, which exhibited typical n-type transistor characteristics with an efficient electron mobility of 1.21 cm2 V−1 s−1, a fast response time (∼0.1 s) and good sensitivity with a spectral responsivity of 779.14 A W−1 and a high quantum efficiency of 1.53 × 105% to visible light irradiation. Using the contact printing process, large scale aligned InP NW arrays were assembled on both rigid SiO2/Si and flexible PET substrates. Both rigid and flexible InP NW array based photodetectors demonstrated excellent photoresponse performance, especially a faster response, for example, from 0.1 s to 80 ms. In addition, the flexible InP NW array based photodetectors exhibited good flexibility, good folding endurance and electrical stability. Using similar processes, aligned GaP NW array based photodetectors were also fabricated on SiO2/Si and PET substrates, which also exhibited fast, reversible, and stable photoresponse properties. These merits demonstrate that the as-prepared InP and GaP NWs are good candidates with substantial potential for future electronic and optoelectronic nanodevice applications.

Contact printing of horizontally aligned Zn2GeO4 and In2Ge2O7 nanowire arrays for multi-channel field-effect transistors and their photoresponse performances

The ternary oxides, Zn2GeO4 and In2Ge2O7 nanowires, are promising n-type semiconductors with outstanding transport properties for high performance electronic devices. By using the direct contact printing process, we reported the assembly of horizontally aligned Zn2GeO4 and In2Ge2O7 nanowire arrays to be used as building blocks for high performance multi-channel field-effect transistors. The as-fabricated multi-channel transistors exhibited higher voltage stability and repeatability than their single nanowire based counterparts. The effective mobilities of the multi-channel field-effect transistors were calculated to be 25.44 cm2 V−1 s−1 and 11.9 cm2 V−1 s−1, comparable to the single-channel FETs. The as-fabricated multi-channel transistors were also used as high performance photodetectors, exhibited a high sensitivity to ultraviolet light illumination with a photoconductive gain and quantum efficiency as high as 1.034 × 105 and 1.032 × 107% for Zn2GeO4 nanowires and 2.58 × 105 and 2.617 × 107% for In2Ge2O7 nanowires.

Flexible photodetectors with single-crystalline GaTe nanowires

GaTe is an important layer-structured III–VI compound semiconductor with superior optical and electrical properties. In this paper, single-crystalline gallium telluride nanowires were successfully synthesized via a conventional chemical vapor deposition method. Single nanowire field-effect transistors revealed typical p-type semiconductor behavior of the GaTe nanowires, which showed substantial response to light irradiation with broad wavelengths ranging from 350 to 800 nm. Flexible photodetectors on a PET substrate were also fabricated with a high responsivity and an external quantum efficiency of 20.75 A W−1 and 3.96 × 103%, respectively. Besides, the flexible photodetectors showed excellent mechanical flexibility and stable electrical properties under different bending states, revealing promising applications in future flexible optoelectronic devices.

Contact printing of horizontally-aligned p-type Zn3P2 nanowire arrays for rigid and flexible photodetectors

Zn(3)P(2) is an important p-type semiconductor with the ability to detect almost all visible and ultraviolet light. By using the simple and efficient contact printing process, we reported the assembly of horizontally-aligned p-type Zn(3)P(2) nanowire arrays to be used as building blocks for high performance photodetectors. Horizontally-aligned Zn(3)P(2) nanowire arrays were first printed on silicon substrate to make thin-film transistors, exhibiting typical p-type transistor behavior with a high on/off ratio of 10(3). Besides, the Zn(3)P(2) nanowire array based devices showed a substantial response to illuminated lights with a wide range of wavelengths and densities. Flexible photodetectors were also fabricated by contact printing of horizontally-aligned Zn(3)P(2) nanowire arrays on flexible PET substrate, showing a comparable performance to the device on rigid silicon substrate.

Ladder-like metal oxide nanowires: Synthesis, electrical transport, and enhanced light absorption properties

Transparent metal oxide nanowires (NWs) have attracted intense research interest in recent years. We report here the synthesis of interesting ladder-like metal oxide NWs, including In2O3, SnO2, ZnO, and Ga2O3, via a facile chemical vapor deposition (CVD) method. Their structural features and growth mechanism are demonstrated in detail by using the ladder-like In2O3 NWs as an example. Single ladder-like NW-based field-effect transistors (FETs) and photodetectors (PDs) of SnO2 were fabricated in order to investigate their electrical transport and light absorption properties. Compared with straight NW-based FETs which operate in an enhancement mode (E-mode), FETs build on ladder-like NWs operate in a depletion mode (D-mode). The ladder-like NWs also give higher carrier concentrations than conventional single nanowires. Finite-difference time-domain (FDTD) simulations have been performed on the ladder-like NWs and the results reveal a great enhancement of light absorption with both transverse-electric (TE) and transverse-magnetic (TM) polarization modes, which is in good agreement with the experimental results.