InAs nanowire is an important III-V group semiconducting nanomaterial with direct and narrow bandgap and small effective electron mass. It has great potential in high-performance electronic nanodevices and infrared detectors. In this talk, I will introduce our recent progresses on the structure-dependent properties of InAs nanowires and their devices. Various properties of individual InAs nanowires are studied and correlated with their structures through a comprehensive in situ platform we have developed in a scanning electron microscope. Remarkable piezoelectric and piezoresistive effects are observed for the first time in single-crystalline <0001> WZ InAs nanowires, but negligible effect is found in WZ nanowires with other orientations and nanowires with ZB structures. An ultrafast and reversible electrochemical lithiation of InAs nanowires are observed for the first time. Field effect transistors (FETs) based on MBE-grown InAs nanowires are studied. Importantly, based on nano-manipulation and microlithography, we develop a new method to characterize the same individual InAs nanowires in the FETs by transmission electron microscopy to obtain the atomic-level structures. Our study shows that not only the diameter, but also the crystal structure and the orientation of the InAs nanowires remarkably affect the electronic properties of the FETs, such as the threshold voltage, On/OFF current ratio, on-state current, subthreshold swing and electron mobility, etc. Ohmic contact are obtained for the nanowires with different diameters down to 7 nm.
The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.1016/j.cja.2014.10.009. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy..
Abstract Metal halide perovskites (MHPs) show excellent optoelectronic properties and exhibit great potential applications in optoelectronic devices, such as solar cells (SCs), photodetectors, light-emitting diodes (LEDs), lasers, and so on. Vapor-phase synthesis provides an important way to grow large-scale, high-quality MHP thin films and micro-/nanostructures, exhibiting wide applications in constructing all kinds of optoelectronic devices. In this review, we systematically summarize the growth of perovskite thin film and the nano-/microstructure by vapor-phase synthesis. The detailed classification of vapor-phase synthesis is first introduced, and the effects of the substrates on the growth process are discussed subsequently. Then, the applications of perovskite thin films and micro-/nanostructures grown by vapor-phase synthesis in SCs, photodetectors, LEDs, lasers, and so forth, are discussed in detail. Finally, the conclusions and outlook are presented.
Abstract Low‐temperature‐processed perovskite solar cells (PSCs), which can be fabricated on rigid or flexible substrates, are attracting increasing attention because they have a wide range of potential applications. In this study, the stability of reduced graphene oxide and the ability of a poly(triarylamine) underlayer to improve the quality of overlying perovskite films to construct hole‐transport bilayer by means of a low‐temperature method are taken advantage of. The bilayer is used in both flexible and rigid inverted planar PSCs with the following configuration: substrate/indium tin oxide/reduced graphene oxide/polytriarylamine/CH 3 NH 3 PbI 3 /PCBM/bathocuproine/Ag (PCBM = [6,6]‐phenyl‐C 61 ‐butyric acid methyl ester). The flexible and rigid PSCs show power conversion efficiencies of 15.7 and 17.2%, respectively, for the aperture area of 1.02 cm 2 . Moreover, the PSC based the bilayer shows outstanding light‐soaking stability, retaining ≈90% of its original efficiency after continuous illumination for 500 h at 100 mW cm −2 .
In this work, we propose a novel concept to develop two fluorophores 2-(10 H-phenothiazin-10-yl)thianthrene 5,5,10,10-tetraoxide (PTZ-TTR) and 2-(4-(10 H-phenothiazin-10-yl)phenyl)thianthrene 5,5,10,10-tetraoxide (PTZ-Ph-TTR) showing dual conformations for highly efficient single-emitter white organic light-emitting diodes (WOLEDs). Both molecules exist in two stable conformations. Their nearly orthogonal forms own lower energy levels and show thermally activated delayed fluorescence (TADF) characteristics, whereas their nearly planar conformers possess higher energy levels and show only prompt fluorescence. These dual conformers were exploited for fabricating WOLEDs with complementary emission colors contributed by the two conformations. Moreover, the originally wasted triplet energy on the nearly planar conformation can be transferred to the nearly orthogonal one and then harvested via the TADF channel, realizing full exciton utilization. A PTZ-TTR-based single-emitter device exhibits standard white emission with a CIE coordinate of (0.33, 0.33) and a high color rendering index value of 92. On the other hand, the PTZ-Ph-TTR-based single-emitter device realizes an emission approaching warm white light and a high maximum external quantum efficiency of 16.34%. These results demonstrate an alternative approach for designing high-performance WOLEDs based on single TADF emitters.
Copyrights create long-lived intellectual property in goods ranging from science, literature, and music to news, film and software. The economic effects of copyright, however, are difficult to identify in modern settings. This article exploits an unintended differential increase in copyright length under the UK Copyright Act of 1814 – in favor of books by dead authors – to examine the effects of longer copyright terms on price. We find that a doubling in copyright length was associated with a substantial (roughly 50 percent) increase in the price of books. Additional years of copyright improved publishers’ ability to practice intertemporal price discrimination.
The piezo-phototronic effect utilizes the piezo-polarization charge to modify the energy band diagram at the local interface/junction and manipulate the optoelectronic processes of charge carriers, which have provided a promising approach to improve the performance of photoelectric devices. In this paper, we report on the fabrication of single ultra-fine CdTe nanowire (NW) piezo-phototronic photodetectors (PDs). The structure and morphology of the as-synthesized CdTe NWs is characterized in detail. The result shows that the CdTe NWs have a single crystalline zinc blende structure, with its diameter narrowing to about 20 nm. The flexible Ag-CdTe NW-Ag lateral PDs are prepared on the polyethylene terephthalate substrate, showing a broadband photoresponse from ultraviolet to near infrared (NIR) (325-808 nm). By introducing the piezo-phototronic effect, strain-induced piezoelectric polarization charges effectively enhance the performances of the NIR PDs (808 nm) by 430% in photocurrent and 427% in photoresponsivity. The physical mechanism is carefully investigated by analyzing the energy band diagrams at the local metal–semiconductor interface under mechanical deformations. The ultra-fine structure with a larger piezoelectric coefficient is attributed to the enhancement of photoresponsivity. This investigation demonstrates an efficient prototype of the broad-wavelength piezo-phototronic PD based on the ultra-fine CdTe NWs, which provides an effective route to enhance the performance of optoelectronic devices.
Wavefield manipulation of surface plasmon polaritons (SPPs) is one of the fundamental subjects in nanophtonics. In this paper, based on the analyses of the plasmonic and photonic modes of the L-shaped slit samples with different widths, the dependence of the wavevector, amplitude and phase of the scattered wavefields on the slit width are experimentally determined. The excited plasmonic mode and photonic mode wavelets by arbitrary slit element is analyzed theoretically. Au ring-slits with different widths are also experimented as general slit structure to show the polarized patterns originated from the superimposition of the two modes, and the evolution of total and polarized intensity patterns with the ring-slit widths is studied systematically. The wavefield patterns of the polarization components are also calculated with the obtained components of wavefields and Huygens–Fresnel principle, and results of calculations and experiments are coincident. In addition, the results are validated by performing finite-difference time-domain simulations. The work may enhance the efficiency of slit engineering for SPP pattern manipulations and can be a helpful reference for the fabrication of nano-optics devices.
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