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Via the integration of nanocomposites comprising I-III-VI semiconductor quantum dots (QDs) decorated onto a single SnO2 nanowire (NW), we successfully fabricate an ultrahigh-sensitivity and wide spectral-response photodetector. Under the illumination of He-Cd laser (325 nm) with the photon energy larger than the band gap of SnO2 nanowire, remarkably, an ultrahigh photocurrent gain up to 2.5 × 10(5) has been achieved, and an enhancement factor can reach up to 700% (cf. bare SnO2 NW) as light illumination onto the wire with an excitation intensity of 15 W/m(2). Also, a high gain value up to 1.3 × 10(5) is attained with the excited photon energy (488 nm) smaller than the band gap of SnO2 nanowire. Several key factors contribute to ultrahigh photocurrent gain and wide spectral response. First, the decorated quantum dot processes an inherent nature of a large absorption coefficient above its band gap. Furthermore, the single SnO2 nanowire provides an excellent conduction path for the photogenerated carriers as well as bears a large surface-to-volume ratio so that the coupling strength with quantum dots can be greatly enhanced. Most importantly, the spatial separation of photogenerated electrons and holes can be easily achieved due to the charge transfer arising from a type II band alignment between QDs and SnO2 NW. This work thus demonstrates a new approach in which by selectively decorating suitable QDs the photocurrent gain of SnO2 NWs can be greatly enhanced and extended to a wide spectral range of photoresponse previously inaccessible, providing a very useful guideline to create cheap, nontoxic, and highly efficient photodetectors.

A multicolor infrared photodetector was realized with two superlattices separated by a blocking barrier. The photoresponse is switchable between 7.5–12 and 6–8.5 μm by the bias polarity, and is also tunable by the bias magnitude in each wavelength regime. In addition, our detector exhibits advantages including little temperature dependence of the spectral response and the same order of responsivity in the two wavelength regimes. The measured peak responsivities in the two regimes are 117 mA/W at 9.8 μm under 1 V and 129 mA/V at 7.4 μm under −0.8 V, respectively. Also, the detectivities are comparable with the conventional multistack detector. The zero background peak detectivities are 2.3×1010 cm Hz0.5/W at 50 K and 9.8 μm under 0.7 V, and 8.7×1010 cm Hz0.5/W at 70 K and 7.4 μm under −0.7 V.

The resonant coupling between cadmium-free I-III-VI2 group quantum dots (QDs) and metal nanostructures has been investigated. Via a SiO2-packaging synthetic procedure, the emission intensity of green ZCIS/ZnS QDs can be greatly enhanced by three times through the localized surface plasmon of Au nanoparticles. Moreover, the bandwidth of the emission spectrum can be narrowed by 17 nm, and the resultant quantum yield is more than 50% which sets up the highest reported value up today for green I-III-VI2 QDs. Our strategy for the improved characteristics of emission spectrum may open a facile alternative for the development of cadmium-free QD light emitting diodes and other optoelectronic devices.

We report controllable coupling between exciton and localized surface plasmon in a liquid crystal device consisting of gold nanoparticles and CdSe quantum dots. Through an external electric voltage, the emission wavelength of quantum dots can be manipulated. The underlying mechanism is based on the fact that by changing the dielectric index of liquid crystal with an external bias, the surface plasmon frequency of metal nanoparticles can be adjusted. It is therefore possible to control the energy difference between exciton and surface plasmon resonance, and hence to change their coupling strength. Our strategy may open up a possible route for the development of smart optoelectronic devices with tunable emission color.

Double side light emission devices based on p-NiO/n-ZnO nanowire heterojunctions have been fabricated on indium tin oxide substrate by radio frequency magnetron sputtering combined with hydrothermal process. According to the energy band alignment, the detected broad visible and narrow ultraviolet electroluminescence arise from defect and band edge transitions in ZnO nanowires, respectively. The unique property of the double side emission is due to the nature of the large band gap of NiO film. It provides a good opportunity for the emission of a light emitting device with different colors on the top and back sides, simultaneously.