Monodisperse Al-Doped ZnO/Perovskite Nanocapsule.

We developed monodisperse ZnO nanocapsules and atmospheric N plasma was used to develop a ZnO-organic nanocomposite. To test the seal of the ZnO nanocapsule, the halide perovskite CH3NH3PbBr3 was used as the filler. Al atoms were doped into ZnO nanorods to increase the conductivity of ZnO nanorods. A green emission peak located at 535 nm was observed in the nanocapsules with a 410 nm excitation because of the free-exciton recombination of CH3NH3PbBr3. The Al-doped ZnO (AZO)/CH3NH3PbBr3 nanocapsules was further tested under using a three-electrode photoelectrochemistry cell. AZO/CH3NH3PbBr3 nanocapsule arrays yield an elevated photocurrent of approximately 0.2 mA/cm2 at 1 V versus Ag/AgCl under air mass 1.5 (AM 1.5), almost 1.5 times larger than that of the AZO nanorod arrays. The photo-current stability of AZO/CH3NH3PbBr3 nanocapsule arrays photoelectrode is better than that of AZO nanorod arrays under a repeated on/off light test. This confirmed that the AZO/CH3NH3PbBr3 nanocapsules had been successfully sealed and that the degradation of CH3NH3PbNBr3 was thus dramatically reduced. Our study yields a novel platform for nanoscale optical and optoelectronic devices or for delivery of highly toxic drugs.

Transparent conductive oxide layer with monolayer closed-pack Al-doped ZnO spheres and their application to a-Si thin-film solar cells.

We report a new (to the best of our knowledge) transparent conductive oxide (TCO) layer with a monolayer of closed-pack Al-doped ZnO (AZO) spheres partly embedded in an AZO thin film. The average transmittance and haze ratio in the wavelength range of 380-800 nm achieves 65% and 55%, respectively, when AZO spheres with a diameter of 500 nm are embedded in a thickness of 240 nm AZO thin films. The a-Si thin-film solar cell with a regular p-i-n TCO structure is demonstrated. Under air mass 1.5 global illumination, conversion efficiencies of 5.6%, a fill factor of 0.55, V(oc) of 0.81 V, and a J(sc) of 2.44 mA/cm² are obtained. The Letter helps us to open up potential applications of a new TCO in advanced solar cells and light-emitting diodes.

Temperature dependence of silver nanostructure for surface enhanced Raman scattering application.

We study the fabrication and application of the fractal silver nanostructure using an electrochemical process. Scanning electron microscope and high resolution transmission electron microscope images show the morphology of silver nanostructure can be well controlled via the various reaction times. The surface enhanced Raman scattering of 10 microM aqueous Rhodamine 6G (R6G) solutions conducted in as-fabricated silver nanostructure achieved an enhancement factor approximately 10(5) at room temperature. Meanwhile, an approximately 10(4) enhancement factor of SERS signal can be kept under 200 degrees C in present study. This study can help us to integrate the nano-metals and nano-particles for advanced nano devices.

Morphological variation and Raman spectroscopy of ZnO hollow microspheres prepared by a chemical colloidal process.

The morphological variation of ZnO hollow miscrospheres was achieved via a two-step chemical colloidal process. The products were investigated by scanning electron microscopy, high-resolution transmission electron microscopy, Raman scattering spectroscopy, and photoluminescence spectroscopy. A possible evolution mechanism of the ZnO hollow microspheres was discussed. The lattice distortion of ZnO hollow microspheres was found on the edge of the surface. Raman spectra reveal that the E(2)(high) mode of ZnO hollow microspheres is observed at 432 cm(-1). A Raman shift of 5 cm(-1) had taken place compared with the original form of the ZnO microsphere. This study helps us to understand further the structural properties of ZnO hollow microspheres synthesized by a chemical colloidal process.

Haze ratio enhancement using a closely packed ZnO monolayer structure.

A ZnO thin-film that comprised a ZnO monolayer close-packed structure embedded in ZnO sol-gel was fabricated. The structure contained ZnO spheres of various sizes. At normal incidence, the mean optical transmittance of the thin-film was 60% in the visible region when the structure contained spheres with a diameter of 300 nm. An average haze ratio of 80% was obtained from the thin-film when the structure was formed using 500 nm-diameter spheres. The thin-film exhibits broad-band transparency and a high haze ratio. It can be used as a light-trapping structure in an ultrathin solar cell.

1x2 Multimode interference couplers based on semiconductor hollow waveguides formed from omnidirectional reflectors.

A 1x2 hollow multimode interference (MMI) coupler based on semiconductor hollow waveguides formed from omnidirectional reflectors (SHOW-ODR) is demonstrated. The device has a shorter coupling length than a conventional silicon-on-insulator MMI coupler. A 2 dB uniformity was achieved at operating wavelengths between 1520 and 1562 nm. The device exhibited a weak polarization dependence in the TE and TM modes.

Semiconductor hollow optical waveguides formed by omni-directional reflectors.

In this study, a hollow optical waveguide with omni-directional reflectors in silicon-based materials was design, fabricated and characterized. By using dry etching technique, plasma-enhanced chemical vapor deposition for Si/SiO2 thin films and covering another wafer with omni-directional reflector together, the waveguides can be formed with an air core of 1.2microm x 1.3microm. A uniform propagation loss of the waveguide to be around 1.7dB/cm for C+L band was found for the TE and TM modes. Polarization-independent hollow optical waveguides were obtained with the hollow waveguide structure.