Si quantum dots (QDs) were formed by thermal annealing the hydrogenated amorphous silicon carbide films (a-SiCx:H) with different C/Si ratio x, which were controlled by using a different gas ratio R of methane to silane during the deposition process. By adjusting x and post annealing temperature, the QD size can be changed from 1.4 to 4.2 nm accordingly, which was verified by the Raman spectra and transmission electron microscopy images. Size-dependent electroluminescence (EL) was observed, and the EL intensity was higher for the sample containing small-sized Si QDs due to the quantum confinement effect (QCE). The EL peak energy as a function of the Si QDs size was in good agreement with a modified effective mass approximation (EMA) model. The calculated finite barrier potential of the Si QDs embedded in SiC matrix is 0.4 and 0.8 eV for conduction and valence band, respectively. Moreover, the current-voltage properties and the linear relationship between the integrated EL intensity and injection current indicate that the carrier transport is dominated by Fowler–Nordheim tunneling and the EL mechanism is originated from the bipolar recombination of electron-hole pairs at Si QDs. Our results demonstrate Si QDs embedded in amorphous SiC matrix has the potential application in Si-based light emitting devices and the third-generation solar cells.

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In recent years, many research groups have synthesized ultra-thin silver nanowires (AgNWs) with diameters below 30 nm by employing Cl− and Br− simultaneously in the polyol process. However, the yield of AgNWs in this method was low, due to the production of Ag nanoparticles (AgNPs) as an unwanted byproduct, especially in the case of high Br− concentration. Here, we investigated the roles of Cl− and Br− in the preparation of AgNWs and then synthesized high aspect ratio (up to 2100) AgNWs in high yield (>85% AgNWs) using a Cl− and Br− co-mediated method. We found that multiply-twinned particles (MTPs) with different critical sizes were formed and grew into AgNWs, accompanied by a small and large amount of AgNPs for the NaCl and NaBr additives, respectively. For the first time, we propose that the growth of AgNWs of different diameters and yields can be understood based on the electron trap distribution (ETD) of the silver halide crystals. For the case of Cl− and Br− co-additives, a mixed silver halide crystal of AgBr1−xClx was formed, rather than the AgBr/AgCl mixture reported previously. In this type of crystal, the ETD is uniform, which is beneficial for the synthesis of AgNWs with small diameter (30~40 nm) and high aspect ratio. AgNW transparent electrodes were prepared in air by rod coating. A sheet resistance of 48 Ω/sq and transmittance of 95% at 550 nm were obtained without any post-treatment.

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Silicon nanowires (SiNWs) have attracted increasing attention for their enhanced light harvesting and large junction area of photovoltaic devices compared to planar silicon wafers. However, high surface recombination velocity deteriorates the photovoltaic performance of the SiNW-based solar cells. Therefore, a passivation step is necessary to avoid this effect. Here, a small organic molecule, diallyl disulfide (DADS), has been employed to passivate the surface of SiNWs. This passivation process was carried out under UV illumination at room temperature. Covalent Si–C bonds were formed between DADS and the Si surface, which was experimentally proven to reduce the surface recombination of photogenerated carriers. Compared with cells employing oxide- or hydrogen-passivated SiNWs, the power conversion efficiency of devices employing DADS-passivated SiNWs was 7.2%, which was improved by a factor of 3.8 and 1.6, respectively. Moreover, the solar cell using DADS-passivated SiNWs exhibited good stability in air. The S-shaped current–voltage curves were not observed because of the high oxidation resistance of the DADS-modified surface. This simple and effective UV-initiated passivation procedure with DADS can lower the cost and improve the photovoltaic performance of SiNW-based solar cells.

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a - Si : H ∕ Si O 2 multilayers prepared by plasma-enhanced chemical-vapor deposition exhibit a luminescence band around 760nm, which is quenched after a dehydrogenation process. Subsequent hydrogen plasma annealing (HPA) treatments are carried out, and the luminescence is then recovered. The effects of HPA are investigated as functions of hydrogen annealing time and temperature. Fourier transform infrared spectroscopy and Raman-scattering spectroscopy are used to study the change of the microstructures and bonding configurations due to the HPA treatments. It is indicated that the atomic hydrogen cannot only diffuse into the film to reduce the density of nonradiative recombination centers but can also relax the film network and improve the microstructure order of the a-Si:H sublayers. All these factors are believed to contribute to the recovery of the luminescence signals of the a-Si:H∕SiO2 multilayers.

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