Amorphous silicon

About: Amorphous silicon is a research topic. Over the lifetime, 26777 publications have been published within this topic receiving 423234 citations.

Plasmonic and silicon spherical nanoparticle antireflective coatings.

Abstract: Over the last decade, plasmonic antireflecting nanostructures have been extensively studied to be utilized in various optical and optoelectronic systems such as lenses, solar cells, photodetectors, and others. The growing interest to all-dielectric photonics as an alternative optical technology along with plasmonics motivates us to compare antireflective properties of plasmonic and all-dielectric nanoparticle coatings based on silver and crystalline silicon respectively. Our simulation results for spherical nanoparticles array on top of amorphous silicon show that both silicon and silver coatings demonstrate strong antireflective properties in the visible spectral range. For the first time, we show that zero reflectance from the structure with silicon coatings originates from the destructive interference of electric- and magnetic-dipole responses of nanoparticle array with the wave reflected from the substrate, and we refer to this reflection suppression as substrate-mediated Kerker effect. We theoretically compare the silicon and silver coating effectiveness for the thin-film photovoltaic applications. Silver nanoparticles can be more efficient, enabling up to 30% increase of the overall absorbance in semiconductor layer. Nevertheless, silicon coatings allow up to 64% absorbance increase in the narrow band spectral range because of the substrate-mediated Kerker effect, and band position can be effectively tuned by varying the nanoparticles sizes.

Evidence of light-emitting amorphous silicon clusters confined in a silicon oxide matrix

Abstract: Amorphous silicon oxide thin films were prepared by the coevaporation technique in ultrahigh vacuum. Different compositions were obtained by changing the evaporation rate of silicon. The samples were then annealed to different temperatures up to 950 °C. The composition and the structure were investigated using energy dispersive x-ray spectroscopy, infrared absorption measurements, and Raman spectroscopy. This study attests the presence of amorphous silicon clusters in a silicon oxide matrix. Optical transmission measurements were performed and interpreted in the field of the composite medium theory. The obtained results are in good agreement with the presented structural model. The photoluminescence in the red-orange domain was studied in relation with the structure. The correlation between the photoluminescence energy and intensity and the structure shows that the light emission originates from the silicon clusters embedded in the silicon oxide matrix. Moreover the dependence of the photoluminescence energy with the silicon volume fraction suggests the origin of the light emission could be due to a quantum confinement effect of carriers in the amorphous silicon clusters.

Solar cell efficiency enhancement via light trapping in printable resonant dielectric nanosphere arrays

Abstract: Resonant dielectric structures are a promising platform for addressing the key challenge of light trapping in thin-film solar cells. We experimentally and theoretically demonstrate efficiency enhancements in solar cells from dielectric nanosphere arrays. Two distinct amorphous silicon photovoltaic architectures were improved using this versatile light-trapping platform. In one structure, the colloidal monolayer couples light into the absorber in the near-field acting as a photonic crystal light-trapping element. In the other, it acts in the far-field as a graded index antireflection coating to further improve a cell which already included a state-of-the-art random light-trapping texture to achieve a conversion efficiency over 11%. For the near-field flat cell architecture, we directly fabricated the colloidal monolayer on the device through Langmuir–Blodgett deposition in a scalable process that does not degrade the active material. In addition, we present a novel transfer printing method, which utilizes chemical crosslinking of an optically thin adhesion layer to tether sphere arrays to the device surface. The minimally invasive processing conditions of this transfer method enable the application to a wide range of solar cells and other optoelectronic devices. False-color SEM image of an amorphous silicon solar cell with resonant spheres on top.

Method for producing a roughened surface capacitor

Abstract: A new method to produce a microminiturized capacitor having a roughened surface electrode is achieved. The method involves depositing a first polycrystalline or amorphous silicon layer over a suitable insulating base. The silicon layer is either in situ heavily, uniformly doped or deposited undoped and thereafter heavily doped by ion implantation followed by heating. The structure is annealed at above about 875° C. to render any amorphous silicon polycrystalline and to adjust the crystal grain size of the layer. The polysilicon surface is no subjected to a solution of phosphoric acid at a temperature of above about 140° C. to partially etch the surface and cause the uniformly roughened surface. A capacitor dielectric layer is deposited thereover. The capacitor structure is completed by depositing a second thin polycrystalline silicon layer over the capacitor dielectric layer.