1,721,052 research outputs found
PHOSPHORLESS COLOR TUNING OF LIGHT-EMITTING-DIODES BY RED- EMITTING NANOSTRUCTURED POROUS SILICON POWDER
No full textIn this work, powders of nanostructured porous silicon (NPSp) with strong and broad photoluminescence in the red portion of the spectrum are used as non-toxic phosphors for effectively tuning the color of commercial blue- LEDs from blue to violet, magenta, and red via wavelength conversion. NPSp/polydimethylsiloxane (PDMS) composites consisting of PDMS encapsulating different concentrations of red-emitting NPSp obtained by electro- chemical etching of silicon are prepared and spotted on top of commercial blue-LEDs. Good reliability of the tun- ing process, in terms of NPSp fabrication and concentration, and excellent stability of the tuning color, in terms of LED biasing, are demonstrated by electrical/optical characterization of several NPSp-modified commercial LEDs
Color tuning of light-emitting-diodes by modulating the concentration of red-emitting silicon nanocrystal phosphors
Full text linkLuminescent forms of nanostructured silicon have received significant attention in the context of quantum-confined light-emitting devices thanks to size-tunable emission wavelength and high-intensity photoluminescence, as well as natural abundance, low cost, and non-toxicity. Here, we show that red-emitting silicon nanocrystal (SiN) phosphors, obtained by electrochemical erosion of silicon, allow for effectively tuning the color of commercial light-emitting-diodes (LEDs) from blue to violet, magenta, and red, by coating the LED with polydimethylsiloxane encapsulating different SiN concentrations. High reliability of the tuning process, with respect to SiN fabrication and concentration, and excellent stability of the tuning color, with respect to LED bias current, is demonstrated through simultaneous electrical/optical characterization of SiN-modified commercial LEDs, thus envisaging exciting perspectives for silicon nanocrystals in the field of light-emitting applications
ELECTROMAGNETIC RADIATION EMITTING DEVICE AND MANUFACTURING PROCESS THEREOF
No full textThe present invention relates to an electromagnetic radiation emitting device (LED 140) comprising at least one layer made of semiconductor material suitable for emitting a first electromagnetic radiation centered at a first wavelength and at least one wavelength converter layer (150) coated on said at least one layer made of semiconductor material. The wavelength converter layer is provided for at least partially converting the first electromagnetic radiation so that the resultant electromagnetic radiation is emitted by said emitting device centered at a second wavelength different from said first wavelength, the material (130) of the wavelength converter layer comprising nanostructured silicon (120). Furthermore the present invention relates to a manufacturing process of said device
Dispositivo emettitore di radiazione elettromagnetica, processo di produzione di detto dispositivo ed uso di silicio nano-strutturato per l’emissione di detta radiazione
No full textLa presente invenzione concerne un dispositivo emettitore di radiazione elettromagnetica comprendente almeno uno strato di materiale semiconduttore atto ad emettere una prima radiazione elettromagnetica in una prima lunghezza d’onda ed almeno uno strato convertitore associato a detto almeno uno strato di materiale semiconduttore. Lo strato convertitore è preposto a convertire almeno parzialmente la prima radiazione elettromagnetica in modo che la radiazione elettromagnetica prodotta dal dispositivo emettitore sia emessa in una seconda lunghezza d’onda differente dalla prima lunghezza d’onda, il materiale dello strato convertitore comprendendo silicio
nano-strutturato. La presente invenzione concerne, inoltre, un processo di produzione di detto dispositivo e l’uso di detto silicio nano-strutturato in un dispositivo emettitore per modificarne la sua emissione spettrale. (Fig. 4
Colorful Light-Emitting-Diodes via Modulation of the Concentration of Red-Emitting Silicon Nanocrystal Phosphors
No full textThe research activity into the development of luminescent forms of silicon has now spanned two decades, driven by scientific interest, commercial potential, and technological advancement [1]. It is now well established that silicon crystallites of reduced dimensions, typically below 5 nm, emit light with high efficiency due to quantum confinement effect, with respect to inefficient light emission of bulk crystalline silicon [2]. Canham [2] was the first to demonstrate in 1990 room- temperature photoluminescence from nanocrystallites of silicon (i.e. porous silicon) that were obtained by electrochemical erosion of crystalline silicon in acidic electrolytes. Many other methods were subsequently developed for the synthesis of luminescent nanostructured forms of silicon, including annealing of SiOx powder followed by etching in HF, plasma synthesis, solution reduction of SiCl4, plasma etching of silicon and subsequent thermal oxidation [3-6].
Very recently silicon nanocrystals (SiNs) with high PL quantum yield (about 17%), obtained by low-cost electrochemical erosion of crystalline silicon substrate, has been proposed as non-toxic phosphors for wavelength conversion in ultraviolet/blue LEDs. [7, 8].
Here we show that SiN phosphors with strong and broad photoluminescence in the red portion of the spectrum, obtained by electrochemical erosion of silicon, can be used as non-toxic phosphors for effectively tuning the color of commercial blue-LEDs from blue to violet, magenta, and red via wavelength conversion, by coating the LED with polydimethylsiloxane (PDMS) encapsulating different SiN concentrations [16]. Good reliability of the tuning process, with respect to SiN fabrication and concentration, and excellent stability of the tuning color, with respect to LED operation current, is demonstrated through simultaneous electrical/optical characterization of a number of SiN-modified commercial LEDs.
In spite of the huge research effort that has been paid so far on the use of SiNs for LED applications, the possibility of efficiently tuning the color of LEDs via wavelength-conversion by modultating the concentration of red-emitting SiN phosphors has never been reported.New exciting perspectives in the field of light-emitting applications of SiNs are envisaged by building on these results.
[1] L. Mangolini, Journal of Vacuum Science and TechnologyB 31, 020801 (2013).
[2] L. T. Canham, Applied Physics Letters 57, 1046 (1990).
[3] Shu-Man Liu, Yang Yang, Seiichi Sato, and Keisaku Kimura, Chemistry of Materials 18, 637
(2006).
[4] X. D. Pi, R. W. Liptak, J. Deneen Nowak, N. P. Wells, C. B. Carter, S. A. Campbell, and U.
Kortshagen, Nanotechnology 19, 245601 (2008).
[5] J. Zou, P. Sanelle, K. A. Pettigrew, and S. M. Kauzlarich, Journal of Cluster Science 17, 565
(2006).
[6] S. S. Walavalkar, C. E. Hofmann, A. P. Homyk, M. D. Henry, H. A. Atwate, and A. Scherer,
Nano Letters 10, 4423 (2010).
[14] C.-C. Tu, Q. Zhang, L. Y. Lin, and G. Cao, Optics Express 20, A69 (2011).
[15] C.-C. Tu, J. H. Hoo, K. F. Bohringer, L. Y. Lin, and G. Cao, Optics Letters 37, 4771 (2012). [16] G. Barillaro, L. M. Strambini, Applied Physics Letters 104, 091102 (2014
MICROSISTEMA OPTOFLUIDICO A CRISTALLI FOTONICI E PROCEDIMENTO DI REALIZZAZIONE DELLO STESSO
No full textLa presente invenzione ha per oggetto un microsistema optofluidico a cristalli fotonici ed un procedimento di realizzazione dello stesso del tipo precisato nel preambolo della prima rivendicazione.
Dispositivi optofluidici a cristalli fotonici sono attualmente studiati e proposti per diverse applicazioni, ad esempio telecomunicazioni ottiche, sensori e biosenso- ri, e, più in generale, Lab-on-Chip ed altro ancora
Glass microchannel technology for capillary electrophoresis
No full textThe fabrication process of glass chips for capillary elect rophoresis by means of micromachining is reported. The device is made up of two glass substrates joined by means of thermal fusion bonding. Selective wet etchings were used to define Five microchannels, four for samples injection and one for the separation, while the access holes were obtained with diamond drills. The fabrication process required only one photolithographic step and the thermal fusion bonding did not reduce the uniformity and integrity of the channels. Good results in terms of microchannels shape definition, repeatability and glass surface quality have been obtained
Towards high aspect-ratio MEMS fabrication by silicon electrochemical micromachining technology
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