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Ghulinyan M.,Advanced Photonics and Photovoltaics Group | Guider R.,Johannes Kepler University | Pucker G.,Advanced Photonics and Photovoltaics Group | Pavesi L.,University of Trento
IEEE Photonics Technology Letters | Year: 2011

We report on the realization of a silicon-based microresonator/waveguide coupled system, fully integrated on a silicon chip. The device uses a vertical coupling scheme of the resonator and a buried strip waveguide. We demonstrate that its high optical quality follows from the accurate planarization of the waveguide topography, which is achieved by multiple depositions-and-reflows of a borophosphosilicate glass over strip waveguides. More importantly, we demonstrate wafer-scale mass fabrication of freestanding planar resonators suspended in air and coupled to integrated bus waveguides, as well as controlled selective excitation of different mode families of the resonator. This opens the door for the realization of stable all-integrated complex resonator systems for optomechanical and metrological applications, with the potential to substitute today's intensive use of complicated fiber-taper coupling schemes. © 2011 IEEE.

Sgrignuoli F.,University of Florence | Ingenhoven P.,University of Florence | Pucker G.,Advanced Photonics and Photovoltaics Group | Mihailetchi V.D.,ISC Konstanz | And 5 more authors.
Solar Energy Materials and Solar Cells | Year: 2015

Silicon nanocrystals show a significant shift between the strong absorption in the blue-ultraviolet region and their characteristic red-near-infrared emission as well as space separated-quantum cutting when short wavelength photons are absorbed. These two effects can be used to increase the efficiency of crystalline silicon solar cells. We fabricated high quality interdigitated back-contact crystalline silicon solar cells in an industrial pilot line and coated them with optimized silicon nanocrystals layers in a cost effective way. Here we demonstrate an increase of 0.8% of the power conversion efficiency of the interdigitated back-contact cell by the silicon nanocrystals layer. In addition, we prove that this increase is due to a combination of a better surface passivation, a better optical coating, and of the luminescent downshifting effect. Moreover we demonstrated that the engineering of the local density of photon states, thanks to the Purcell effect, is instrumental in order to exploit this effect. © 2014 Elsevier B.V. All rights reserved.

Jestin Y.,Advanced Photonics and Photovoltaics Group | Pucker G.,Advanced Photonics and Photovoltaics Group | Ghulinyan M.,Advanced Photonics and Photovoltaics Group | Ferrario L.,Bruno Kessler Foundation | And 7 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Materials used as luminescent down shifters (LDS) have to absorb light effectively in the spectral area where solar cells have poor internal quantum efficiency. At the same time these materials have to emit most of the absorbed spectral powers at lower energies where the internal quantum efficiency of the solar cell is close to the maximum. The effects of silicon nanocrystals prepared by thermal treatment of a silicon-rich-oxide (SRO) layer on the efficiency of c-Si cells are investigated in this paper. The SRO layer is characterized by a high photoluminescence peak at around 800 nm. Influence of the active layer on light transmission and on the modification of the optical spectra due to photoluminescence generation has been determined with the help of optical measurements and transfer matrix simulations. The solar cell efficiency for cells with and without down-shifting layer were measured under illumination with AM1.5G solar spectrum and compared with the simulations. Finally, we model the behavior of cells with and without LDS layer showing that a cell with LDS suffers less from bad surface passivation. © 2010 SPIE.

Yuan Z.,University of Trento | Yuan Z.,Jiangsu University | Pucker G.,Advanced Photonics and Photovoltaics Group | Marconi A.,University of Trento | And 6 more authors.
Solar Energy Materials and Solar Cells | Year: 2011

The effects of a Si-rich silicon oxide (SRO) layer containing silicon nanocrystals as photoluminescence down-shifter layer on a conventional Si solar cell were investigated. Two SRO layers with different thicknesses but same composition were deposited on top of Si solar cells by plasma-enhanced chemical vapor deposition and followed by high temperature annealing to precipitate silicon nanocrystals. The SRO layers absorb efficiently high energy photons (especially higher than twice Si bandgap) and emit photons at longer wavelength, which are in turn absorbed by Si. A relative increase of about 14% to the internal quantum efficiency has been observed. © 2010 Elsevier B.V. All rights reserved.

Marconi A.,University of Trento | Anopchenko A.,University of Trento | Pucker G.,Advanced Photonics and Photovoltaics Group | Pavesi L.,University of Trento
Applied Physics Letters | Year: 2011

The power efficiency of silicon nanocrystal light-emitting devices is studied in alternating current (ac) regime. An experimental method based on impedance spectroscopy is proposed. The power efficiency in ac regime is higher than the one measured in direct current before a threshold frequency and decreases significantly for higher frequencies. This decrease is attributed to an increase in electrical power injected at high frequencies and it is directly related to the disordered microscopic structure of the active material. The proposed method can be applied for any kind of device for which it is possible to measure the impedance characteristic. © 2011 American Institute of Physics.

Bianco F.,University of Trento | Fedus K.,University of Trento | Enrichi F.,Coordinamento Interuniversitario Veneto per le Nanotecnologie | Pierobon R.,Coordinamento Interuniversitario Veneto per le Nanotecnologie | And 4 more authors.
Semiconductor Science and Technology | Year: 2012

Micro-Raman scattering experiments were performed on strained silicon waveguides designed for nonlinear optical experiments. Thin stressing silicon nitride (Si 3N 4or SiN x) cladding layers, deposited on a light-guiding silicon core layer, strain silicon to enable χ (2), the second-order nonlinear susceptibility. Different deposition treatments allow varying the applied stress. The resulting strained waveguides are investigated by micro-Raman confocal spectroscopy performed on the waveguide facet. By modelling the measured Raman shifts, the local stress and strain are extracted. Thus, two-dimensional maps of the stress distribution as a function of the SiN x deposition parameters are drawn. A comparison of different samples allows underlying the non-uniformity of resulting strain. © 2012 IOP Publishing Ltd.

Sgrignuoli F.,University of Trento | Paternoster G.,University of Trento | Marconi A.,University of Trento | Ingenhoven P.,University of Trento | And 3 more authors.
Journal of Applied Physics | Year: 2012

A transfer matrix model of a luminescent down-shifter (LDS) layer, consisting of silicon nanocrystals (Si-NCs) embedded in a silicon oxide matrix, on a silicon solar cells is presented. To enhance the efficiency of the silicon solar cell, we propose using a SiO 2/Si-NCs double layer stack, as an anti-reflection-coating (ARC) and as a LDS material. The optical characteristics of this stack have been simulated and optimized as a front surface coating. The cell performances have been simulated by means of a two-dimensional device simulator and compared with the performances of a reference silicon solar cell. We found a 6 relative enhancement of the energy conversion efficiency with respect to the reference cell. We demonstrate that this enhancement results from the lower reflectance and from the down-shifter effect of the Si-NCs activated coating stack. © 2012 American Institute of Physics.

Anopchenko A.,University of Trento | Anopchenko A.,University of Rome La Sapienza | Marconi A.,University of Trento | Marconi A.,RandD Systems S.r.l. | And 6 more authors.
Physica Status Solidi (A) Applications and Materials Science | Year: 2013

In this contribution we give an overview of our development of size-controlled multilayered ensembles of silicon nanocrystals (Si-NCs) for efficient light emitting devices (LEDs). The ensembles of Si-NCs embedded in silicon dioxide are grown by chemical vapour deposition methods and by using standard microelectronic processes. The formation of nanocrystals is monitored by several analytical techniques. Novel LED architectures of nanocrystal ensembles which improve electrical injection and light emission are described. Charge tunnelling in nanosilicon superlattices, light emission efficiency under direct and alternating current injection, and device stability are discussed. Visible light emission from an electroluminescence (EL) device with Si-NCs. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tondini S.,University of Trento | Tondini S.,University of Modena and Reggio Emilia | Pucker G.,Advanced Photonics and Photovoltaics Group | Pavesi L.,University of Trento
Journal of Physics D: Applied Physics | Year: 2015

In this work we study the electroluminescence (EL) from a high efficiency multilayered silicon nanocrystals light emitting diode. The spectral analysis of EL under dc condition shows a spectrally modulated optical emission. Through reflectivity measurements we evaluated the effects of interference on the EL lineshape due to device structure and ascribed the emission to recombination in size dispersed silicon nanocrystals (Si-NCs). By studying the time resolved current-voltage I-V and EL-V, we evidenced that injected carriers are both accumulated separately and concurrently in Si-NCs. At the bias transition the accumulated carriers either are extracted from the gate oxide giving rise to a short current pulse or they diffuse to large Si-NCs giving rise to an EL overshoot which decays with's time constant. © 2015 IOP Publishing Ltd.

Marconi A.,University of Trento | Anopchenko A.,University of Trento | Pucker G.,Advanced Photonics and Photovoltaics Group | Pavesi L.,University of Trento
Semiconductor Science and Technology | Year: 2011

An all-silicon light emitting and detecting device is described here. It is based on a nanocrystalline-silicon light emitting diode (Si-NC LED). The Si-NC LED has up to 0.2% external power efficiency, when forward biased, while it has a photoresponsivity of up to 1 mA W-1 when reverse biased. Therefore, the very same device can be used as a transmitter and receiver node of an optical link. We demonstrate a power loss of 10-3% and a modulation speed of up to 10 kbit s-1 by connecting two Si-NC LEDs by a multimode optical fiber. © 2011 IOP Publishing Ltd.

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