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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. Source


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. Source


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. Source


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. Source


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. Source

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