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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.

Anopchenko A.,University of Trento | Marconi A.,University of Trento | Wang M.,University of Trento | Pucker G.,Advanced Photonics and Photovoltaics | And 2 more authors.
Applied Physics Letters | Year: 2011

We propose a simple way to engineer the energy band gap of an ensemble of silicon nanocrystal (Si-NC) embedded in SiO2 via thickness/ composition profiling of Si-NC multilayers. By means of a complementary metal-oxide-semiconductor compatible process, light emitting diodes (LEDs) which incorporate graded energy gap Si-NC multilayers in the active region have been grown. Electrical and optical properties of these graded Si-NC LEDs demonstrate the ability of the proposed method to tailor the optoelectronic properties of Si-NC devices. © 2011 American Institute of Physics.

Mukhiya R.,Indian Institute of Technology Kharagpur | Bagolini A.,Microtechnologies Laboratory | Bhattacharyya T.K.,Indian Institute of Technology Kharagpur | Lorenzelli L.,Microtechnologies Laboratory | Zen M.,Microtechnologies Laboratory
Microelectronics Journal | Year: 2011

In the present work, most common compensation structures (〈1 1 0〉 squares and 〈1 0 0〉 bars) have been used for convex corner compensation with 25 wt% TMAH-water solution at 90±1 °C temperature. Etch flow morphology and self-align properties of the compensating structures have been investigated. For 25 wt% TMAH water solution {3 1 1} plane is found to be responsible for corner undercutting, which is the fast etch plane. Etch-front-attack angle is measured to be 24°. Generalized empirical formulas are also discussed for these compensation structures for TMAH-water solution. 〈1 1 0〉 square structure protects mesa and convex corner and is the most space efficient compared to other compensation structures, but unable to produce perfect convex corner as 〈1 0 0〉 bar type structures. Both the 〈1 0 0〉 bar structures provide perfect convex corners, but 〈1 0 0〉 wide bar structure is more space efficient than the 〈1 0 0〉 thin bar structure. Implications of these compensation structures with realization of accelerometer structure have also been discussed. A modified quad beam accelerometer structure has been realized with these compensation structures using 25 wt% TMAH. © 2010 Elsevier Ltd. 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.,Microtechnologies Laboratory | 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.

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