Ramón Alcubilla González

Mechanical properties of Al2O3 inverse opals by means of nanoindentation

In order to understand the mechanical behaviour of Al2O3 inverse opals, nanoindentation techniques have been implemented in material layers with three different microstructures, in terms of hollow or polystyrene spheres, with Al2O3 shells of distinct wall thickness. Different indenter tip geometries as well as contact loading conditions have been used, in order to induce different stress field and fracture events to the layers. Field emission scanning electron microscopy and focused ion beam have been employed to understand accommodation of plastic deformation induced during the indentation process. Results show that materials with polystyrene spheres exhibit higher hardness and modulus under sharp indentation, and cracking resistance under spherical indentation. Furthermore, deformation is discerned to be mainly governed by the rotation of the microspheres. In the case of the inverse opals made of hollow spheres, the main deformation mechanisms activated under indentation are the rearrangement and densification of them

Thin IBC c-Si Solar Cells Based on Conventional Technologies

Reducing the wafer thickness for c-Si solar cell fabrication is an effective approach for cost-savings. Interdigitated Back Contacts (IBC) technology is a promising candidate to be applied to thin c-Si substrates due to its potential to facilitate thin device processing: thin c-Si solar cell could be processed attached to a glass with its rear surface, where all the contacts are to be defined, still accessible. The understanding of thin IBC c-Si solar cell performance has great significance in guiding the design of such devices. In this work, we explore the performance of thin IBC c-Si solar cells by both 3D TCAD device simulations and experimental fabrication based on conventional technology developed in our research group. On one hand, an optical model is proposed using 2D ray tracing method whose results are applied to 3D ATLAS TCAD simulator which is used to simulate the electrical performance of the devices. As a result, efficiencies in the range of 20 % are expected for substrates of 10-20 µm without changing our technology. On the other hand, a ~30 µm IBC solar cell is fabricated by thinning down a previously developed IBC c-Si solar cell on conventional thick high quality substrates demonstrating a 12.1% of efficiency. The front surface passivation provided by Al2O3 is deduced by comparing with the simulation results revealing a front surface recombination velocity of about 1500 cm/s.

From random to order: Colloidal crystals on non-flat surfaces

© 2016 Elsevier B.V. All rights reserved. nThis paper introduces the possibility to produce 1-2 cm2 and tens of layers colloidal crystals on different non-flat surfaces by means of electrospray deposition. Two different types of crystalline silicon surfaces were tested: nanostructured

2D/3D Simulations of black-silicon interdigitated back-contacted c-si(n) solar cells

Black silicon (b-Si) reduces drastically light reflectance in the front side of c-Si solar cells to values near zero for the whole absorbed solar spectrum. In this work, we apply 2D and 3D simulations to explore the efficiency limits of interdigitated back-contacted c-Si(n) solar cells with line or point contacts respectively, using ALD Al2O3 passivated b-Si in the front surface. Realistic physical and technological parameters involved in a conventional oven-based fabrication process are considered in the simulations, especially those related to surface recombination on the b-Si as well as high doped p+/n+ strip regions. One important issue is the temporal stability of surface passivation on b-Si surfaces. In this work experimental long-term b-Si surface passivation data after two years and its impact on cell performance are studied. Simulations demonstrate initial and final photovoltaic efficiencies over 24.6% and 23.2% respectively for an emitter coverage of 80% independently of the cell contact strategy. A photocurrent loss about 1.3 mA/cm2 occurs when surface recombination velocity at the b-Si surfaces degrades from 6 cm/s to a final value of 28 cm/s.