Semitransparent monocrystalline solar cells manufactured by laser cutting and anisotropic etching
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TECHNICAL PAPER
Semitransparent monocrystalline solar cells manufactured by laser cutting and anisotropic etching ´ rpa´d Fo¨ldva´ry • Ja´nos Mizsei Enik} o Ba´ndy • A
Received: 12 July 2012 / Accepted: 27 December 2012 / Published online: 8 January 2013 Ó Springer-Verlag Berlin Heidelberg 2013
Abstract This paper presents two possible technologies used to manufacture semitransparent monocrystalline building integrated solar cells: laser cutting and anisotropic etching. Nd:YAG 1,064 nm laser cut sidewalls are rough and contain molten residues, resulting in shunts across the through-holes confirmed by I–V characteristic measurement and reverse bias measurement results. Tetramethylammonium hydroxide etched edges are uniform with smooth sidewalls. Carrier lifetime and Kelvin probe measurements reveal the flaws occurring in the two technologies.
1 Introduction Solar electricity using photovoltaic (PV) technology is the direct generation of electricity from sunlight. PV modules work silently with no moving parts, minimal maintenance and no pollutant emissions. PV is one of the fastest growing sectors of the renewable energy industry. The market is driven by concerns about environmental awareness of climate-change mitigation and local air quality, as well as national energy security issues and the rising cost of fossil fuels. Building integrated PV (BIPV) implies an application of PV where the system, as well as having the function of
´ . Fo¨ldva´ry J. Mizsei E. Ba´ndy (&) A Department of Electron Devices, Budapest University of Technology and Economics, Magyar tudo´sok ko¨ru´tja 2, Budapest 1117, Hungary e-mail: [email protected] ´ . Fo¨ldva´ry A e-mail: [email protected] J. Mizsei e-mail: [email protected]
producing electricity, also takes on the role of a building element. Different facade systems where PV panels can be applied are shading, rain screen, stick system, curtain walls, double-skin facades, atria or canopies, glazing systems (Roberts and Guariento 2009). Several semitransparent PV technologies are suitable for facade and solar window applications: thin film solar cells, amorphous solar cells and crystalline solar cells with higher efficiency (Miyazaki et al. 2005; Chau et al. 2010). Solutions available on the market for crystalline see-through solar cell development contain laser cutting, mechanical grinding and dicing procedures. Sunways AG has developed crystalline transparent cells by means of an innovative laser production process, which cuts the square recesses and their cells achieve efficiencies up to 13.8 % besides a transmittance of 10 % (German Solar Energy Society 2008). Widespread laser silicon machining tasks are solved with pulsed Nd:YAG or CO2 laser usage. In conventional laser technology the material is molten by focussed laser beam and expelled from the cut by a gas stream. Remelting processes obviously occur at the cut surface areas, which result in stress-induced cracks in the boundary layer and parasitic shunts can be formed between the front and back sides of the cell (Heikenw
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