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Laser structuring of solar glasses for light management

Short and ultra-short laser pulses allow for a flexible and innovative nano-structuring of solar glasses. The aim of these nano-structures is, for example, to provide special growth conditions for thin film solar cells leading to an increase of the solar cell efficiency or at least to an optimization of the production process. In addition, the nano-structured surfaces should provide light trapping abilities. Laser pulses in the range of a few nano-seconds from a Nd:YAG laser were used to nanostructure glass plates with dimensions of 5 cm × 5 cm. Two different laser wavelengths were evaluated, namely 355 nm and 532 nm. The nano-structures analyzed for their light trapping abilities were (i) a 1D-grid structure consisting of many fine, parallel and equally spaced grooves and (ii) a 2D-grid structure. Transmission and reflection measurements showed that the untreated solar glass has a transmittance of 92% in the spectral range from 375 nm to 850 nm; the glass showed no significant light scattering (less than 1%). Laser structuring, however, leads to a significant increase in the forward scattering whereas the total transmittance remains almost unchanged. In the case of the 532 nm laser structuring, the forward scattering of the 1D- and the 2D-grid structure could be increased to more than 4% and 18%, respectively, for the spectral range from 375 to 850 nm. The effect of the 355 nm laser structuring was significantly higher; 45% and 65% forward scattering could be achieved for the 1D- and 2D-grid structure, respectively. The total reflectance is approximately 8% for the 532 nm laser structuring, while it is approximately 16% for 355 nm. Both structures revealed the typical behavior of an optical grating.