Dr. Benedikt Bläsi Profile

Dr. Benedikt Bläsi

Head of Team at Fraunhofer-Institut für Solare Energiesysteme

SPIE Involvement:

Conference Program Committee | Author

Area of Expertise:

photonic micro- and nanostructures , solar energy systems , micro optics

Websites:

Company Website | Personal Website

Publications (43)

Proceedings Article | 30 May 2022 Presentation

Light trapping gratings for solar cells: an analytical approach to find the best periods

Benedikt Bläsi, Mario Hanser, Adrian Callies, Klaus Jäger, Oliver Höhn

Proceedings Volume PC12150, PC121500C (2022) https://doi.org/10.1117/12.2622897

KEYWORDS: Solar cells, Diffraction gratings, Diffraction, Photovoltaics, Solar energy, Energy efficiency, System on a chip, Statistical analysis, Solar radiation models, Solar radiation

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Grating-based light trapping for solar cells has been investigated since 1989, when Kiess and Morf [1] proposed that concept. Over the years, various grating designs have been explored theoretically and experimentally. Different grating types were investigated, such as linear, crossed and hexagonal gratings. The periods of the investigated gratings typically are in the range between 300 nm and a few micrometers. While for small periods, only a few diffraction orders propagate in the semiconductor at very high angles with respect to the surface normal, gratings with larger periods excite a higher number of orders with a large variety of propagation angles. Gratings could improve the solar cell performance only in a few cases. One example is a III-V//Si triple junction solar cell developed at Fraunhofer ISE [2], in which a crossed grating with 1 µm period contributed to achieve the record efficiency of 35.9%. Although many researchers have investigated gratings for light trapping and have performed various optimizations, the results do not converge to a clear picture. For the optimization, basically two aspects need to be considered: (1) the path length enhancement due to the propagation angle and (2) the escape probability that is connected to the number of diffraction orders which are either trapped or within the escape cone. In this contribution, we present an analytical approach, which takes single path-length enhancement, escape probability, the divergence of solar radiation and the reciprocity of diffraction efficiencies into account. The basic principles of the approach are strongly related to works by Yablonovich [3], Green [4] and Mellor [5]. Based on rather simple assumptions concerning the distribution of the diffraction efficiencies, we show that for crossed and hexagonal gratings there are sweet spots in the period range leading to excellent light trapping, resulting in enhanced near infrared absorptance and photocurrent. One advantage of such a basic model is that fundamental interrelations of the grating parameters can be understood very well. [1] H. Kiess and R. Morf "Light Trapping In Solar Cells And Determination Of The Absorbed Energy By Calorimetry", Proc. SPIE 1149, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion VIII, (12 December 1989); DOI: 10.1117/12.962174. [2] P. Schygulla et al, "Two-Terminal III-V//Si Triple-Junction Solar Cell with Power Conversion Efficiency of 35.9 % at AM1.5g”, accepted for publication in Prog Photovoltaics. [3] E. Yablonovitch (1982): "Statistical ray optics”, J. Opt. Soc. Am. 72 (7), S. 899–907. [4] M. A. Green (2002): "Lambertian light trapping in textured solar cells and light-emitting diodes. analytical solutions”, In: Prog Photovoltaics 10, S. 235–241. [5] A. Mellor, et al (2011): "Upper limits to absorption enhancement in thick solar cells using diffraction gratings”, In: Prog Photovoltaics 19 (6), S. 676–687. DOI: 10.1002/pip.1086.

Proceedings Article | 24 May 2022 Paper

Effect of feature size on the reflective behaviour of the MorphoColorTM concept

Adrian Callies, Andreas Wessels, Andreas Bett, Benedikt Bläsi, Oliver Höhn

Proceedings Volume 12150, 1215003 (2022) https://doi.org/10.1117/12.2620936

KEYWORDS: Reflectivity, Scattering, Reflection, Systems modeling, Refractive index, Diffraction, Solar cells, Computer simulations, Visible radiation

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SPIE Journal Paper | 30 March 2021 Open Access

Impact of the refractive index on coupling structures for silicon solar cells

Laura Stevens, Oliver Höhn, Mario Hanser, Nico Tucher, Claas Müller, Stefan Glunz, Benedikt Bläsi

JPE, Vol. 11, Issue 02, 027001, (March 2021) https://doi.org/10.1117/12.10.1117/1.JPE.11.027001

KEYWORDS: Refractive index, Silicon solar cells, Diffraction gratings, Silicon, Absorption, Diffraction, Solar cells, Interfaces, Systems modeling, Reflectivity

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Proceedings Article | 5 March 2021 Presentation

Coupling structures for silicon solar cells: Impact of the refractive index

Laura Stevens, Oliver Höhn, Mario Hanser, Nico Tucher, Claas Müller, Stefan Glunz, Benedikt Bläsi

Proceedings Volume 11681, 116810U (2021) https://doi.org/10.1117/12.2588836

KEYWORDS: Refractive index, Silicon solar cells, Semiconducting wafers, Diffraction gratings, Crystals, Crystallography

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Proceedings Article | 1 April 2020 Presentation

Optimizing perovskite silicon tandem solar cells for highest efficiency and energy yield (Conference Presentation)

Jan Christoph Goldschmidt, Patricia S. Schulze, Alexander Bett, Özde Kabakli, Kristina Winkler, Ludmila Cojocaru, Martin Bivour, Benedikt Bläsi, Hubert Hauser, Clarissa Hofmann, Armin Richter, Nico Tucher, Leonard Tutsch, Qinxin Zhang, Martin Hermle, Stefan Glunz

Proceedings Volume 11366, 1136603 (2020) https://doi.org/10.1117/12.2559276

KEYWORDS: Perovskite, Silicon, Tandem solar cells, Solar energy, Energy efficiency, Solar cells, Semiconducting wafers, Silicon solar cells, Photovoltaics, Reflection

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Proceedings Article | 1 April 2020 Presentation

Plasmonic and Mie scattering in nanopatterned back reflectors for III–V-on-silicon solar cells (Conference Presentation)

Concetto Eugenio Andrea Cordaro, Nico Tucher, Stefan Tabernig, Hubert Hauser, Oliver Hoehn, Ralph Müller, Benedikt Bläsi, Albert Polman

Proceedings Volume 11366, 1136607 (2020) https://doi.org/10.1117/12.2556088

KEYWORDS: Mie scattering, Silicon, Solar cells, Silver, Plasmonics, Polymethylmethacrylate, Light scattering, Absorption, Scattering, Nanostructures

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Single-junction Si solar cell efficiencies are intrinsically limited to 29.4%. One common strategy to overcome this fundamental issue is to combine multiple semiconductor materials with different bandgaps in a multi-junction configuration so that light is effectively absorbed over a broad range in the solar spectrum. In particular, the combination of a III-V top cell (GaInP/GaAs) that is wafer-bonded to a planar Si bottom cell led recently to an overall record efficiency of 34.1%. The efficiency of this tandem design could be further improved if absorption in the Si cell near the bandgap (1000-1200 nm) is enhanced. Here, we present a nanostructured metallodielectric back reflector placed at the rear of the Si cell that selectively steers incoming light to angles outside the escape cone of the tandem cell. The design is composed of a hexagonal array of Ag nanodisks embedded in a PMMA layer at the rear of the Si cell. Using finite-difference time-domain simulations we optimize pitch, radius, and height of the individual Ag scatterer such that we evenly distribute scattered power over the different diffraction orders. We analyze the scattering behavior in terms of plasmon scattering by the Ag disks and Mie scattering in the dielectric PMMA inclusions. To fully optimize light trapping inside the cell, we choose the geometry such that both 0th-order reflection and plasmonic losses in the Ag nanodisks are minimized. We experimentally demonstrate photonic light trapping by fabricating large scale (2.5×2.5 cm) nanopatterns on untextured Si solar cells. Large-area patterning is performed via Substrate Conformal Imprint Lithography (SCIL) using silica sol-gel as a mask to etch patterns in PMMA, followed by thermal evaporation of Ag. Cross-section SEM shows excellent conformal deposition of Ag inside the patterned nanoholes. Light scattering spectroscopy shows a clearly reduced reflection of the Si cell in the desired wavelength range (1000-1200 nm) due to light trapping, in agreement with simulations. Experimental data of the full nanopatterned III-V/Si tandem geometry will be shown.

Proceedings Article | 3 March 2020 Paper

Modeling and realization of photonic structures for silicon-based tandem solar cells

Oliver Höhn, Hubert Hauser, Nico Tucher, Ralph Müller, Benedikt Bläsi

Proceedings Volume 11275, 1127502 (2020) https://doi.org/10.1117/12.2551034

KEYWORDS: Silicon, Solar cells, Silver, External quantum efficiency, Tandem solar cells, Etching, Nanoimprint lithography, Scattering, Silicon photonics, Silicon solar cells

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Proceedings Article | 5 June 2018 Paper

Photonic structures for III-V//Si multijunction solar cells with efficiency >33%

Benedikt Bläsi, Oliver Höhn, Hubert Hauser, Nico Tucher, Romain Cariou, Jan Benick, Frank Feldmann, Paul Beutel, David Lackner, Gerald Siefer, Stefan Glunz, Andreas Bett, Frank Dimroth, Martin Hermle

Proceedings Volume 10688, 1068803 (2018) https://doi.org/10.1117/12.2307831

KEYWORDS: Silicon, Solar cells, External quantum efficiency, Diffraction gratings, Multijunction solar cells, Gallium arsenide, Silicon solar cells, Wafer bonding, Nanoimprint lithography, Optical simulations, Group III-V semiconductors

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Proceedings Article | 22 May 2018 Paper

Nanoimprinted sol-gel materials for antireflective structures on silicon solar cells

L. Stevens, H. Hauser, O. Höhn, N. Tucher, C. Wellens, R. Jahn, W. Glaubitt, C. Müller, B. Bläsi

Proceedings Volume 10688, 106880B (2018) https://doi.org/10.1117/12.2309935

KEYWORDS: Sol-gels, Reflection, Silicon, Refractive index, Antireflective coatings, Silicon solar cells, Nanoimprint lithography

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Proceedings Article | 22 May 2018 Paper

Advanced module optics of textured perovskite silicon tandem solar cells

Nico Tucher, Oliver Höhn, Benedikt Bläsi, Jan Christoph Goldschmidt

Proceedings Volume 10688, 1068805 (2018) https://doi.org/10.1117/12.2309768

KEYWORDS: Perovskite, Silicon, Tandem solar cells, Absorption, Solar cells, Reflectivity, Interfaces, Systems modeling, Silicon solar cells, Optical properties

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Proceedings Article | 28 April 2017 Presentation + Paper

Interference and nanoimprint lithography for the patterning of large areas

Nico Tucher, Hubert Hauser, Oliver Höhn, Volker Kübler, Christine Wellens, Claas Müller, Benedikt Bläsi

Proceedings Volume 10115, 1011502 (2017) https://doi.org/10.1117/12.2249605

KEYWORDS: Nanoimprint lithography, Optical lithography, Lithography, Solar cells, Display technology, Argon ion lasers, Silicon, Semiconducting wafers, Diffusion, Atomic force microscopy, Etching, Photovoltaics, Silicon solar cells, Light emitting diodes

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Proceedings Article | 29 April 2016 Paper

Nanoparticle scattering for multijunction solar cells

A. Mellor, N. Hylton, O. Höhn, C. Wellens, H. Hauser, T. Thomas, Y. Al-Saleh, N. Tucher, E. Oliva, B. Bläsi, N. Ekins-Daukes, S. Maier

Proceedings Volume 9898, 989809 (2016) https://doi.org/10.1117/12.2228589

KEYWORDS: Solar cells, Nanoparticles, Multijunction solar cells, Electro optical modeling, Light scattering, Antireflective coatings, Solar radiation, Diffusion, Semiconductors, Statistical modeling, Nanoimprint lithography, External quantum efficiency, Aluminum, Reflectivity, Germanium, Metals, Prototyping

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Proceedings Article | 29 April 2016 Paper

Efficient optical analysis of surface texture combinations for silicon solar cells

Nico Tucher, Johannes Eisenlohr, Peter Kiefel, Habtamu Gebrewold, Oliver Höhn, Hubert Hauser, Claas Müller, Jan Christoph Goldschmidt, Benedikt Bläsi

Proceedings Volume 9898, 98980F (2016) https://doi.org/10.1117/12.2228294

KEYWORDS: Geometrical optics, Solar cells, Silicon solar cells, Matrices, Optical analysis, Diffraction gratings, Reflectivity, Matrix multiplication, Light scattering, Scattering, Solar cells, Optical simulations, Interfaces, Silicon, Glasses, Absorption, Optical properties

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Proceedings Article | 29 April 2016 Paper

Rear side gratings for silicon solar cells: efficiency enhancement finally demonstrated

Benedikt Bläsi, Nico Tucher, Johannes Eisenlohr, Benjamin Lee, Jan Benick, Hubert Hauser, Martin Hermle, Jan Christoph Goldschmidt

Proceedings Volume 9898, 98980A (2016) https://doi.org/10.1117/12.2228713

KEYWORDS: Silicon solar cells, Solar cells, Diffraction gratings, Nanoimprint lithography, Absorption, Modeling, Near infrared, External quantum efficiency, Silicon, Amorphous silicon

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Proceedings Article | 27 April 2016 Paper

Large area patterning using interference and nanoimprint lithography

B. Bläsi, N. Tucher, O. Höhn, V. Kübler, T. Kroyer, Ch. Wellens, H. Hauser

Proceedings Volume 9888, 98880H (2016) https://doi.org/10.1117/12.2228458

KEYWORDS: Fabrication, Light sources and illumination, Micro optics, Argon ion lasers, Double patterning technology, Silicon, Diffraction gratings, Electron beam lithography, Semiconducting wafers, Etching

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Proceedings Article | 23 September 2015 Paper

Optical properties of textured sheets: an efficient matrix-based modelling approach

Nico Tucher, Johannes Eisenlohr, Peter Kiefel, Oliver Höhn, Hubert Hauser, Marius Peters, Claas Müller, Jan Goldschmidt, Benedikt Bläsi

Proceedings Volume 9630, 96300G (2015) https://doi.org/10.1117/12.2191316

KEYWORDS: Geometrical optics, Solar cells, Optical properties, Reflectivity, Silicon, Optical simulations, Matrices, Reflectors, Modeling, Wafer-level optics

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SPIE Journal Paper | 29 July 2015 Open Access

Development of nanoimprint processes for photovoltaic applications

Hubert Hauser, Nico Tucher, Katharina Tokai, Patrick Schneider, Christine Wellens, Anne Volk, Sonja Seitz, Jan Benick, Simon Barke, Frank Dimroth, Claas Müller, Thomas Glinsner, Benedikt Bläsi

JM3, Vol. 14, Issue 03, 031210, (July 2015) https://doi.org/10.1117/12.10.1117/1.JMM.14.3.031210

KEYWORDS: Nanoimprint lithography, Silicon, Solar cells, Photovoltaics, Etching, Semiconducting wafers, Absorption, Optical lithography, Silicon solar cells, Plasma etching

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Proceedings Article | 19 March 2015 Paper

Development of NIL processes for PV applications

H. Hauser, N. Tucher, K. Tokai, P. Schneider, Ch. Wellens, A. Volk, S. Barke, C. Müller, Thomas Glinsner, B. Bläsi

Proceedings Volume 9423, 94230U (2015) https://doi.org/10.1117/12.2085754

KEYWORDS: Nanoimprint lithography, Silicon, Solar cells, Etching, Semiconducting wafers, Photovoltaics, Plasma etching, Optical lithography, Absorption, Silicon solar cells

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Proceedings Article | 15 May 2014 Paper

Study of plasmonic nanoparticle arrays for photon management in solar cells

Benedikt Bläsi, Sabrina Jüchter, Sarah-Katharina Meisenheimer, Oliver Höhn, Hubert Hauser, Christine Wellens, Thomas Fix, Ulrich Schwarz

Proceedings Volume 9140, 91400W (2014) https://doi.org/10.1117/12.2052244

KEYWORDS: Silicon, Particles, Absorption, Nanoparticles, Silver, Glasses, Plasmonics, Solar cells, Polarization, Nanoimprint lithography

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Proceedings Article | 15 May 2014 Paper

Novel light trapping concepts for crystalline silicon solar cells using diffractive rear side structures

J. Eisenlohr, N. Tucher, Alexander Bett, H. Hauser, M. Graf, J. Benick, J. Goldschmidt, B. Bläsi, M. Hermle

Proceedings Volume 9140, 91400C (2014) https://doi.org/10.1117/12.2051667

KEYWORDS: Absorption, Solar cells, Silicon, Amorphous silicon, Diffraction gratings, Optical spheres, Crystals, Diffraction, Antireflective coatings, Dielectrics

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Proceedings Article | 15 May 2014 Paper

The photonic solar cell: system design and efficiency estimations

Oliver Höhn, Tobias Kraus, Ulrich Schwarz, Benedikt Bläsi

Proceedings Volume 9140, 91400B (2014) https://doi.org/10.1117/12.2051322

KEYWORDS: Solar cells, Mirrors, Photonic crystals, Absorption, Gallium arsenide, Crystals, Photonics systems, Dielectrics, Solar energy systems, Thin film solar cells

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Proceedings Article | 25 September 2013 Paper

Photonic structures for enhanced upconversion

B. Herter, S. Wolf, S. Fischer, J. Gutmann, B. Bläsi, J. Goldschmidt

Proceedings Volume 8824, 88240A (2013) https://doi.org/10.1117/12.2023845

KEYWORDS: Upconversion, Absorption, Luminescence, Quantum efficiency, Photons, Refractive index, Solar energy, Ions, Silicon, Energy transfer

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Proceedings Article | 12 October 2012 Paper

Nano-imprinted rear-side diffraction gratings for absorption enhancement in solar cells

Alexander Mellor, Hubert Hauser, Aron Guttowski, Christine Wellens, Benedikt Bläsi, Ignacio Tobías, Antonio Martí, Antonio Luque

Proceedings Volume 8471, 84710O (2012) https://doi.org/10.1117/12.929034

KEYWORDS: Absorption, Silicon, Reflectors, Solar cells, Diffraction gratings, Semiconducting wafers, Aluminum, Silica, Nanoimprint lithography, Lithography

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