Patented nanostructure for solar cells: Rough optics, smooth surface

The nanostructure for capturing light is imprinted on silicon oxide (blue) and then "levelled" with titanium oxide (green). The result is an optically rough but smooth layer on which crystalline silicon can be grown.

The nanostructure for capturing light is imprinted on silicon oxide (blue) and then "levelled" with titanium oxide (green). The result is an optically rough but smooth layer on which crystalline silicon can be grown. © HZB

Thin-film solar cells made of crystalline silicon are inexpensive and achieve efficiencies of a good 14 percent. However, they could do even better if their shiny surfaces reflected less light. A team led by Prof. Christiane Becker from the Helmholtz-Zentrum Berlin (HZB) has now patented a sophisticated new solution to this problem.

"It is not enough simply to bring more light into the cell," says Christiane Becker. Such surface structures can even ultimately reduce the efficiency by impairing the electronic properties of the material.

Rough and smooth

The idea that David Eisenhauer worked out as part of his doctorate in Becker's team sounds quite simple, but it requires a completely new approach: to produce a structure that behaves "optically rough" and scatters the light, but at the same time provides a "smooth" surface on which the silicon layer (the most important layer of the solar cell) can grow with virtually no defects.

Several steps for the SMART surface

The procedure consists of several steps: first, the researchers imprint an optimised nanostructure onto a still liquid silicon oxide precursor layer that is then cured with UV light and heat. This creates tiny, regularly arranged cylindrical elevations that are ideal for capturing light. However, the absorbing layer of crystalline silicon cannot grow flawlessly on this rough surface, so these structures have an unfavorable effect on the quality of the solar cell. In order to resolve this conflict, a very thin layer of titanium oxide is spin coated on top of the nanostructure in order to produce a relatively smooth surface on which the actual absorber material can be deposited and crystallized.

The coating has the descriptive name "SMART" for smooth anti-reflective three-dimensional texture. It reduces reflections and brings more light into the absorbing layer without impairing its electronic properties. The procedure is now patented.

Christiane Becker heads a Young Investigator Group at the HZB funded by the BMBF under the NanoMatFutur programme. As part of the BerOSE Joint Lab, she works closely with the Zuse Institute to use computer simulations for understanding the effects of nanostructuring on material properties.

 

Published in Scientific Reports (2017): Smooth anti-reflective three-dimensional textures for liquid phase crystallized silicon thin-film solar cells on glass; David Eisenhauer, Grit Köppel, Klaus Jäger, Duote Chen, Oleksandra Shargaieva, Paul Sonntag, Daniel Amkreutz, Bernd Rech & Christiane Becker 

doi: 10.1038/s41598-017-02874-y

 

arö

You might also be interested in

  • HZB receives funding to make innovations usable more quickly
    News
    23.03.2023
    HZB receives funding to make innovations usable more quickly
    The Helmholtz Association has selected three new innovation platforms that will now be funded. HZB is involved in two of them: The Innovation Platform on Accelerator Technologies HI-ACTS is intended to open up modern accelerators for a wide range of applications, while the Innovation Platform Solar TAP is intended to bring new ideas from the laboratories of photovoltaics research more quickly into an application. In total, HZB will receive 4.2 million euros in grants from the Pact for Research and Innovation over the next three years.


  • Urban Innovation Forum 2023
    News
    22.03.2023
    Urban Innovation Forum 2023
    Urban Innovation Forum UIF 2023 brings together a diverse group of urban innovators, thought leaders, entrepreneurs and advocates to explore how breakthroughs in urban tech can accelerate the sustainable transformation of urban spaces. 

    Join the Session on 30 March 2023

    02:45 - 03:30 pm GREEN BUILDINGS & PROPTECH

    How do we decarbonize the energy system of the building stock, infrastructure, and cities? How do we create Business showcases in a decentralized and sustainable energy generation. How do we reach the energy efficiency of residential and commercial buildings?

    Speakers:

    // Samira Aden, Helmholtz-Zentrum Berlin // Karolina Attspodina, WeDoSolar // Fabian Reetz, Everyone Energy //Gerrit Peters, Below2 // Moderation: Totinia Hörner

    The UIF 2023 is a partner event of the Berlin Energy Transition Dialogue (BETD) from the Federal Goverment.

  • Green hydrogen: How photoelectrochemical water splitting may become competitive
    Science Highlight
    20.03.2023
    Green hydrogen: How photoelectrochemical water splitting may become competitive
    Sunlight can be used to produce green hydrogen directly from water in photoelectrochemical (PEC) cells. So far, systems based on this "direct approach" have not been energetically competitive. However, the balance changes as soon as some of the hydrogen in such PEC cells is used in-situ for a catalytic hydrogenation reaction, resulting in the co-production of chemicals used in the chemical and pharmaceutical industries. The energy payback time of photoelectrochemical "green" hydrogen production can be reduced dramatically, the study shows.