Black Silicon surfaces

Light is reflected whenever it passes from one material to another. This also happens when light enters a solar cell. The reflection can be minimized by using anti-reflection coatings such as those often found on glasses/spectacles. On crystalline Silicon, this anti-reflection coating usually consists of a thin layer of SiN3. It is optimized to suppress reflection of red light and does not work as well in the blue, which accounts for the slightly bluish color exhibited by most multicrystalline Si solar cells.

We have developed a new method to structure the surface of Si-based solar cells so that it transmits light with minimal reflection losses over the whole useful spectral range. The technique is based on the local catalytic action of nanometer-sized Au dots when the surface coated with them is exposed to a particular etching solution. The result is a nanostructured surface where the refractive index gradually changes from that of air to that of Si. If this happens on a length scale smaller than the wavelength of light, its reflection is suppressed.

The technique works on all different kinds of Si-based solar cells, including single- and multicrystalline cells as well as cells made from hydrogenated amorphous Silicon. In addition to a reduction of the reflection losses, the nanotextured surfaces lead to the trapping of light, which allows the solar cells to be thinner than those with conventional anti-reflection coatings, resulting in a significant cost reduction.

Selected publications

  • Black nonreflecting silicon surfaces for solar cells
    Applied Physics Letters 88 203107 (2006)
    S. Koynov, M. S. Brandt, M. Stutzmann
  • Black multi-crystalline silicon solar cells
    physica status solidi-rapid research letters 1 R53 (2007)
    S. Koynov, M. S. Brandt, M. Stutzmann
TUM Technische Universität München TUM Technische Universität München Physik Department Elektrotechnik und Informationstechnik TUM Technische Universität München

Recent publications

Interaction of Strain and Nuclear Spins in Silicon: Quadrupolar Effects on Ionized Donors

Phys. Rev. Lett. 115, 057601 (2015)

D. Franke | F. Hrubesch | M. Künzl | H. W. Becker | K. M. Itoh | M. Stutzmann | F. Hoehne | L. Dreher | M. S. Brandt

Online Reference

see also: Nuclear Spins of Ionized Phosphorus Donors in Silicon

Phys. Rev. Lett. 108, 027602 (2012)

L. Dreher | F. Hoehne | M. Stutzmann | M. S. Brandt

Online Reference

Ultrafast electronic read-out of diamond NV centers coupled to graphene

Nature Nanotechnology 10, 135 (2015)

A. Brenneis | L. Gaudreau | M. Seifert | H. Karl | M. S. Brandt | H. Huebl | J. A. Garrido | F. H. L. Koppens | A. Holleitner

Online Reference

Bipolar polaron pair recombination in polymer/fullerene solar cells

Physical Review B 92, 245203 (2015)

A. Kupijai | K. M. Behringer | F. Schäble | N. Galfe | M. Corazza | S. A. Gevorgyan | F. C. Krebs | M. Stutzmann | M. S. Brandt

Online Reference

Broadband electrically detected magnetic resonance using adiabatic pulses

Journal of Magnetic Resonance 254, 62 (2015)

F. Hrubesch | G. Braunbeck | A. Voss | M. Stutzmann | M. S. Brandt

Online Reference

High cooperativity coupling between a phosphorus donor spin ensemble and a superconducting microwave resonator

Appl. Phys. Lett. 107, 142105 (2015)

C. W. Zollitsch | K. Mueller | D. Franke | S. T. B. Goennenwein | M. S. Brandt | R. Gross | H. Huebl

Online Reference

Submillisecond Hyperpolarization of Nuclear Spins in Silicon

Phys. Rev. Lett. 114, 117602 (2015)

F. Hoehne | L. Dreher | D. Franke | M. Stutzmann | L. S. Vlasenko | K. M. Itoh | M. S. Brandt

Online Reference