Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 45: Photovoltaics: Silicon-based Systems I

HL 45.5: Talk

Wednesday, March 28, 2012, 10:30–10:45, ER 270

Surface recombination in black silicon — •Michael Algasinger, Julie Paye, Svetoslav Koynov, Martin S. Brandt, and Martin Stutzmann — Walter Schottky Institut, Technische Universität München, 85748 Garching, Germany

Nanotextured silicon, also referred to as black silicon (b-Si), shows a reflectivity of around 2-5% in the whole range of Si absorption [1]. The needle-like structure is in a scale of the wavelength of the incident light. According to the model of Stephens and Cody [2] such a surface is an effective medium with a graded optical density, which provides no interface where a reflection could appear. Furthermore, this nanostructure shows light trapping effects, increasing the optical path by a factor of up to 15 [3]. Both effects make b-Si interesting for application in thin film solar cells. The nanostructure is produced by a wet etching process which increases the surface area. This leads to an elevated recombination of photo-induced carriers. In order to benefit from the good optical properties of b-Si in solar cells, the loss in efficiency due to the additional surface recombination needs to be minimized. Effects of different surface treatments on the surface recombination velocity will be compared. First results of diffusion length measurements and electrical detected magnetic resonance (EDMR) will be presented.

[1] S. Koynov, M. S. Brandt, and M. Stutzmann, Appl. Phys. Lett. 88, 203107 (2006).

[2] R. B. Stephens and G. D. Cody, Thin Solid Films 45, 19 (1977).

[3] S. Koynov, M. S. Brandt, and M. Stutzmann, J. Appl. Phys. 110, 043537 (2011).