Regensburg 2013 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 93: Photovoltaics (HL, jointly with CPP, O)

HL 93.10: Vortrag

Freitag, 15. März 2013, 11:45–12:00, H2

Selective laser ablation of Al₂O₃ passivation layers from optically black silicon surfaces — •Martin Otto¹, Katharina Widder¹, Tino Rublack¹, Matthias Zilk², Thomas Käsebier², Gerhard Seifert¹, and Ralf B. Wehrspohn³ — ¹Martin-Luther-University Halle-Wittenberg, Institute of Physics -µ MD Group, Heinrich-Damerow-Strasse 4, 06120 Halle, Germany — ²Friedrich Schiller University Jena, Institute of Applied Physics, Max-Wien-Platz 1, 07743 Jena, Germany — ³Fraunhofer Institute for Mechanics of Materials Halle, Walter-Hülse-Str. 1, 06120 Halle, Germany

Inductive coupled plasma reactive ion etching (ICP-RIE) of silicon enables excellent broad band and wide angle antireflective surface properties. The stochastically emerging needle like nano-structures let the silicon surface appear optically black due to its high absorption coefficient of over 97% integrated from 300 nm to 1175 nm. Concomitant, highly enhanced surface recombination is introduced. The latter, may be effectively suppressed by a well suited passivation layer of Al₂O₃ deposited by thermal ALD. Laser ablation is commonly used in the PV industry to open local contact areas in dielectric passivation stacks. In this work we show the feasibility to ablate alumina thin films from nano-structured black silicon (b-Si) solar cell front surfaces. Micro-structural geometric analysis by focussed ion beam and SEM reveal certain structural changes in the zone of ablation which are believed to be beneficial for contact formation. Simultaneously, neither the deposition of Al₂O₃ layers of varying thickness nor their ablation lead to a very significant degradation of the optical surface properties.