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HL: Fachverband Halbleiterphysik

HL 13: Poster Session I

HL 13.34: Poster

Montag, 12. März 2018, 17:30–19:30, Poster B

In Situ TEM Studies of Rear Contact Formation of Aluminium with Multi-Crystalline Silicon — •Christoph Flathmann, Tobias Meyer, and Michael Seibt — IV. Physikalisches Institut der Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

For various reasons, the rear contact of a solar cell is a crucial part concerning energy conversion efficiency. The most important requirements are a low resistance ohmic contact and a smooth as well as highly reflective interface, for both minority carriers and photons. In order to create such contacts for multi-crystalline silicon (mc-Si) solar cells, aluminium (Al) is alloyed to the back of the cells. Hence, a heavily Al doped p⁺-region and thus a back-surface field (BSF), which increases cell efficiency, is created. However, rear contacts suffer from flaws due to non-uniform alloying and crystal defects, such as grain boundaries.

To thoroughly investigate the alloying process, cross-section lamellas for transmission electron microscopy (TEM), mimicking the rear of a solar cell, are either prepared employing a focused ion beam or conventionally. Subsequently, the samples are heated and in situ studied by TEM. High resolution and analytical TEM are utilized for analysing structure and chemical composition, respectively. Particular attention is paid to the effect of grain boundaries on the alloying characteristics and the evolution of {113} defects in the silicon during BSF formation.