ECN publication
Title:
Microstructural and mechanical characterisation of Al back contact layers and its application to the thermomechanical multiscale modelling of solar cells
 
Author(s):
Popovich, V.A.; Amstel, T. van; Bennett, I.J.; Janssen, M.; Richardson, I.M.
 
Published by: Publication date:
ECN Solar Energy 16-6-2009
 
ECN report number: Document type:
ECN-M--09-078 Conference Paper
 
Number of pages: Full text:
6 Download PDF  

Presented at: 34th IEEE Photovoltaic Specialists Conference, Philadelphia, USA, 7-12 juni 2009.

Abstract:
The overall demand to reduce the solar energy costs gives a continuous drive to reduce the thickness of silicon wafers. Handling and bowing problems associated with thinner wafers become more and more important, as it can lead to cells cracking and high yield losses. This paper discusses the microstructure and mechanical properties of the aluminium on the rear side of a solar cell. It will be shown that the aluminium back contact has a complex compositelike microstructure, consisting of five main components: 1) back surface field layer 2) eutectic layer 3) spherical (3 - 5 µm) hypereutectic Al-Si particles, surrounded by a thin aluminum oxide layer (200 nm); 4) a bismuth-silicate glass matrix; 5) pores (15 vol.%). The Young’s modulus of the Al-Si particles is estimated by nanoindentation. These results are used as input parameters for an improved thermomechanical multiscale model of a silicon solar cell.


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