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Proceedings Paper

Fs-laser micromachining for µ-TLM resistivity test structures in photovoltaic TCO multilayers
Author(s): Stephan Krause; Kai Kaufmann; Kevin Lancaster; Volker Naumann; Stephan Großer; Christian Hagendorf
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Paper Abstract

In this work we developed a new approach for resistivity measurements based on fs laser micro machining of μ-TLM test structures. This method is applied to highly resistive interfacial and conductive bulk multilayer systems in photovoltaic TCO thin film devices. Resistivity data has been acquired by a new TLM based method at μm-dimensions (μ-TLM, patent pending, DE 102014211352.0). For this approach, isolating trenches are prepared in the µm range with reasonable effort using fs laser processing. The application of ultrashort pulses with a laser wavelength in the IR range (λ = 1.03 μm) allows selective removal of the top SnO2 layer of the TCO multilayer stack by a reduced thermal influence on the layers beneath and in the adjacent region of the laser trenches. Small effective optical penetration and ablation depth was achieved by an ultrafast thermal ablation mechanism via free carrier absorption at the interface of the SnO2/ITO layers. Therefore the risk of laser induced modification of the electric layer properties is negligible. The μ-TLM test structure results in highly accurate and reproducible resistivity data. Applied to SnO2/ITO/glass double layer stacks, the obtained resistivity values for the SnO2 interfacial layer (ρTO = 40.5 kΩμm) and for the indium tin oxide thin film (ρITO = 1.3 Ωμm) agree with reference data from four-point-probing and from literature.

Paper Details

Date Published: 29 April 2016
PDF: 8 pages
Proc. SPIE 9898, Photonics for Solar Energy Systems VI, 98980R (29 April 2016); doi: 10.1117/12.2234613
Show Author Affiliations
Stephan Krause, Fraunhofer-Ctr. für Silizium-Photovoltaik (Germany)
Kai Kaufmann, Hochschule Anhalt Univ. of Applied Sciences (Germany)
Kevin Lancaster, Fraunhofer-Ctr. für Silizium-Photovoltaik (Germany)
Volker Naumann, Fraunhofer-Ctr. für Silizium-Photovoltaik (Germany)
Stephan Großer, Fraunhofer-Ctr. für Silizium-Photovoltaik (Germany)
Christian Hagendorf, Fraunhofer-Ctr. für Silizium-Photovoltaik (Germany)

Published in SPIE Proceedings Vol. 9898:
Photonics for Solar Energy Systems VI
Ralf B. Wehrspohn; Andreas Gombert, Editor(s)

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