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Proceedings Paper

Mid-infrared resonant ablation for selective patterning of thin organic films
Author(s): Sanjeev Naithani; Charles Duterte; Marieta Levichkova; Arnaud Grisard; David Schaubroeck; Eric Lallier; Yves Hernandez; Karsten Walzer; Geert Van Steenberge
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Paper Abstract

The fast growing market of organic electronics, including organic photovoltaics (OPV), stimulates the development of versatile technologies for structuring thin-film materials. Ultraviolet lasers have proven their full potential for patterning single organic layers, but in a multilayer organic device the obtained layer selectivity is limited as all organic layers show high UV absorption. In this paper, we introduce mid-infrared (IR) resonant ablation as an alternative approach, in which a short pulse mid-infrared laser can be wavelength tuned to one of the molecular vibrational transitions of the organic material to be ablated. As a result, the technique is selective in respect of processing a diversity of organics, which usually have different infrared absorption bands. Mid-IR resonant ablation is demonstrated for a variety of organic thin films, employing both nanosecond (15 ns) and picosecond (250 ps) laser pulses tunable between 3 and 4 microns. The nanosecond experimental set-up is based on a commercial laser at 1064 nm pumping a singly resonant Optical Parametric Oscillator (OPO) built around a Periodically-Poled Lithium Niobate (PPLN) crystal with several Quasi-Phase Matching (QPM) periods, delivering more than 0.3 W of mid-IR power, corresponding to 15 μJ pulses. The picosecond laser set-up is based on Optical Parametric Amplification (OPA) in a similar crystal, allowing for a comparison between both pulse length regimes. The wavelength of the mid-infrared laser can be tuned to one of the molecular vibrational transitions of the organic material to be ablated. For that reason, the IR absorption spectra of the organic materials used in a typical OPV device were characterized in the wavelength region that can be reached by the laser setups. Focus was on OPV substrate materials, transparent conductive materials, hole transport materials, and absorber materials. The process has been successfully demonstrated for selective thin film patterning, and the influence of the various laser parameters is discussed.

Paper Details

Date Published: 1 May 2014
PDF: 12 pages
Proc. SPIE 9135, Laser Sources and Applications II, 91350K (1 May 2014); doi: 10.1117/12.2052763
Show Author Affiliations
Sanjeev Naithani, IMEC (Belgium)
Univ. Gent (Belgium)
Charles Duterte, Multitel A.S.B.L. (Belgium)
Marieta Levichkova, Heliatek GmbH (Germany)
Arnaud Grisard, Thales Research & Technology (France)
David Schaubroeck, IMEC (Belgium)
Univ. Gent (Belgium)
Eric Lallier, Thales Research & Technology (France)
Yves Hernandez, Multitel A.S.B.L. (Belgium)
Karsten Walzer, Heliatek GmbH (Germany)
Geert Van Steenberge, IMEC (Belgium)
Univ. Gent (Belgium)

Published in SPIE Proceedings Vol. 9135:
Laser Sources and Applications II
Jacob I. Mackenzie; Helena JelÍnková; Takunori Taira; Marwan Abdou Ahmed, Editor(s)

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