Today, a variety of polymeric and crystalline materials that show intrinsically
conducting or semiconducting properties are known. Much research was done on
organic electronics in photovoltaic cells, biomedical sensors, and organic thin film
transistors [1]. Currently, various methods to produce intrinsically conducting
polymers are known, and most methods used up to date have substantial limitations
regarding feature size. When it comes to inorganic electronics, photolithographic
processes have very high resolution. The limitations of these processes on organic
electronic materials are primarily due to the incompatibility of the organic materials
with mask-based UV-photolithography and problems in solution processing. The
highest reported resolution achieved with a mask-based photolithographic process
for organic electronics is about 500 nm [2].
On the other hand, optical lithography using two-photon absorption allows for three-
dimensional lithography, achieving structure sizes even below the diffraction limit.
Adding stimulated emission depletion (STED) inspired techniques even improves the
feature sizes down to 40 nm in both lateral and axial directions [3]. However, only
radically polymerizing resists such as (meth)acrylates were used. It would be a great
step forward if STED-inspired lithography could be applied to polymers typically used
in organic electronics.
In this contribution, we demonstrate PEDOT structures produced by two-photon
lithography made by near-infrared femtosecond radiation of a 780 nm laser beam.
We mixed EDOT with UV-sensitive diphenyl iodonium-hexafluorophosphate as a
photostarter for cationic polymerization. In order to start the polymerization process
by visible range radiation, 7-diethylamino-3-thenoylcoumarin (DETC) was used as a
photosensitizer. We demonstrate total polymerization inhibition by 660 nm radiation,
which is well within the transient state absorption spectrum of DETC. Applying a
donut-shaped phase mask to the 660 nm beam, we obtain a PEDOT nanowire of 67
nm lateral width.
[1] Zozoulenko, I., Franco-Gonzalez, J. F., Gueskine, V., Mehandzhiyski, A.,
Modarresi, M., Rolland, N., & Tybrandt, K. (2021). Electronic, optical, morphological,
transport, and electrochemical properties of PEDOT: A theoretical perspective.
Macromolecules, 54(13), 5915-5934.
[2] Shim, H., Jang, S., & Yu, C. (2022). High-resolution patterning of organic
semiconductors toward industrialization of flexible organic electronics. Matter, 5(1),
23-25.
[3] Fischer, J.; Wegener, M., Three-dimensional optical laser lithography beyond the
diffraction limit. Las. Phot. Rev. 2013, 7 (1), 22-44.
| Period | 01 Jun 2023 |
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| Event title | EMRS Spring Meeting |
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| Event type | Conference |
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| Location | FranceShow on map |
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