Fabrication of Molecular Micro-NanoStructures by Surface-Tension-Driven Technique
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1002-N06-04
Fabrication of Molecular Micro-NanoStructures by Surface-Tension-Driven Technique Ilenia Viola1, Fabio Della Sala1, Manuel Piacenza1, Laura Favaretto2, Massimo Gazzano2, Giovanna Barbarella2, Roberto Cingolani1, and Giuseppe Gigli1 1 National Nanotechnology Laboratory (NNL) of INFM-CNR, Lecce, 73100, Italy 2 ISOF of CNR, Bologna, 40129, Italy .
We present the fabrication of a pixels structure by a well-defined pattern replication of a micrometer template driven by a surface free-energy lithographic technique, realized by molecular aggregation in dewetting conditions and by confining the liquid solution with geometric boundaries. The organization in the solid-state of the selected thiophene-based molecular materials allows to realize a bicoloured, green and red-emitting pixels structure, by exploiting the molecular structural arrangement, induced during a dewetting process, and the great conformational flexibility of DTT7Me.
In the last years, advantages in the use of organic semiconductors have been attributed to low temperature and solution processing, fabrication over large areas and also on flexible plastic substrates. However, one of the main challenges that remain unsolved in organic technologies is the control of the solid-state supra-molecular arrangement and there is still a gap of information on how molecular ordering and morphology are in connection with opto-electronic properties [1ñ3]. Solid-state supra-molecular organization of conjugated molecular systems, and in particular of π-conjugated oligomers, plays an important role in the field of organic electronics and photonics [46], such as light-emitting diodes (LEDs) [7], field-effect transistors (FETs) [8], photovoltaic cells [9]. Organic materials allow, in fact, a fine tuning of desirable functional properties, strongly dependent, especially in the solid-state, both by the molecular structure and by the supra-molecular organization. Besides, lighting technologies based on organic compounds have required, up to now, the control both of the intrinsic molecular light emission and of the suitable colour combinations. Spin-coating, thermal evaporation or co-evaporation have been usually carried out as a costeffective technique for the deposition of organic layer. As an example, a recent work of Mazzeo et al., in our group, has demonstrated the white-light emission from organic LEDs (OLEDs), based on oligothiophene spin-coated layer [10]. The white emission is realized by the superposition of a broad blue-green-light emission, originating from the single molecule, and a narrow red-shifted emission, resulting from the formation of cross-like dimers in the solid-state. On the other hand, the realization of integrated devices with micro and submicrometer sizes needs the development of advanced litographies suitable for soft materials, that represents the main obstacle to the exploiting of such materials. Different strategies for patterning molecular materials in a controlled way are currently under
investigation, ranging from top-down (soft em
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