Nanostructured surfaces

Formation of oriented luminescent organic thin films on modified polymer substrate
Karbovnyk I.1, Turko B.2, Sadovyi B.2,3, Klym H.4, Luchechko A.1, Kukhta A.5     
1Department of Electronics and Computer Technologies, Ivan Franko National University of Lviv, 107, Tarnavskogo Str., Lviv, 79000, Ukraine
E-mail: ivan_karbovnyk@yahoo.com
2Department of Physics, Ivan Franko National University of Lviv, 8, Kyryla i Mefodiia Str., Lviv, 79005, Ukraine
3Institute of High Pressure Physics PAS, 29/37, 
Sokolowska Str., Warsaw, 01-142, Poland
4Department of Specialized Computer Systems,
Lviv Polytechnic National University, 12, Bandera Str., Lviv, 79013, Ukraine
5Institute for Nuclear Problems, Belarusian State University, 
11, Babruiskaya Str., Minsk, 220030, Belarus

Orientation of π-conjugated molecules across a large area without defects is attractive for development of manifold electronic devices. It is very important in the formation of interfaces between thin film layers. Luminescent thin films with ordered molecules can be very interesting as active part of organic electroluminescent diodes emitting polarized light. Molecular orientation is known to depend strongly on the substrate surface.
In this work, oriented thin films of blue emitting organic liquid crystalline molecules 4-(n-penthyl)-3-chloro-4///-trifluoromethoxy-[1,1/, 4/, 1//, 4//, 1///- quarterphenyl] were thermally deposited in vacuum on preliminary rubbed  polymer coated optical glass substrates.
The obtained films are stable at ambient conditions. High resolution optical microscope images confirm homogeneous covering of the substrate. Images obtained using Nikon Eclipse LV150 microscope equipped with Lumen 200 Fluorescence Illumination System show pronounced blue luminescence from the film. Polarized photoluminescence measurements indicated that there is a significant difference in blue emission peak intensity for specific directions of polarization vectors of exciting and emitted light.