Optical study of a polymeric LED with a nano-sized electrode realized by amodified SNOM setup

Semiconductive polythiophene derivate polymers show electroluminescence (EL ) properties if excited under opportune conditions and can be used as activ e element in novel efficient light-emitting diodes (LEDs) or in photovoltai c applications as detectors or solar cells. These intriguing and innovative materials are so far studied in bulk condition, under the excitation of tw o macroscopic electrodes, averaging the optical phenomena over a large regi on. To realize a better understanding of the spatial distribution of the EL on the films and its optical properties, we modified a scanning near-field optical microscope (SNOM) setup in order to measure the EL signal of poly- 3-(2-(5-chlorobenzotriazolo)ethyl)thiophene. The film were deposited over a macroscopic electrode substrate (a transparent indium tin oxide (ITO) trea ted glass), while a sharp aluminum coated glass probe worked as a nano-size d Al electrode, realizing an Al/ polymer/ITO light emitting device in a hig hly confined region. We describe in detail the methodology we used for the novel EL measurements and we will show the first resulting high-resolution EL emission mapping, as well as other spectroscopic and morphological chara cterization of the film used. (C) 2001 Published by Elsevier Science B.V.