Controlling the optical emission from the polymer MEH-PPV using corrugated thin films

¹ Thin Film Photonics Group, School of Physics, University of Exeter, Exeter, EX4 4QL, UK
² Department of Physics, University of Durham, South Road, Durham, DH1 3LE, UK
³ Polymer Optoelectronics Research Group School of Physics and Astronomy, University of St. Andrews, North Haugh,

Corresponding author: idws@st-andrews.ac.uk

Received: 23 July 2001
Revised: 7 January 2002
Accepted: 8 February 2002
Published online: 15 May 2002

Abstract

We report measurements of photoluminescence from corrugated thin films of a light-emitting polymer. We find that emission into guided modes that would otherwise be trapped in the polymer may Bragg scatter off the corrugation to produce useful, far-field radiation. Analysis of the angle dependence of this far-field emission together with theoretical modeling enables us to establish the nature of the optical modes guided by the structure. We show that the dispersion of the modes supported by corrugated polymer films depends on the depth of modulation of the corrugation and find that if the periodic corrugation is strong enough photonic band gap effects may be induced. We also address the question of whether Bragg-scattering of the guided modes, including surface plasmon polariton modes, may increase the efficiency of the emission. We measure and compare the efficiency with which radiation is produced by planar and corrugated structures, finding the corrugated structures to be up to a factor of 2.6 more efficient. We indicate how our results may be used in the search for ways to improve the efficiency of devices based on light emitting thin films.