The Impact of Illumination on the Photoluminescence and Depth Profile of MEH-PPV/dPS Thin Films

This study focuses on the changes in photoluminescence and film structure due to white light exposure during annealing of conjugated polymer blend thin films. Previous studies in our group have shown that annealing similar polymer blend thin films above the T_g of the polymers in a dark or illuminated environment alters the film structure. These structural changes should influence the photoluminescence (PL) activity observed for the film. The present work aims to investigate the correlation between light exposure, film morphology and photoluminescence for four film compositions, 5, 20, 35, and 50% MEH-PPV. The PL of the films are measured using Raman microscopy, which showed differences in PL activity depending on illumination during annealing at 125 °C. Samples that are exposed to light during annealing exhibited lower PL. Time-of-Flight Secondary Ion Mass Spectroscopy provides the depth profile of the films that enables the correlation of the film’s morphology and depth profile to the observed PL.