Interchain excited states in annealed poly [2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylene vinylene] films

Abstract The optical properties of poly [2-methoxy-5-(2'-ethyl-hexyloxy)- p -phenylene vinylene] (MEH-PPV) are studied by examining and analyzing the photoluminescence, ultraviolet–visible absorption and Fourier transform infrared spectra of the polymer films annealed in nitrogen or air atmospheres at different temperatures. The PL peak positions of the annealed spin-coating films are red-shifted markedly because of polymer chain relaxation. The relative intensities of the PL shoulder at 640 nm in the annealed MEH-PPV films are increased with annealing temperature, indicating that thermal annealing facilitates the formation of interchain species. The interchain excited states can be regarded as excimers in the MEH-PPV films since there is an absence of a directly excitable absorption band in ground states.