Bias-tuned reduction of self-absorption in polymer blend electroluminescence

We present a concentration- and bias-dependent electroluminescence study on MEH-PPV aggregation in a binary polymer blend with the blue-emitting Me-LP PP as host In low-concentration blends the spectral features of MEH-PPV pea k at 560 nm, identical to its photoluminescence spectrum in dilute solution , and therefore suggesting effective hindering of aggregation-induced self- absorption. At higher concentrations the electroluminescence spectra an dom inated by MEH-PPV peaking at 600 nm and a dramatic shift of spectral weight to the 560 nm peak is observed with increasing bias. We attribute this nov el effect to a reduction of self-absorption caused by either photo- or char ge-induced bleaching. (C) 2000 Elsevier Science B.V. All rights reserved.