EDMR of MEH-PPV LEDs

In this work, electrically detected magnetic resonance (EDMR) at X-band is used to study the electronic properties of poly(2-metoxy-5-(2'-etil-hexiloxy)-1,4-phenylene vinylene) (MEH-PPV) light-emitting diodes (LEDs). The EDMR signal from MEH-PPV LEDs is found to be composed of two lines, a Lorentzian with peak-to-peak linewidth of 5 G, and a Gaussian with peak-to-peak linewidth of 24 G. The g-factor of both the components is about 2.002. The EDMR signal amplitude is typically 10(-5), and only observed at forward bias, for V > 10 V. The signal is a quenching, and is assigned to the spin-dependent fusion of two like-charged polarons to spinless bipolarons. The Lorentzian component is attributed to positive polarons fusion, and the Gaussian to negative polarons. The EDMR signal is found to depend on the process of carrier injection, polaron mobility, temperature and indirectly on bipolarons. (C) 2001 Elsevier Science B.V. All rights reserved.