Defect states investigation in poly(2-methoxy,5-(2 ' ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV)

Abstract

in this study, application of the charge based Deep Level Transient Spectroscopy (Q-DLTS) has been extended to poly(2-methoxy,5-(2ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV) single layer diodes, whose cathode consisted of aluminium and anode of indium tin oxide (ITO). The results reveal a broad Q-DLTS spectrum, with at least two maxima, consistent with a complex distribution of trap states. Only the Q-DLTS maximum with the shortest relaxation time could be fully resolved over the temperature range used here (100-300 K), yielding activation energies and capture cross sections in the ranges 0.3-0.4 eV and 10(-20) 10(-18) cm(2), respectively. It will be shown that this energy level is likely related to a majority-carrier (hole) trap, consistent with a Poole-Frenkel injection mechanism and p-type doping of the MEH-PPV film. The origin of the second (non-resolved) Q-DLTS peak will also be discussed. (c) 2005 Elsevier B.V. All rights reserved.