The trap states in poly(9,9-dihexylfluorene-co-N,N-di(9,9-dihexyl-2-fluorenyl)-N-phenylamine) (PF-N-Ph) based light emitting diodes have been investigated by using the thermally stimulated current (TSC) technique in the temperature range of 90-320 K. The studied structure consisted of indium-tin-oxide/polyethylene-dioxythiophene: polystyrene-sulfonate/PF-N-Ph/Al. Four traps centers denoted as A, B, C, and D trap types have been identified with densities in the range of 10(16)-10(17) cm(-3). Study of the dependence of TSC characteristics on the device polarity suggested that the A, C and D type traps are electron traps while the B type traps are hole traps. They can be described by Gaussian distributions centered on mean trap levels. (c) 2008 Elsevier B.V. All rights reserved.