Lh. Slooff et al., Near-infrared electroluminescence of polymer light-emitting diodes doped with a lissamine-sensitized Nd3+ complex, APPL PHYS L, 78(15), 2001, pp. 2122-2124
We report 890 nm luminescence from a neodymium-doped polymer light-emitting
diode. The active layer is a blend of poly(dioctylfluorene-co-benzothiadia
zole), F8BT, and a lissamine-functionalized terphenyl-based neodymium compl
ex. We detect electroluminescence from both the lissamine (580 nm) and the
Nd3+ complex (890 nm). By comparison with lissamine-free devices we show th
at the lissamine is crucial to infrared emission. The neodymium/lissamine l
uminescence intensity ratio is higher under electrical excitation than unde
r optical excitation, showing that more triplets reach Nd3+ under electrica
l excitation. High turn-on voltages provide a clear indication for charge t
rapping onto the lissamine, and we consider direct triplet formation on the
lissamine to be competing efficiently with respect to slower Dexter-type t
riplet transfer from the F8BT to the lissamine. (C) 2001 American Institute
of Physics.