R. Osterbacka et al., FREQUENCY-RESPONSE OF MOLECULARLY THIN ALTERNATING-CURRENT LIGHT-EMITTING-DIODES, Journal of applied physics, 83(3), 1998, pp. 1748-1752
The frequency response of molecularly thin alternating-current polymer
ic light-emitting diodes has been studied. Langmuir-Blodgett (LB) film
s of poly(3-hexylthiophene) (PHT) were used as the active emitting mat
erial and the device was formed by sandwiching PHT films between LB fi
lms of emeraldine base polyaniline. As a step towards molecular electr
onic devices, we have shown that even two molecular layers of PHT (app
roximate to 6 nm) are sufficient for light emission. The high frequenc
y operation limit of the device has been discussed in terms of a charg
e accumulation process at the polymer-polymer interface. The electrolu
minescence (EL) spectra of different structures have been compared wit
h corresponding photoluminescence spectra. A significant blueshift in
EL has been observed in thinner structures and its origin has been dis
cussed. (C) 1998 American Institute of Physics. [S0021-8979(98)02103-3
].