Oriented Polyfluorene Films Dye-Doped for Whitening of Polarized Electroluminescent Devices

Abstract

Whitening of the emission of electroluminescent (EL) devices was performed by doping -sexithiophene (6T), which is an orange emitting dye, into blue emitting oriented poly(9,9-dioctylfluorene) (PFO) polymer films. These oriented PFO films were produced by means of the friction transfer method and the doping of 6T was performed by means of the vapor transportation method which is a solvent-free process. The excellent orientation of PFO films and of the doped 6T led to very good polarization of the light emitted by these EL devices.

White Polarized Electroluminescence Devices by Dye Deposition on Oriented Polyfluorene Films

“…We compared the photoelectric results of these devices with those of devices we produced by doping 6T into the oriented PFO. 9) The turn-on voltage (i.e., the bias required to give a luminance of 1.0 cd/m 2 ) is about 4 V for both the 6T deposited and 6T doped devices. For devices produced with 6T deposition, maximum luminance was 380 cd/m 2 , efficiency 0.1 cd/A, current density 390 mA/cm 2 at 9 V with CIE chromaticity diagram coordinates ð0:30; 0:32Þ.…”

“…We have been exploring these characteristics, in combination with appropriate doping techniques, for the purpose of changing the color of the device in a controlled manner to allow the production of devices that emit white light. 8,9) For doping, we have been applying the vapor transportation method, 9,10) which is especially suitable for oriented films because it allows doping after film production without the loss of molecular orientation. While we were able to apply this method for the whitening of -sexithiophene (6T)-doped oriented PFO films that emit polarized light, 9) intrinsically this process does not allow good control of the amount of dye doped into the matrix film.…”

“…8,9) For doping, we have been applying the vapor transportation method, 9,10) which is especially suitable for oriented films because it allows doping after film production without the loss of molecular orientation. While we were able to apply this method for the whitening of -sexithiophene (6T)-doped oriented PFO films that emit polarized light, 9) intrinsically this process does not allow good control of the amount of dye doped into the matrix film. The present study was performed to gain further insight into the mechanism underlying the emission of white polarized light from these devices by analyzing the effects of the amount and of the morphology of the dye at the interface/emitting region.…”

Polarized electroluminescent devices based on ultrathin α-sexithiophene on oriented β-phase polyfluorene films

“…For the orientation of PFO films, the friction transfer method was employed. [9][10][11][12] For doping 6T into these oriented PFO films, one of the techniques employed was the self-developed vapor transportation method. This led to whitening of the polarized light with a significant increase in current efficiency, but this process has intrinsically poor control of the doping amount.…”

“…This led to whitening of the polarized light with a significant increase in current efficiency, but this process has intrinsically poor control of the doping amount. 9,13) Another technique employed was the deposition of 6T directly onto these oriented PFO films, considering that the rod-shaped 6T molecules align parallel to an oriented polymer substrate. [14][15][16][17][18] Excellent control of the emission color was possible by varying 6T thickness, and devices with white polarized emission were produced, but these devices showed very low current efficiency.…”