White Polarized Electroluminescence Devices by Dye Deposition on Oriented Polyfluorene Films

Abstract

White polarized electroluminescent (EL) devices were produced by deposition of α-sexithiophene (6T), which is an orange-emitting dye, on blue-emitting oriented poly(9,9-dioctylfluorene) (PFO) polymer films produced by the friction transfer method. The results showed that the color of the emitted light changed from blue to white with increasing 6T film thickness. In addition, good polarization of the light was observed, suggesting that 6T molecules are oriented parallel to the direction of the underlying PFO molecules.

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

“…Here, we report the use of oriented ¢-phase PFO films with 6T layers of various thicknesses deposited on top to analyze the effects of the dye on whitening and polarization of the emission of EL devices produced with these structures. We also discuss improvement of the photophysical properties of these devices based on 6T deposited ¢-phase PFO in comparison with previously reported results 11) for those based on 6T deposited N-phase PFO.…”

“…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.…”

“…[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. 11) PFO may show different conformations in the solid state. At room temperature, the energetically more favorable state is a nematic glassy phase with torsional angles between fluorene units (hereafter called N-phase PFO), while the metastable ¢-phase (hereafter called ¢-phase PFO) is composed of more planar fluorene units.…”

Stable pure-blue polymer light-emitting devices based on β-phase poly(9,9-dioctylfluorene) induced by 1,2-dichloroethane

“…olyfluorenes (PFs) are the most widely studied conjugated polymers owing to their wide energy band gap, high photoluminescence (PL) quantum efficiency, high hole mobility, and good solubility, which can be used as active materials in polymer light-emitting devices (PLEDs), photovoltaics, and lasers. [1][2][3] However, one drawback that has limited the application of PFs in blue PLEDs is their poor spectral stability. An additional low-energy emission band between 500 and 600 nm may appear and become pronounced upon thermal annealing or passage of current.…”

Linearly polarized emission from self-assembled microstructures of mesogenic polythiophenes

“…9,10 White and full color electroluminescence with polarization is rapidly gaining research interest since it can result in highly efficient and wide view displays. 7,[11][12][13] As a common criterion, the uniaxial alignment of molecules is used for linearly polarized emission from organic luminogens. 7 Many methods used for polarized electroluminescence address the problem through the preservation of uniaxial alignment.…”