Flexible Blue Light Emitting Diodes Made from Dye Doped Poly (N-Vinylcarbazole) with Multilayer Structure

Flexible blue light emitting diodes (LEDs) were fabricated by using poly(N-vinylcarbazole) (PVK) doped with high fluorescence dye, 1, 1, 4, 4-tetraphen1-1,3-butadiene (TPB), as a emitter layer, a layer of tris(8-quinolino1ato)aluminum (Ⅲ) (Alq₃) as an electron-transporting layer,and a layer of 2-(4-biphenylyl)-5-(4-tertbutypheny)-1-3,4-oxadiazole (PBD) as hole-blocking layer; a cell structure of flexible substrate/indium-tin-oxide /PVK:TPB/PBD/Alq₃/Al was employed. In this cell structure, carrier injection from the electrodes to the doped PVK layer and concomitant electroluminescence from doped PVK were observed at room temperature with dcbias voltage of 4V. Blue emission peaks at about 465nm. This kind of LED is about 200μm thick and can be curled or bent repeatedly at sharp angles without failure.