Improved performance of white polymer light emitting diodes

White polymer light-emitting diodes (WPLEDs) with bilayer structure were fabricated by spin coating method using polymers of different solubilities. The device structure used here is ITO/PEDOT(50 nm)/PVK: PFO-BT: PFO-DBT(40 nm)/PFO(40 nm)/Ba(4 nm)/Al(120 nm) at the weight ratio of 100:4:3 (PVK: PFO-BT: PFO-DBT). White fluorescent light emission with CIE coordinates of (0.33, 0.34) is achieved, and the maximal luminance efficiency of 2.4 cd/A and the maximal luminance of 3215 cd/m(2) are obtained. By attaching a layer of water-soluble electronic transporting material of PFN to the cathode, the maximal luminance efficiencies increase up to 5.28 cd/A with CIE coordinates kept at (0.34, 0.36), and the device stability is also improved.