General method to solution-process multilayer polymer light-emitting diodes

Abstract

An intermediate liquid buffer layer is introduced to overcome the dissolution problem of solution-processed multilayer conjugated polymer light-emitting diodes. This method can be applied to arbitrary combinations of polymers with no restriction on solvents. As an example, a hole-blocking layer is successfully spin coated on the common p -type emissive polymer layers. One green- and two blue-emitting polymers are chosen as the emissive layers. The electron-hole balance and efficiency are significantly improved by the addition of hole-blocking layer. The electroluminescence efficiency can be increased up to nine times, while the luminance up to seven times. In particular, 1.5 cdA is obtained for deep blue emission from poly(9,9-dioctyl-fluorene) with 1,3,5-tris (N -phenylbenzimidazol-2-yl)benzene spin coated as the hole-blocking material. © 2006 American Institute of Physics.