High performance top-emitting organic light-emitting diodes with copper iodide-doped hole injection layer

Efficient top-emitting organic light-emitting diodes were fabricated using copper iodide (CuI) doped 1,4-bis[N-(1-naphthyl)-N'-phenylamino]-4,4'-diamine (NPB) as a hole injection layer and Ir(PPY)(3) doped CBP as the emitting layer. CuI doped NPB layer functions as an efficient p-doped hole injection layer and significantly improves hole injection from a silver bottom electrode. The top-emitting device shows high current efficiency of 69 cd/A with Lambertian emission pattern. The enhanced hole injection is originated from the formation of the charge transfer complex between Cut and NPB. (C) 2008 Elsevier B.V. All rights reserved.