A white emitting organic diode with a doped blocking layer

A novel white emitting organic diode has been simply realized by inserting a doped hole-blocking layer between the hole transporting layer (RTL) and t he electron transporting layer (ETL). The structure of this device is ITO/C uPc/NPB/blocking layer:rubrene/Alq/MgAg. Copper phthalocyanine(CuPc) was us ed as a buffer layer, N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4 '-diamine (NPB) as the HTL, and trimer of N-arylbenzimidazoles (TPBi) as th e blocking layers, in which rubrene is doped. Tris(8-quinolinolato)aluminum complex(Alq) as ETL. Indium tin oxide and MgAg were the anode and cathode, respectively. The emission spectrum of this device covers a wide range of visible region and can be sensitively adjusted by the concentration of rubr ene. The white emission with the CIE (Commission International de I' Eclair age) color coordinates x = 0.31, y = 0.32, a maximum luminance of 8635 cd/m (2), and the luminous efficiency 1.39 lm/W at the luminance of 100 cd/m(2) were obtained in the device with 1.5% rubrene concentration in TPBi.