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 (HTL) and the electron transporting layer (ETL). The structure of this device is ITO/CuPc/NPB/blocking layer : rubrene/Alq/MgAg. Copper phthalocyanine(CuPc) was used as a buffer layer, N,N’-bis-(I-naphthy1)-N,N’-diphenyl-1,1’-bipheny1-4,4’-diamine (NPB) as the HTL, and trimer of N-arylbenzimidazoles (TPBi) as the blocking layers, in which rubrene is doped. Tris(8-quinolino1ato)aluminum complex(A1q) 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 rubrene. The white emission with the CIE (Commission International de 1’ Eclairage) color coordinates x = 0.31, y = 0.32, a maximum luminance of 8635cd/m², and the luminous efficiency 1.391m/W at the luminance of 100cd/m² were obtained in the device with 1.5% rubrene concentration in TPBi.