Optical and electrical characteristics of organic electroluminescent devices with multiple-quantum-well structure

We report for the first time organic multiple-quantum-well-like electroluminescent (EL) devices fabricated by the doping technique. The EL device consists of N,N′-Bis(3-methyphenyl)-N,N′-diphenylbenzidine used as a hole transporter, undoped 8-(quinolinolate)-aluminum(Alq) as a barrier potential or an electron transporter, and Alq doped with 5,6,11,12-tetraphenylnaphthacene as a potential well and a light emitter. The effects of well width and well number on EL device properties are demonstrated. Compared with the characteristics of the heterojunction EL device, the single quantum well EL device shows higher efficiency and luminance, narrower spectrum and higher emission peak energy. Compared with the characteristics of quantum-well EL devices with different well number, our results indicated that the double-quantum-well EL devices have the optimum performance, the efficiency and the luminance of the device achieve 15.7 lm W^-1 and 7500 cd m^-2, respectively.