Single-layer organic light-emitting diodes using naphthyl diamine

N,N-'-diphenyl-N,N-'-bis(1-naphthyl)(1,1(')-biphenyl)-4,4(')diamine (NPB), a common hole transporter, was employed to fabricate single-layer organic light-emitting diodes (OLEDs). With a quasi-Ohmic anode, NPB device exhibited a bulk-limited hole current in the low-voltage region. Electron injection and light emission were clearly observed for applied voltages exceeding 4 V. In order to confine the recombination zone, intentional doping was applied to the single-layer device. After doping with perylene, the luminance and current efficiency of NPB device increased dramatically. It is expected that more efficient single-layer OLEDs can be achieved by using the doping strategy. (c) 2007 American Institute of Physics.