Temperature-Dependent Performance of Organic Light-Emitting Devices based on Solution-Processed N,N-Bis-(1-Naphthyl)-N,N-Diphenyl-1,1-Bip henyl-4,4-Diamine Hole Transport Layers

A series of green organic light-emitting diodes (OLEDs) that consisted of a tris-(8-hydroxyquinoline)aluminum emitting layer and an N,N '-bis-(1-naphthyl)-N,N '-diphenyl-1,1 '-biphenyl-4,4 '-diamine (NPB) hole transport layer were fabricated and characterized. The NPB layers were formed using a solution process and heated at different temperatures. All the fabricated OLEDs showed similar electroluminescence spectra: however, different heat treatment temperatures resulted in efficiency variations. The peak luminous efficiency revealed a significant increase by similar to 70% when the temperature was increased from 80 degrees C to 100 degrees C and a dramatic decrease by similar to 57% after a further increase in temperature to 110 degrees C. As a result, the best performance was observed from the device with a treatment temperature of 100 degrees C; the maximum luminance and luminous efficiency were 7600 cd/m(2) and 2.75 cd/A, respectively. [GRAPHICS]