Bright-yellow molecular organic light-emitting diodes based on two novel silole derivatives

Abstract

High-efficient molecular organic light-emitting diodes using two novel silole derivatives as emitter is reported in the paper. Multilayer organic light-emitting diodes with a structure of indium tin oxide(ITO)/N, N'-bis- (1-naphthyl)-N,N'-biphenyl-1,1'-biphenyl-4,4'-diamine (NPB)/2,5-bis(9,9-dimethyl-9H-fluorene-2-yl)-1,1,3,4-tera-phenylsilole (DMFPSi)/tri-(8-hydroxyquinoline)- aluminum (Alq₃)/Mg:Ag and ITO/NPB/2,5-bis(thiophene-2-yl)--1,1,3,4-tetraphenyl-1H-silole (BTTPSi)/Alq₃/Mg:Ag have been fabricated, where Alq₃ was used as an electron transport layer. These two silole derivatives have similar backbone, so EL properties are parallelly characterized. Luminance-voltage and current density-voltage characteristics of both devices were investigated and device performances were discussed. Experimental results demonstrate that the devices consisting of DMFPSi and BTTPSi with high efficiency of yellow light emission, and the maximum luminance of 16,000 cd/m² at bias voltage of 12.5 V and 12,500 cd/m2 at bias voltage of 16.5 V, can be respectively achieved. The maximum luminance efficiencies of 2.35 lm/W at 625 cd/m² for DMFPSi and 0.5 lm/W at 4000 cd/m² for BTTPSi are obtained. The peak of EL spectrum locates at 555 and 580 nm, respectively, which are independent of the variation of bias voltage.