Blue Organic LEDs With Improved Power Efficiency

High-power-efficiency blue fluorescent organic light-emitting devices have been demonstrated by simultaneously doping two hole-conduction layers of 4, 4$^{\prime}$, 4 $^{\prime\prime}$-Tris(N-3-methylphenyl-N-phenyl-amino) triphenylamine (m-MTDATA), and N, N$^{\prime}$-diphenyl-N, N $^{\prime}$-bis(1-naphthyl)-(1, 1 $^{\prime}$-biphenyl)-4, 4$^{\prime}$ -diamine (NPB) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ) as well as doping two ambipolar emission layers with $p$-bis( $p$-N, N-diphenyl-aminostyryl) benzene (DSA-Ph). By doping the two host layers with DSA-Ph to form the double emission layer, the current efficiency is enhanced due to the extended emission zone. We further increase the performance by introducing the doping F4-TCNQ into the hole-injection and transporting layers to reduce the transport barrier at the m-MTDATA:F4TCNQ/NPB and to enhance the hole injection and conduction. The luminance and power efficiencies reach 8.9 cd/A and 4.5 lm/W, respectively.