High efficiency tandem organic light-emitting devices with Al∕WO3∕Au interconnecting layer

An interconnecting layer of Al $\left(2\mathrm{nm}\right)∕\mathrm{W}{\mathrm{O}}_3$ $\left(3\mathrm{nm}\right)∕\mathrm{Au}$ $\left(16\mathrm{nm}\right)$ was studied for application in tandem organic light-emitting devices. It can be seen that the $\mathrm{Al}∕\mathrm{W}{\mathrm{O}}_3∕\mathrm{Au}$ structure plays the role of an excellent interconnecting layer. The introduction of $\mathrm{W}{\mathrm{O}}_3$ in the connection unit significantly improves the device efficiency as compared to the case of $\mathrm{Al}∕\mathrm{Au}$ . Thus, the current efficiency of the two-unit tandem devices is enhanced by two factors with respect to the one-unit devices. The green two-unit tandem device of indium tin oxide/$\mathrm{Mo}{\mathrm{O}}_3∕4,4^{\prime }\text{-}N,N^{\prime }$ -bis[$N$ -(1-naphthyl)-$N$ -phenyl-amino]biphenyl(NPB)/tris(8-hydroxylquinoline) aluminum $\left(\mathrm{Al}{\mathrm{q}}_3\right)$ :10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-$1H,5H,11H$ -[1]benzopyrano[6,7,8-ij]quinolizin-11-one $\left(\mathrm{C}545\mathrm{T}\right)∕\mathrm{Al}{\mathrm{q}}_3∕\mathrm{Li}\mathrm{F}∕\mathrm{Al}∕\mathrm{W}{\mathrm{O}}_3∕\mathrm{Au}∕\mathrm{Mo}{\mathrm{O}}_3∕\mathrm{NPB}∕\mathrm{Al}{\mathrm{q}}_3:\mathrm{C}545\mathrm{T}∕\mathrm{Al}{\mathrm{q}}_3∕\mathrm{Li}\mathrm{F}∕\mathrm{Al}$ showed a maximum current efficiency of $33.9\mathrm{cd}∕\mathrm{A}$ and a power efficiency of $12.0\mathrm{lm}∕\mathrm{W}$ .