Stable inverted bottom-emitting organic electroluminescent devices with molecular doping and morphology improvement

Stable inverted bottom-emitting organic light-emitting diodes (IBOLEDs) have been investigated by inserting $n$ -type ${\mathrm{Cs}}_2\mathrm{O}$ dopant between indium-tin oxide bottom cathode and $\mathrm{Al}{\mathrm{q}}_3$ , the combination of which not only improved the morphology of organic layer but enhanced the lifetime of the IBOLED. This $n$ -type doped IBOLED achieved efficiencies of $5.2\mathrm{cd}∕\mathrm{A}$ and $2.0\mathrm{lm}∕\mathrm{W}$ at $20\mathrm{mA}∕{\mathrm{cm}}^2$ . The 20% decay lifetime $\left(t_{80}\right)$ of ${\mathrm{Cs}}_2\mathrm{O}$ doped IBOLED is $270\mathrm{h}$ which is about 1.7 times more stable than that of the conventional OLED $\left(160\mathrm{h}\right)$ and 2.5 times of Li doped IBOLED $\left(104\mathrm{h}\right)$ .