Utilizing Hole-Type Sensitizer Tris (Phenylpyrazole) Iridium (Ir(ppz)3) to Realize Efficient Red Organic Light-Emitting Devices

We design and fabricate highly efficient red organic electroluminescent (EL) devices by utilizing iridium(III) bis(2-phenylquinoly-N,C2’)dipiva1oy1methane $(\mathrm{P}\mathrm{Q}_{2}\mathrm{I}\mathrm{r}(\mathrm{d}\mathrm{p}\mathrm{m}))$ and tris(phenylpyrazole) iridium $(\mathrm{I}\mathrm{r}(\mathrm{p}\mathrm{p}\mathrm{z})_{3})$ as emitter and hole-type sensitizer, respectively. Experimental results demonstrated that sensitizer molecules within hole-dominant EML function as hole trappers, thus delaying the transport of holes. Finally, the optimized co-doped device obtained the external quantum efficiency, maximum brightness and current efficiency up to 18.9%, 87370 cd/m2 and 51.09 cd/A, respectively.