Improving working lifetime and efficiency of phosphor doped organic light-emitting diodes

Long working lifetime and high efficient phosphorescent organic light-emitting diode (PHOLED) in which mixed host composed of wide-band-gap based 4, 7-diphenyl-1, 10-phenanthroline (Bphen) and (4,4'-bis(carbazol-9-yl)- biphenyl) (CBP) was demonstrated. The PHOLED with structure of ITO / MoO ₃ / CBP:MoO₃ (15v%, 30 nm) / CBP(10 nm) / ([50v%:50v% CBP:Bphen]: 6v% Ir(ppy)3)(30 nm) / Bphen (40 nm) / LiF (1 nm) / Al offers a peak power efficiency of 41.6 lm/W (a peak current efficiency of 39.8 cd/A)) at a low driving voltage of 3 V which increases by 55% and 27% compared to that of corresponding single-host (SH) and double emitting layer (DML) devices, respectively. Especially very long work lifetime (3530 hs) at an initial luminance of 500 cd/m2 of the mixed hosted device is exhibited, rising by about 4.1 and 2.46 times relative to that of corresponding SH and DML devices. High efficiency and longer working lifetime was attributed to the absence of heterojunction and balanced charge carrier transport characteristics in the mixed host based OLED structure. The more detail mechanism was also presented.