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

Abstract

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:MoO(3) (15 v%, 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/m(2) 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.

Electroplex as a New Concept of Universal Host for Improved Efficiency and Lifetime in Red, Yellow, Green, and Blue Phosphorescent Organic Light‐Emitting Diodes

“…Among the many device designs used to achieve high quantum efficiency (QE) and long operational stability, a mixed host device that adopts a hole transport type host and an electron transport type host would be a strong candidate to avoid the TTA and TPA degradation mechanisms 5. Two types of mixed hosts, i.e., exciplex free mixed hosts and exciplex mixed hosts, are known to provide high efficiency and long lifetimes in red, green, and blue PhOLEDs 6.…”

Spectral characterizations and photophysical properties of one-step synthesized blue fluorescent 4′-aryl substituted 2,2′:6′,2′′-terpyridine for OLEDs application

“…However, the blue emission OLED is still dimmer than that of green and red emitting OLEDs, because the deep-blue emitting materials have its intrinsic wide band gap, so it is slightly difficult task to prepare materials with blue-emitting regime [22]. Y. Li et al were studied phosphorescent-host mixed blue emission in order to improve the efficiency and life time of blue-emitting device [23]. Nevertheless, designs of blue phosphorescent materials are still under investigations.…”

66‐1: Invited Paper: Hole‐Transport Materials — Key Enablers for Future OLED Display Evolution

“…1) This development was enabled by high performing materials as well as more refined OLED stack layouts to allow defined charge control with low resistance. 2) The fundamental role of hole transport materials is to control hole supply in these OLED devices. Preferred hole transport materials show high hole mobilities (> 2 x 10 -4 cm 2 V -1 ) and well aligned HOMO energy levels to the adjacent emissive layer.…”