Enhanced efficiency and brightness in organic light- emitting devices with MoO3 as hole-injection layer

Abstract:

The organic light-emitting devices (OLEDs) using 4,4’,4’’-tris{N-(3-methylphenyl)-N-phenylamin}triphenylamine (m-MTDATA) and MoO3 or 1,3,5-triazo-2,4,6-triphosphorine-2,2,4,4,6,6-tetrachloride (TAPC) and MoO3 as the hole-injection layer (HIL) were fabricated. MoO3 can be expected to be a good injection layer material and thus enhance the emission performance of OLED. The highest occupied molecular (HOMO) of MoO3 is between those of m-MTDATA or TAPC and N,N’-bis-(1-naphthyl)-N,N’-diphenyl-1,1’-biphenyl-4,4’-diamine (NPB), which reduces the hole-injection barrier and improves the luminance of the OLEDs. The current efficiency is improved compared with that of the device without the MoO3 layer. The highest luminous efficiency of the device with 2-nm-thick MoO3 as HIL is achieved as 5.27 cd/A at 10 V, which is nearly 1.2 times larger than that of the device without it. Moreover, the highest current efficiency and power efficiency of the device with the structure indium-tin oxide (ITO)/TAPC (40 nm)/MoO3 (2 nm)/TcTa:Ir(ppy)3 (10%, 10 nm)/ tris-(8-hydroxyquinoline) aluminium (Alq) (60 nm)/LiF (1 nm)/Al are achieved as 37.15 cd/A and 41.23 lm/W at 3.2 V and 2.8 V, respectively.