Combinatorial Fabrication and Studies of Small Molecular Organic Light-Emitting Devices

摘要

Various combinatorial matrix arrays of UV-violet, white, and blue-to-red organic light-emitting devices (OLEDs), fabricated using a sliding shutter technique, are described. In the UV-violet devices, which contain a UV-violet emitting layer of 4,4'-bis(9-carbazolyl) biphenyl (CBP), the optimal radiance R and external quantum efficiency η_(ext) were determined with respect to the thicknesses of the hole transporting layers. In the blue-to-red devices, which contained a blue-emitting layer of 4,4'-bis(2,2'-diphenyl-vinyl) -1,1'-biphenyl (DPVBi) and a red-emitting 5 wt.% dye-doped guest-host layer, the color of the devices evolved continuously from blue to red as the thickness of the doped layer increased from 0 to 35 A. The (nominal) 2 A-thick doped layer device exhibited the highest brightness L ～ 120 Cd/m~2 and external quantum efficiency η_(ext) ～4.4 % at a current density of 1 mA/cm~2. In the white OLEDs, which were similar to the blue-to-red devices but with lightly doped emission layer, the highest brightness L_(max) was over 74,000 Cd/m~2; in all devices L_(max) exceeded 50,000 Cd/m~2. The maximum efficiencies were 11.0 Cd/A, 5.96 lm/W and 4.6% at 5.8 V, 0.6 mA/cm~2, and 68 Cd/m~2 in a 0.25 wt.%, 2 nm-thick doped layer device.