Abstract
The dissertation aims to develop all-solution-processed small molecule organic light-emitting diodes. The emissive layer contains a bipolar 4,4'-bis(carbazol-9-yl)biphenyl (CBP) host or 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (26DCzPPy) and iridium(III) bis(4-(4-t-butylphenyl)thieno[3,2-c]pyridinato-N,C2')acetylacetonate (PO-01-TB) emitter with optimal weight ratio of 94:6 dissolved in chloroform. Uniform dispersion of iridium complex in polymer host poly(vinylcarbazole) is achieved. Tri-layer structure with hole transporting layer, host-guest emissive layer, and hole blocking layer is made by blade-only technique. Current efficiency of 41 cd/A, power efficiency of 21 lm/W, and luminance of 30,000 cd/m2 are achieved for orange-emitting device. The low work function cathode of blade-coated organic light-emitting diode is transferred from a soft polydimethylsiloxane (PDMS) mold by lamination without vacuum. The cathode is a bilayer of polyethylene glycol (PEG) (< 10 nm) and Al (100 nm) . A sacrificial layer of polystyrene with low Mw 1,500 and melting point of 120 ℃ is inserted between the cathode and PDMS for the subsequent mold removal at 150 ℃ by melting polystyrene. Current efficiency of 3.3 cd/A (1.1 %) and luminance of 2500 cd/m2 are achieved for green polyfluorene fluorescent emitter. 25 cd/A (8.2 %) and 3200 cd/m2 are achieved for green phosphorescent tris[2-(p-tolyl)pyridine]iridium(III) (Ir(mppy)3) emitter in polymer blend host. The efficiency is about 70 percent of the devices with thermally evaporated cathode.