Yuan-Li Liao

Triphenylsilyl- and Trityl-Substituted Carbazole-Based Host Materials for Blue Electrophosphorescence

Carbazole-based materials adopting the nonconjugated substitution of triphenylsilyl (-SiPh(3)) and trityl (-CPh(3)) side groups are studied as high-triplet-energy, morphologically, and electrochemically stable host materials with tunable carrier-transport properties for organic blue electrophosphorescence. The developed host materials 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi), 9-(4-tert-butylphenyl)-3,6-ditrityl-9H-carbazole (CzC), and 9-(4-tert-butylphenyl)-3-(triphenylsilyl)-6-trityl-9H-carbazole (CzCSi) all show high triplet energies of 2.97-3.02 eV, along with high glass transition temperatures of 131-163 degrees C and superior electrochemical stability. Nevertheless, the carrier-transport properties show rather significant dependence on different substitutions. Although three different host materials give similar peak electroluminescence efficiencies at low driving currents, the CzSi host, which has more suitable carrier-transport properties, renders broadened distributions of the triplet excitons in phosphorescent devices, reducing the quenching associated with triplet-triplet annihilation and giving larger resistance against efficiency roll-off at higher brightnesses.

Synthesis and properties of pyrimidine-containing linear molecules

Abstract Palladium-catalyzed Stille and Sonogashira coupling reactions were sequentially applied for constructing novel pyrimidine-containing linear molecules. The chemoselectivity of 5-bromo-2-iodopyrimidine ( 1 ) towards Pd-catalyzed coupling reaction serves as a tool for the successful control of the arrangement of dipolar pyrimidine moieties inside the conjugated backbone. The influence of the arrangement of dipolar pyrimidine in the linear backbone on their absorption and photoluminescence are not stupendous. Thermogravimetric analysis (TGA) indicate that all linear molecules in this study exhibit high thermal stability.

11.4: Highly Efficient Blue Organic Electrophosphorescent Devices Based on 3,6-Bis(triphenylsilyl)Carbazole as the Host Material

High-efficiency blue phosphorescent OLEDs using a novel host material of 3,6-bis(triphenylsilyl)carbazole (CzSi) are reported. Devices with the CzSi host and the blue phosphorescent dopant FIrpic show a maximum external quantum efficiency of ∼16% (30.6 cd/A), a maximum power efficiency of 26.7 lm/W, and a maximum brightness of ∼59000 cd/m2.

Highly efficient blue phosphorescent OLEDs using large bandgap host materials

The synthesis and properties of 3,6-bis(triphenylsilyl)carbazole as an effective host material for blue electrophosphorescence are reported. The electrochemically active C3 and C6 sites of carbazole are non-conjugated blocked with the steric, bulky and large-gap triphenylsilyls, the resulting new compound retains the large triplet energy of carbazole yet exhibits much enhanced morphological stability and electrochemical stability in comparison with previous carbazole-based host materials. Using this new host material, blue phosphorescent OLEDs having high efficiencies up to 16%, 30.6 cd/A and 26.7 lm/W are demonstrated.