Synthesis Of Silicon-containing Blue Emission Small Molecules For Organic Light-Emitting Diodes

High efficiency,high color purity and long operation time of blue devices are the key factors for commercialization of OLEDs.In this thesis,groups such as diphenylamine,carbazole,phenanthroimidazole,terphenyl,trimethylsilyl,tetraphenylsilyl,and triphenylsilyl are used as structural moieties to construct efficient silicon-containing blue light-emitting materials through controlling the number of units,tuning the linkage positions and changing the spacers between groups.These methods can efficiently control the thermal,photophysical,electrochemical properties and charge transporting abilities.This thesis provides feasible methods for the design of highly efficient blue emitters.1. A series of D-?-A fluorophores,Ph BPI,D2SPPI,CPh BPI,and C2SPPI was synthesized by using diphenylamine,carbazole,terphenyl,phenanthroimidazole as the moieties and terphenyl as the linking bridge with trimethylsilyl substitution.On the one hand,terphenyl bridges extend the degree of conjugation.On the other hand,the distortion of terphenyl itself weakens the charge transfer effect between the electron donor and acceptor.Furthermore,the further introduction of trimethylsilyl on the terphenyl bridged motifs can not only block the degree of conjugation and blue-shift the emission of the luminescent materials,but also improve the thermal stability and solubility of the molecules.These molecules show fluorescence in blue or deep blue region with high color purity and high triplet energy level,and thus can be used as a fluorescent/phosphorescent hybrid white light-emitting materials.2. In this chapter,two bipolar blue-emitting materials DSi PPI and CSi PPI were designed and synthesized by tetraphenylsilane-centered molecules with diphenylamine/carbazole as electron-donating group and phenanthroimidazole as electron-withdrawing group.The thermal stabilities and optoelectronic properties of the materials were investigated.Both luminescent materials show good thermal stability,and emit voilet-blue light.The optimal blue fluorescent OLED device was prepared using DSi PPI as a dopant in m CP and exhibited high maximum external quantum yield(EQE_max),current efficiency and power efficiency of 7.07%,2.57 cd A^-1,and 2.12 lm W^-1,respectively,showing deep blue emission with CIE_x,y?0.167,0.078?at 100 cdm^-2.3. Spirobifluorenes are structurally orthogonal and non-planar2,2',7,7'-tetrakis?triphenylsilyl?spirobifluorene?TPSP?was designed and synthesized by introducing four large steric hindrance group onto spirobifluorene.This novel molecule was spherical and the conjugation was confined to the spirobifluorene core.Its glass transition temperature and thermal decomposition temperature are as high as 150°C and 539°C,respectively.With TPSP as host material,electrophosphorescent OLEDs doped with Ir?ppy?₂acac,PO-701,Ir?piq?₂acac,and Ir?dpm??piq?₂ were fabricated and measured with maximum external quantum yields of 21.1%,19.5%,10.5%and 10.7%,respectively.