The Design And Synthesis Of 1,10-phenanthroline Contained Small-molecular Materials For Organic Light-emitting Diodes

OLEDs find important application in flat displays and organic solid-state lighting for the advantages of self-illuminating,fast response and possibility of flexible display.To meet the needs of display devices,further improvements in efficiency and stability of the electroluminescent devices are important,which makes higher demands for materials employed in the devices,such as electron-transport/hole-blocking materials and host materials.1,10-phenanthroline is widely used in organic optoelectronic materials for its planar,rigid and electron deficient structure,such as the common electron-transport/hole-blocking material BPhen,BCP.However,there may exit certain stability problems in high temperature environment for its low glass transition temperature（T_g）.As for 1,10-phenanthroline based host materials,the performance of the phosphorescent devices is far beyond satisfactory.In this dissertation,considering the merits of 1,10-phenanthroline,a serial of1,10-phenanthroline derivatives has been designed,synthesized and characterized for the organic light-emitting diodes.1)A new electron-transport/hole-blocking material Phen-DFP is further presented through replacing m-diphenylphosphinylphenyl in Phen-m-PhDPO with 3-（3,5-bis（2,4-difluorophenyl）-phenyl）phenyl.Phen-DFP possesses simple synthesis and purification procedure and high T_g（⁹5 ^oC）.The multifluorinated moiety lowered the HOMO/LUMO level（-6.6 eV/-3.0 eV）and raised the electron mobilty(?_e≈2.5×10^-5 cm² V^-11 s^-1@E=5×10⁵ V cm^-1).It was evaluated as a potential hole blocker for pin sky blue fluorescent,green and red phosphorescent OLEDs,in comparison with Phen-m-PhDPO and TPBi.Remarkably,the modified DSA-Ph based fluorescent OLEDs that contained Phen-m-PhDPO and Phen-DFP produced a luminous and power efficiency of¹6 cd A^-1 and 13 lm W^-1@1000cd m^-2 with a primitive lifetime t₉₀≈200 h@1000 cd m^-2 under constant current driving.The performance is comparabl to the best MADN:DSA-Ph based sky blue fluorescent OLEDs.2)We demonstrate the exciplex formation between Phen-DFP and the hole-transport material m-MTDATA,and simple devices with yellow-light emitting are fabracated.The devices achieve a maximum luminous efficiency（LE）of 12.8 cd A^-1,power efficiency（PE）of 13.3 lm W^-1,external quantum efficiency（EQE）of 4.4%with a CIE（x,y）of（0.45,0.53）,which indicate the great potential of 1,10-phenanthroline derivatives for OLEDs with exciplex.3)Host materials Phen-m-PhCz and Phen-o-PhCz with simple structure are designed and synthesized,both of which prossess high T_g（¹00 ^oC）and high triplet level.The green phosphorecent OLEDs employing the host materials and green Ir（PPy）₂（acac）emitter achieve promising performance.Remarkably,the Phen-m-PhCz phosphorecent OLEDs with the typical stucture of ITO/MoO₃（5 nm）/TAPC（50 nm）/TCTA（10 nm）/Phen-m-PhCz:8%Ir（PPy）₂（acac）（25 nm）/Phen-DFP（30 nm）/LiF（1 nm）/Al（120 nm）reach a high maximum LE of 102.0 cd A^-1,PE of 112.3 lm W^-1,EQE of 26.1%,and the LE and EQE slightly reduced to99.0 cd A^-1 and 25.3%@1000 cd m^-2,corresponding to a efficiency roll-off of only 2.9%and3.1%,respectvely.It’s worth noting that the performance is among the best green phosphorcent OLEDs ever reported and futher characterization indicated that the exciplex formation at the interface of TCTA and the host may be responsible for the high efficency and small roll-off of the OLEDs.4)Deep-blue fluorescent compounds Phen-p-PhCz and Phen-CzPh-t-Bu are designed and synthesized,both of which are crystalline materials.Phen-p-PhCz and Phen-Cz Ph-t-Bu achieved a maximum LE/EQE of 1.16 cd A^-1/1.38%and 1.23 cd A^-1/1.92%with CIE（x,y）of（0.16,0.08⁰.09）and（0.15,0.05⁰.06）in non-doped deep-blue devices,respectively,and both compounds are also utilized as host material for green Ir（PPy）₂（acac）emitter in phospherscent OLEDs.Remakably,the Phen-p-PhCz OLEDs with stucture of ITO/MoO₃（5nm）/TAPC（50 nm）/TCTA（10 nm）/Phen-p-PhCz:8%Ir（PPy）₂（acac）（25 nm）/Phen-DFP（30nm）/LiF（1 nm）/Al（120 nm）reached a high maximum LE of 80.9 cd A^-1,PE of 101.7 lm W^-1,EQE of 21.3%,and the LE and EQE slightly reduced to 76.2 cd A^-1 and 20.1%@1000 cd m^-2,respectvely.