Fluorinated Beryllium Complexes As Multi-functional Electroluminescent Materials

Organic light-emitting diodes(OLEDs) have been researched for decades so farand the development was quick in recent years. Several small size full-color flat paneldisplays such as mobile phones and MP3s have already launched into the marketsuccessfully, indicating the possibility of commercialization for OLEDs. However,despite tremendous improvements have been made by now, there are still challengesassociated with device stability and cost. In this sence, the employment ofmulti-functional organic electroluminescent(EL) materials is a promising approach tosimplify the device structure, thus OLEDs with lower cost and higher stability can beachieved. We designed and synthesized a series of fluorinated beryllium complexes,they can be synthesized and tuned easily, which show great potential in theapplication of commercial OLEDs.1. In chapter II, we designed and synthesized three fluorinated berylliumcomplexes of Be(FPP)2， Be(FBTZ)2and Be(PPF)2. We used NMR, massspectrometry, elemental analysis to determine their molecular structures. We studiedthe crystal structures of Be(FPP)2and compared it with BePP2，which revealed thatthe introduction of fluorine atom can affect the molecular interactions thus leading tothe differences of properties.2. In chapter Ⅲ, we discussed their physical, electrochemical, thermal properties,density functional theory(DFT) and charge transporting ability(TOF, SCLC)properties. Experimental values revealed that these complexes showed great EL properties. high thermal stability can prevent them from decomposing during theprocess of vacuum deposition as well as device working; these materialspossess highenergy bandgap (Eg) which can be used as host materials; high charge transportingability were found during the TOF measurement, it is remarkable that these materialscan act as charge transporting materials; the properite LUMO energy level impartthese complexes better electron injection ability.3. In chapter Ⅳ, these complexes were employed as electron transportingmaterials(ETLs) in a series of phosphorescent OLEDs. Green, yellow and redphosphorescent OLEDs with low turn-on voltages and high efficiencies were obtained.We also fabricated a series of white OLEDs by employing these materials as ETLs, itis notable that these complexes can be employed as high performance ETL in OLED.4. In chapter Ⅴ, we fabricated phosphorescent OLEDs employing thesecomplexes as host materials. These OLEDs exhibited high efficiencies and highstability. In order to obtain more balanced charge transporting ability, unipolartridentate Ir complexes were employed as dopants and high efficiencies were realized.These complexes can also be used as effective host for fluorescent device.5、 In chapter VI, we fabricated phosphorescent OLEDs employing thesecomplexes as emitting materials. These OLEDs exhibited blue emitting and highefficiencies can be realized.In summary, novel beryllium complexes have been designed and synthesized,their physical, electrochemical and thermal properties are discussed in this paper. Inaddition, green, yellow, red and white phosphorescent OLEDs employing thiscomplex as ETLs were tested. Because of the high ET, high Eg, low-lying LUMOlevel and high electron transport mobility, all devices exhibit both low turn-onvoltages and high efficiency.