Synthesis Of Aggregation-Induced Delayed Fluorescence Luminogens Containing Carbonyl Groups And Their Application In Organic Light-Emitting Diode

As a new generation of display technology,organic light-emitting diode(OLED)has received much attention due to its numerous advantages such as high contrast,fast response,low power consumption,wide viewing angle,and flexibility.High-efficiency OLEDs are inseparable from high-performance luminescent materials.However,traditional luminogens often suffer from severe"aggregation-caused quenching"(ACQ)problem in aggregated state,which greatly limits their practical application.In contrast,aggregation-induced emission(AIE)materials exhibit higher fluorescence efficiency in aggregated state compared with dispersed system.AIE luminogens(AIEgens)have realized remarkable electroluminescence(EL)performances on OLEDs in recent years.Nevertheless,there are still some problems that are worthing exploring.For example,the efficient AIEgens,especially high-performance blue-emitting AIEgens are still scarce and need to be further explored,and multi-functional materials with AIE characteristics are also urgent to be developed in OLEDs.Based on the above reasons,the main research work of this paper are as follows:In Chapter 2,we design and synthesize several new aggregation-induced delayed fluorescence(AIDF)luminogens containing carbonyl groups and chlorine atoms.These materials exhibit strong spin-orbit coupling(SOC)interactions,fast reverse intersystem crossing(RISC)rates and high fluorescence quantum yields(?_Fs).Their non-doped OLEDs achieve excellent EL properties of the maximum current efficiency(?_C),power efficiency(?_P)and external quantum efficiency(?_ext)of 76.6 cd A^?1,75.2 lm W^?1 and 21.7%,respectively.Even at the luminace of 1000 cd m^?2,the?_ext is still close to 20%,indicating small efficiency roll-off.Furthermore,they also perform remarkable in doped OLEDs in a wide doping concentration range(5?90 wt%),and the maxmmum?_ext reach 29.1%,revealing excellent manufacturing process tolerance and great practical application potential.In Chapter 3,to further explore the influence of halogen atoms on the properties of AIDF materials,we design and synthesize a series of novel AIDF materials containing carbonyl groups and bromine atoms.These molecules show different?_Fs in neat film,which are mainly contributed to the heavy atom effect caused by the bromine atom as analyzed by theoretical calculation and experimental results.OLEDs employing 3-BCP-BP-PXZ as emitter are fabricated due to its outstanding photophysical properties,giving the maximum?_ext of 19.5%and 28.6%for non-doped and doped devices,respectively.These results provide theoretical and experimental proofs to design high-efficiency AIDF materials.In Chapter 4,in order to construst blue-emitting AIEgens and achieve high-performance OLEDs,three novel AIE molecules using acridone unit as electron acceptor are synthesized by molecular engineering.These luminogens possess typical quasi-equatorial conformers(QECs),which can effectively facilitate the separatation of highest occupied molecular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO),resulting in tiny singlet-triplet energy splitting(?E_ST).On the other hand,the SOC effect can also be improved by the n??^*transition from lone pair of acridinone group,which further accelerates RISC process of triplet excitons.High?_Fs of 78.0?93.6%are obtained for their doped films.Non-doped and doped OLEDs are fabricated based on these molecules.Their non-doped devices realize high?_ext of 16.6%,with small efficiency roll-off at the luminance of 1000 cd m^?2.Their doped OLEDs show blue emission with EL peaks of 482?492 nm,and prominent EL performances of 59.2 cd A^?1,66.4 lm W^?1 and 26.8%.These results afford new approach to design and synthesize high-performance blue-emitting AIEgens.In Chapter 5,several novel AIEgens with deep-blue emission,namely PIPD-MP-DPA,PIPD-MP-IMDB,PIPD-MP-DMAC and PIPD-MP-DPAC are designed and synthesized.They have good photophysical characteristics,thermodynamic properties,and high solid?_Fs.Their non-doped OLEDs show deep-blue emission with EL peaks of 418?438 nm.The device based on PIPD-MP-DPA exhibits excellent EL performances that the maximum?_extattains 4.4%,and the CIE coordinates are only(0.154,0.078),as well as a narrow half-peak width of 56 nm.On the other hand,owing to the good carrier transport ability of PIPD-MP-DPA and PIPD-MP-IMDB,phosphorescent OLEDs(Ph OLEDs)are fabricated by employing them as host,affording super?_ext of 25.9%,28.0%and 14.0%for green,orange and red Ph OLEDs,respectively.In addition,we also construct hybrid white OLEDs(WOLEDs)based on PIPD-MP-DPA,giving the high?_ext of 21.6%and 16.3%for two-color and four-color WOLEDs,respectively.In brief,these new AIE molecules can be used as emitters for high-efficiency fluorescent OLEDs,and host for phosphorescent and white OLEDs,promoting the development of AIE materials in OLEDs.