Preparation And Optoelectronic Properties Of Aggregation-induced Emission Polymers

After over 30 years of development,organic light-emitting diodes?OLED?have been commercialized with advantages such as excellent image quality,large viewing angle,being light and thin.In recent years,with the trend in OLED applications shifting to large size display or flexible display fields,polymer OLED?PLED?have attracted much attention.PLED possess distinctive merits such as low-cost wet fabrication process and ease of fabrication which enable them a promising application prospect.Up to now,the majority of PLED are based on aggregation-caused quenching?ACQ?photoelectric polymer.Therefore,to avoid concentration quenching,the proportion of luminous groups in polymers for PLED is controlled in a low degree,typically lower than 20%.However,most of those ACQ PLED are faced with the problem of high efficiency roll-off which limits the application of PLED.At present,there are few researches on PLED based on aggregation-induced emission?AIE?polymers,and the performances of PLED need to be further improved.The main research content of this thesis is to design and synthesize a series of AIE polymers with novel luminescent properties.In addition to the determination of physical properties,chemical properties and photoelectric properties,the polymers are used as emitting layers?EMLs?to prepare PLED by solution process.The design idea of this thesis is to find suitable AIE molecules and copolymerize them with carbazole or fluorine with flexible chains to obtain AIE polymers.The AIE molecules act as luminescent groups while the carbazole or fluorine with flexible chains act as auxiliary group to increase the solubility of the polymers.In chapter one,the development of OLED is introduced followed by the development of PLED and polymers used to construct PLED.Then the development of AIE is introduced,mainly including the synthesis and the applications of AIE polymers.In chapter two,AIE molecule TPE-DPA was used to construct AIE polymers p TPE-DPA-Cz and p TPE-DPA-Flu by Suzuki-Miyaura polycoupling reation.In addition to excellent film forming ability and thermal stability,the resultant polymers exhibit photoluminescence quantum yields?PLQY?reach up to 63.3%and 59.7%,respectively.The PLED using p TPE-DPA-Cz and p TPE-DPA-Flu as EMLs could achieve maximum external quantum efficiency?EQE?of 3.26%?doped EML?and current efficiency of 3.69 cd A^-1?non-doped EML?.Furthermore,all the devices exhibit a quite low efficiency roll-off,indicating that AIE polymers could be ideal candidates for the construction of high performance PLED with low efficiency roll-off.Then in chapter three,an AIE molecule DBT-BZ-PXZ with thermally activated delayed fluorescence?TADF?characteristic was used to construct AIE polymer p DBPF.In addition,TPE-DPA was also introduced to change the polymers emission colour by adjusting the proportion of DBT-BZ-PXZ and TPE-DPA in polymers,and three AIE polymers,p DBPTDF-1,p DBPTDF-2 and p DBPTDF-3 were synthesized.Due to the complex configuration of the polymers,the electron cloud of HOMO and LUMO cannot be separated effectively,and the resultant polymers do not exhibit TADF characteristic.These polymers also possess excellent film forming ability and thermal stability,and the maximum PLQY in THF/water mixture achieves 11.3%.Therefore,it is a promising strategy to construct color-tuned and well-performance PLED based on these AIE polymers.