Synthesis And Characterization Of "Self-Host" Hyperstructured Tadf Light-Emitting Materials By Grafting Triazine Or Naphthalimide-Containing Emitting Units And Host Units Onto Calix Resorcinarene Core

Solution-processed organic light-emitting diodes(OLEDs)have the advantages of high brightness,low energy consumption,fast response,low cost,and large-area production.They have great development prospects in solid-state lighting and flat panel displays,and represent the future development direction of the display technology industry.Thermally activated delayed fluorescence(TADF)materials are considered as“third-generation organic light-emitting materials”and have received extensive attention in recent years,because they can theoretically achieve 100%internal quantum efficiency and do not require noble metal.Now,the reported solution-processible TADF materials mainly include polymers and hyper-strutured molecule(HSM)emissive materials.Polymers have the disadvantages of unclear structure and poor reproducibility,however,as for HSM,it is easy to overcome this problem by binding TADF unit and other functional units with molar ratio to core.Therefore,the development of more effective HSM TADF emissive materials are important.Meanwhile,many high-efficiency green and blue TADF materials have been used in OLEDs,while there are still relatively few high-efficiency red TADF emissive materials due to a wide band gap and higher non-radiative energy loss.Therefore,there are still great challenges in the development of red emitting materials.In this paper,a series of multi-functional yellow-green and red“self-host”TADF HSM emitters CRA-PxzTrz_(x)-TPA_(y)-m CP_(100-x-y)and CRA-NDMAC_(x)-m CP_(100-x)were synthesized via click reaction,reactively.¹H NMR,MALDI-TOF MS,FT-IR,EA,GPC,DSC,TGA,XRD,AFM,UV-Vis,PL and CV were used to characterize the chemical structure and properties of intermediates and target molecules.The non-doped solution-processed OLEDs were prepared by spin-coating,and its performance was measured.Part 1,Synthesis and characterization of multi-functional hyper-structured molecular emitters CRA-PxzTrz_(x)-TPA_(y)-m CP_(100-x-y).First,three azide-containing functional compounds PxzTrz-N₃,TPA-N₃,m CP-N₃,and alkyne-containing core CRA-Alkyne were synthesized.Then,according to the calculated feed ratio,a series of multi-functional HSM emitters CRA-PxzTrz_(x)-TPA_(y)-m CP_(100-x-y)(x=87.5,87.5,75,62.5and 50,y=12.5,0,12.5,12.5 and 25,here,x and y represent the proportion of PxzTrz-N₃ and TPA-N₃ among the total azide-containing compounds,respectively)were synthesized via click reaction between functional compounds and core.¹H NMR,MALDI-TOF MS,FT-IR and EA results indicated that the target products are successfully synthesized.GPC showed that the molecular weight distribution of the target products is narrow,and the polymer dispersion index(PDI)is in the range of1.08?1.12.TGA and DSC displayed the target products have good thermal stability with high decomposition temperature(T_d>355°C)and glass transition temperature(T_g>119°C).XRD and AFM showed that the target products are in an amorphous state and have good film-forming properties,respectively.When using CRA-PxzTrz_(x)-TPA_(y)-m CP_(100-x-y)as undoped solution-processed emitting layer the devices based HSM with TPA shows higher maximum luminance and EQE than those devices based HSM without TPA.The CRA-PxzTrz_(87.5)-TPA_(12.5)-m CP₍₀₎-based device showed a maximum luminance of 4869 cd/m² and maximum EQE of 3.3%.The CRA-PxzTrz₍₇₅₎-TPA_(12.5)-m CP_(12.5)-based device showed a maximum luminance of 5132 cd/m² and maximum EQE of 2.9%.Part 2,Synthesis and characterization of red“self-host”hyper-structured molecular emitters CRA-NDMAC_(x)-m CP_(100-x).First,the azide-containing red functional compounds NDMAC-N₃ was synthesized.Then,according to the calculated feed ratios,a series of red“self-host”hyper-structured molecular emitters CRA-NDMAC_(x)-m CP_(100-x)(x=0,12.5,25,50,75,87.5,100,here x represent the proportion of NDMAC-N₃ among the added azido compounds)were synthesized via click reaction between the alkyne groups of CRA-Alkyne and azide groups of NDMAC-N₃ and m CP-N₃.¹H NMR,MALDI-TOF MS,FT-IR and EA results indicated that the target products are successfully synthesized.TGA and DSC showed the target products have good thermal stability with high decomposition temperature(T_d>355°C)and glass transition temperature(T_g>137°C).XRD and AFM indicated that the target products are in an amorphous state and have good film-forming properties,respectively.Using CRA-NDMAC_(x)-m CP_(100-x)as emitting layer,the undoped solution-processed OLEDs emitted red light.Among them,the devices based on CRA-NDMAC₍₂₅₎-m CP₍₇₅₎showed the best performance with a turn-on voltage of 6.0 V,maximum luminance of 212 cd/m²,current efficiency of 2.5 cd/A and maximum EQE of 1.6%.