Design And Synthesis Of DA Organic Blue Fluorescent Material Based On Pyrene And Research On Its Electroluminescence Performance

In recent years,organic light emitting diode(OLED)has attracted increasing attention in the fields of flat panel display and solid-state lighting due to their characteristics of light in weight,convenience,and flexibility.Organic emitting-materials play the key role in determining the performance OLED.After more than 30 years of continuous efforts by researchers,red and green emitting materials have basically met the requirements for commercialization in terms of efficiency and stability.However,the efficiency and lifetime of blue emitting materials cannot be improved,which severely hindered the industrialization of OLED.This dissertation focus on developing new types of organic blue fluorescent material and explore its device performance.This paper includes the following three parts:First,by introducing the electron donor(D)and electron acceptor(A)unit,we successfully constructed two novel bipolar(D-A)blue fluorescent emitters.The details are as follows:First,a phenyl group is introduced as the A unit or D unit at the 1,3-active site of pyrene,then a 4-methoxyphenyl group or a 4-formylphenyl group is introduced into the 5,9-K region as the D or A unit and we successfully synthesized two D-A type molecules 5b(1,3-A/5,9-D)and 5c(1,3-D/5,9-A).Compared with the non-D-A type 5a,5b and 5c have smaller molecular energy gaps,possessing intramolecular charge transfer(ICT),and have higher fluorescence quantum efficiency.Based on this D-A type structure,we precisely tuned the color of these molecules in organic solvent.Interestingly,these two molecules exhibited deep blue fluorescence emission both in the non-doped and doped films.Second,based on our previous work,a series of D-A type blue fluorescent emitters(2b-d:1,3-A/5,9-D;2e-g:1,3-D/5,9-A)were synthesized by changing the type of D/A units in the 5,9-K region.These materials exhibited good thermal stability(Td>300).Compared with the non D-A type 2a,the absorption and emission spectra of the 2b-d and 2e-g exhibited bathochromic shift,resulting from the ICT characteristics of these D-A type molecules.As for 2b-d(1,3-A/5,9-D),2d exhibited the largest red shift,which could be attributed to the strong electron-donating property of the methoxy units;as for 2e-g(1,3-D/5,9-A),2g exhibited the largest red shift resulting from the strong electron-withdrawing properties of formyl units.We found that by adopting the 1,3-D/5,9-A structure,we could tune the color of molecules in solvent more easily compared with 1,3-A/5,9-D,due to the stronger ICT properties.Third,we studied the OLED performance based on 5a,5b and 5c.Firstly,with 5a/5b/5c as the dopant emitter and CBP as the host materials,we fabricated three deep blue OLED devices with maximum external quantum efficiency(EQE)of 3.33%,2.97%,and 2.48%,respectively.The y value of CIE chromaticity coordinates were all less than 0.10.Then,with 5a/5b as the host material and DSA-Ph as dopant emitter,two highly effective sky blue OLED devices were obtained with EQE of 8.04%and 6.89%,respectively.These results showed that this series of molecules are potential candidate for deep blue OLED devices.