Synthesis And Photoelectric Properties Of Boron Heteropolyclic Aromatic Organic Small Molecules

Organic light-emitting diodes（OLEDs）have become a key research topic in academia and industry due to their advantages of low cost,low driving voltage,simple operation,flexible display,and fast response time.In the development of the OLED field,the design and research of organic materials is very important.In recent years,researchers have conducted intensive investigations on small organic molecules,which confirmed the superior application prospects of such molecules in organic light-emitting displays.Due to the difficult synthesis of boron-containing polycyclic aromatic hydrocarbons,development is slow:（i）Boron-containing organic compounds are too sensitive to air and water,resulting in poor stability;（ii）Lack of synthesis methods and raw materials for boron-containing organic compounds.To solve these problems,this thesis from the synthesis method of polycyclic aromatic hydrocarbons containing boron,raw materials and construction of D-A type synthesis method and other core issues,synthesis of a series of boron polycyclic aromatic organic compounds,and the preparation of organic compounds containing boron OLED devices.The contents listed as below:（1）Boron-containing compounds were too sensitive to air and water,resulting in the slow development of boron-containing organic compounds.The introduction of boron was mainly boron trihalide reagent,which makes the synthesis methods of boron-containing organic compounds scarce and limits the development of boron-containing organic compounds.Using 7,7-dimethyl-7H-dinaphtho[2,1-b:1’,2’-d]silole（DNSi）as raw material and Fe Cl3 as catalyst,1-BMes compound was synthesized by silicon-boron exchange in a one-pot method.The boron compound is a p-n type material,and the realization of a p-πconjugated system provides for a good fluorescent material.The quantum efficiency of the 1-BMes compound is 24%,the thermogravimetric analysis temperature is 303.8℃,and the glass transition temperature is 76.4℃.The OLED performance application tests revealed a green light emission at 520 nm with CIE coordinates of（0.24,0.49）and a maximum external quantum efficiency（EQE）of 6.2%for the device.The synthesis of the diboron polycyclic aromatic hydrocarbon was based on DNSi as raw material,Al Cl₃was used as catalyst,and MDBDBC compound was synthesized by silicon-boron exchange in a one-pot method.The diboron is a p-n type compound with a p-πconjugated system and good fluorescent light-emitting properties.The quantum efficiency of MDBDBC was determined as 60%,and the thermogravimetric analysis temperature was 380.9℃.The glass transition temperature was not obtained.The device exhibited green light emission at 530 nm with the CIE coordinates（0.33,0.62）,and the maximum EQE was 4.9%.The EQE of OLED devices prepared by monoboron and diboron compounds was greater than that of similar boron-containing organic compounds.The superior performance of 1-BMes over MDBDBC compounds could be attributed to:（i）Twoπplanes in 1-BMes compounds include an angle of33.4°,which results in an easier electron transport than in rigid planar MDBDBC compounds;（ii）MDBDBC compounds contain double boron atoms which have an important influence on the EQE of OLED devices.（2）Carbazole was an electron donor group,but the synthesis of strong electron donor capacity containing polycarbazole was a difficult problem.Aiming at this problem,a bromotrimethylbenzene as raw material undergoes free radical synthesis,and the carbazole undergoes an electrophilic removal reaction to obtain two compounds,DCz MPh and TCz MPh.The obtained compounds were characterized by single crystal XRD,NMR spectroscopy,and HR-MS.For the DCz MPh and TCz MPh compounds,the phosphorescence quantum yield were determined as 0.98%and 3.43%,and their phosphorescence lifetime as 0.27 s and 0.28s in decibels,respectively.Thermogravimetric analysis demonstrated a superior thermal stability of the two compounds.They could be used to create letters for application in anti-counterfeiting materials.The excellent performance of the DCz MPh and TCz MPh compounds can be attributed to:（i）the combination of H-aggregation and heavy atom effects to obtain a longer phosphorescence lifetime;（ii）a large number of intermolecular and intramolecular interactions lead to a relatively small relaxation rate to S0,and the observed ultralong lifetimes of both molecules;（ⅲ）the consequent reduction in non-radiative decay,and the promoting effect of the intramolecular Br bond on the spin-orbit coupling between the excited singlet state and the triplet state.（3）Using 2,2’-dibromobinaphthalene and 9,10-dibromophenanthrene as raw materials under anhydrous conditions in nitrogen atmosphere,a series of silole compounds,such as DMDNSi,DMDPh DNSi,DMODMDNSi,and DMDPh Si compounds,were synthesized in higher yields than previously reported.Characterization methods applied on these compounds included single crystal XRD,NMR spectroscopy,and HR-MS.The series of organic silole blue light-emitting materials exhibited high quantum yields.Four silole compounds were applied in the detection of nitrogen-containing organic explosives.The quenching constant and quenching efficiency of DMDNSi,DMDPh DNSi,DMODMDNSi,and DMDPhe Si were determined as 4.82×104 M^-1and 96%,4.25×104 M^-1and 95.5%,4.62×104 M^-1and 95.1%,and 3.20×104 M^-1and 94%,respectively.The excellent detection performance of TNP could be attributed to:（i）the blue emission wavelength of some silole compounds was relatively close to the absorption wavelength of TNP;（ii）their detection performance is directly related to the space molecule of the compound,and the detection effect was better if the space molecule is small.（4）Using DNSi as raw material and Fe Cl₃as catalyst,BMNTPh A,BMNCz,BMNDPh Cz and BTMNDPh Cz compounds were synthesized by silicon-boron exchange and Suzuki coupling in a one-pot method.The four organic light-emitting materials with D-A structure exhibited better quantum efficiency.In the OLED performance application test for BMNTPh A,the device showed yellow light emission at 582.7 nm with the CIE coordinates（0.44,0.52）and a maximum EQE of 1.4%.In the test for BMNCz,green light emission were detected at 507.6 nm with the CIE coordinates（0.30,0.52）,while the maximum EQE was determined as 2.72%.BMNDPh Cz,the conducted OLED performance application tests of the prepared device revealed green light emission at 507.6 nm with the CIE coordinates（0.35,0.59）and a maximum EQE of 3.5%.In the test for BTMNDPh Cz,green light emission were detected at 502.7 nm with the CIE coordinates（0.30,0.62）,while the maximum EQE was determined as 2.61%.（5）There were few reports on organic boron-containing fluorescent materials emitting red light,which was the difficulty in the synthesis of fluorescent materials.DCz DBA was synthesized with DNSi as raw material and Al Cl₃as catalyst by silicon-boron exchange and Suzuki coupling in one pot method.DCz DBA compound was a new type of D-A-D compound,which could emit red light at long wavelength.The properties of OLED devices and solar cells devices of this compound were tested,and EQE was 1.92%and PCE was13.2%,respectively.good experimental results were obtained.