Synthesis And Characterization Of Bis(3,6-Two Aryl Carbazole) Derivatives Based On Alkyl Terminus

As we know,OLEDs have the advantages of Self-luminous,flexible manufacturing and large-area fabrication,which can meet the needs of our people in some special situations.Today,more and more companies and research institutions are begining to study the OLED in the world.However,these companies and research institutions have very little research on uv-oled.In this paper,we synthesized a series of functional materials aiming at the characteristic of the low external quantum efficiency of UV-OLED,and then we test the characteristics of the device.Carbazole is one of the common luminescent materials in OLEDs.Carbazole has a wide energy gap,ET=3.02e V,and its 1,3,6,8,9-positions are easily replaced.In 2011,our team synthesized 9-ethyl-1,3,6,8-tetraphenyl carbazole and demonstrated 3.3%EQE.On this basis,we adopt alkyl and benzyl to connect Two carbazole molecules by9-position,and the conjugation effect of the molecule will be smaller.In this way,it will reduce the formation of exciplex,which can improve Spectral purity of devices,thus to improve EQE.At the same time,these materials have a large molecular weight and a long flexible carbon chain,which improve the thermal stability of the material and makes it easy to prepare the thin film through the spinning process,simplifying the fabrication process of the device.In this paper,we designed twelve functional layer materials used for organic ultraviolet luminescence on the basis of the research in our laboratory.And then,we calculated the HOMO and LUMO of the series of materials and the width of their forbidden band used gaussian.The calculation showed that the series of molecules we designed meet our requirements.But we just got eleven compounds because of the solubility of compoemds itself.After determine the structure of the materials,we characterize the properties of the materials.The absorption spectrum of the solution is 294~308nm,and the maximum emission wavelength of the emission spectrum is 379~394nm.The absorption spectra of the thin film of compound 2a were red shifted 4nm compared with that of the absorption spectrum in solution,and the emission spectrum red shifted13nm.Glass transition temperature of the largest material is 2c,it is 153.5?;Pyrolysis temperature of the largest material is 2d,it is 486.0?;The lowest of the HOMO is-5.32eV,the highest is-5.08eV,the lowest LUMO is-2.19eV,the highest is-1.91eV;The biggest fluorescent efficiency is 60%.On the part of the device,the device performance of 1a,2a,1d and 2d is better.We prepare devices using compound 1a,2a,1d,2d as luminescent layer,and their spectral wavelength is410nm~420nm,and the half-wave width is around 55nm.The device performance of compound 1d is the best,with the maximum luminance of 689cd/m~2 and the maximum current efficiency:0.19cd/A;The maximum external quantum efficiency is0.35%.