Heteroatom Modification And Performance Regulation Of Aromatic Phosphine Oxide Photoelectric Functional Materials

High efficiency blue electroluminescent devices are still the current focus of organic electronic display materials and devices.Particularly,the development of host and guest materials for blue emissions with high excited state energy and favorable carrier injecting and transporting ability is always paid much attention.In this thesis,we modified the optoelectronic properties of aromatic phosphine oxide compounds through involving heteroatoms for high excited levels and favorable charge transport properties.According to this design strategy,we successfully synthesized a series of aromatic phosphine oxide materials,including:According to"short-axis linkage"strategy,SFXSPO,SFXDPO,SixantSPO and SixantDPO were prepared on the basis of SFX and 10H-dibenzo[b,e][1,4]oxasiline as core.Compared to spiro-fluorene analogues,their triplet energy（T₁）was dramatically improved to 3.0 eV,accompanied with good thermal stability with the temperature of decomposition（T_d）around 310-375 ^oC.Similar,10H-phenoxazine and 10H-phenothiazine were employed as core to construct PXZPSPO,PXZPDPO and PTZPSPO with diphenylphosphine oxide（DPPO）substituted at ortho-positions for improving excited energy and carrier injecting and transporting performance,whose T₁ were 2.82,3.17 and 3.19 eV,respectively,as well as high T_d of 350-427^oC.In virture of electron withdrawing effect of phosphine oxide groups,D-A type thermally activated delayed fluorescence（TADF）materials were constructed with10H-phenoxazine and 10H-phenothiazine as donor and phosphine oxide as acceptor for emission color tuning.All of the resulted materials SPXZPPO,DPXZPPO,TPXZPPO,SPTZPPO,DPTZPPO and TPTZPPO showed the sky-blue emissions with peak wavelength around 470 nm.The Gaussian simulation showed that the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals of these molecules were remarkably separated to form the stable intramolecular charge transfer excited states.Simultaneously,the increase of the number of donor groups did not change the emission color,reflecting the advantages of phosphine oxide groups with conjugation blocking and moderate electron-withdrawing effect for blue TADF material constrution.