Construction And Photoelectric Properties Of Aromatic Phosphine Oxide Electroluminescent Materials Based On DA Structure

Organic electrofluorescence materials,especially thermally activated delayed fluorescence(TADF)materials,is a hotspot in the field of organic electroluminescence.The donnor(D)-acceptor(A)system with push-pull electron structure has prominent characteristics in the excited state properties and electrical properties.In this paper,a series of D-A type electroluminescent materials were designed and synthesized by using the electron effect and steric effect of phosphine group(P = O).1.We propose a novel strategy for building efficient blue TADF materials,the weak acceptor-strong donor(WASD)strategy.Useing phenoxazine as strong electron donor and phosphine groups with weak electron-withdrawing ability and interrupted conjugation effect as weak acceptor,a series of highly efficient WASD-type blue TADF dyes have been constructed together and the maximum quantum efficiency reached 15.3%.This work proves that the WASD strategy can effectively suppress the red shift of the spectrum meanwhile enhancing the charge transfer effect by the multi-bipolar action,which is more conducive to the construction of high performance TADF blue dye.2.The diphenylphosphine oxide(DPPO)group with the appropriate electron-withdrawing ability as the second acceptor,with the first acceptor triazine,regulates the electron interaction between triazine and the t-butylcarbazole donor.Through the modification of DPPO,the frontier orbit separation is further improved,and the singlet-triplet spiltting energy(?EST)is further reduced while maintaining the high excited energy level,and its thermal excitation delayed fluorescence characteristics are improved.3.We investigated the effect of interlayer and intralayer exciplexes on the performance of organic electroluminescent devices based on phosphine oxide acceptor molecules.Using the appropriate electron-withdrawing ability and the large steric effect of the DPPO group,the exciton quenching due to the formation of the interfacial exciplex is suppressed by controlling the modified position of the dibenzothiophene and dibenzothiophene sulfone.Meanwhile,the carrier transport balance of the emitting layer is promoted and the efficiency and stability of the device is improved.In addition,triphenyltriazine triphosphine oxide as electron acceptor and 1,3-dicarbazolylbenzene(mCP)as donor form a series of highly efficient blue TADF exciplex.The steric effect of DPPO is moderately combined with its electron-withdrawing ability,and the distance between the acceptors and donors and the electron interaction are finely tuned to decrease the ?EST and keep the emission color of the exciplex.