The Theory Of Linked Styrene Blu-ray Materials Research And Structural Design

Organic light-emitting-diode(OLED) is the new generation falt display which has taken on attractive prospects on application, and is the research hotspots of falt display and electroluminescence at present. Distyrylarylenes derivatives was deemed to be a kind of better blue light-emitting materials than other kinds. Jeon and his companions synthesized a new kind of distyrylarylenes "4-[(1,2-diphe-nyl)-4 -(N,N-diphenyl-4-vinylbenzenamine)]" (A) biphenyl which was used as a dopant in emitting layer to acquire high purity blue light-emitting diode in 2007. In order to give a reasonable explain for luminescent properties of compound A, and to design more excellent blue light-emitting materials, it si necessary that to give theoretical study of electronic structure and Spectral properties for compound A and its substituted derivatives, analogues. Based on the above purpose, at first, we designed nine kinds of derivatives replaced by fluorin (-F) and triflouro (-CF₃), at second, we designed seven analogues by changing the biphenyl of main chain. We carried out a systematic study of the theoretical calculation for compound A and sixteen kinds model compounds by the methods of ab initio HF and density functional theory B3LYP. On the basis of the optimized geometry structure, electronic absorption and emission spectrum have been calculated with the time-dependent density functional theory (TD-DFT) and CIS in order to discuss the relation between the electron transition mechanism and the spectrum properties. It is found that the position or number of the substituent is different can change the energy level of molecular orbitals, and the mian chiain in the middle of molecule is changed the energy level of molecular orbitals and spectral properties. The means that explore the relationship of structure and sroperty to provide crediblecredible for related experimental research .The detailed contents of our study are in the followings:Firstly, we took the theoretical for electronic structure and spectral properities for compound A and its nine kinds of derivatives, conclusions are as follows:(1) The strength of main emission peak at 465-474nm blue-light scope is far more than the second emission peak at 372-387 nm, which is one reason that the compound A have the high purity blue -light-emitting.(2) The emission wavelength of substituted derivatives on the benzene of themain chain by four -F and four -CF₃(B1 and B2) is blue shift.(3) The substituted derivatives on the benzene of themain chain (B, B1, B2 C, D, D1, D2) cause an energy lowering of the lowest unoccupied molecular orbital (LUMO) energy levels obviously, which facilitates the injection of electron carriers from the metal electrode.(4) Substituted derivatives on the benzene of benzenamine (D, D1, D2 and E) cause an energy lowering of the highest occupied molecular orbitals (HOMO) obviously. The increasing of IP and energy gap, which is proper to hold hole transfer from theemission layer to the electron transport layer, reduces the formation of exciplexes at the interface and causes a blue shift of spectra.(5) The substituted derivative of benzene on both the main chain and benzenamine (D, D1, D2) is better for a balance of electron and hole injection which should result in even better emission properties.Secondly, the electronic structure and spectral properties of analogues of A were investigated, conclusions are as follows:(6) We found that the HOMO energy level was increased by replaced the biphenyl of main chain, replaced by pyrrole, thiophene and furan(H2-H4), the HOMO energy level was increased obviously, which is propitious to hole transfers.(7) The absorption spectras of compounds which the biphenyl of main chain replaced by fluorine, carbazole, dibenzo[b,d]thiophene and dibenzo[b,d]furan(G1-G4) are bule shif, but their emission spectra are red shif , so their stokes shift is increase, and have excellcet fluorescent characteristic. The absorption and emission spectra of compound H2-H4 are all red shift, obviously.