Dft Study Of The Structure And The Reorganization Energy Of Organic Small Molecule Hole Transport Materials

Electron transfer is one of the prototypical chemical reactions.Which isubiquitous in chemistry, physics, biology and material science. In the last decades thestudy of electron transfer reactions was very actively pursued both theoretically andexperimently. Understanding and control of electron transfet reactions comprise one ofthe broadest and most active research areas of physical chemistry today.Nowadays, theoretical researchers of electron transfer reaction mainly forcus ontwo aspects: One is the development of the theoretical methods, which includessemi-classical extensions of the classical formalisms as well as quantum-mechanicaltreatments. The other is application of the electron transfer theory in the new fields.Although classical Marcus theory has achieved great success in dealing with manyinorganic systems, many of its basic assumptions may not be valid for many newreaction systems in many cross areas between chemistry and other science, such asclosely coupled organic transfer-transfer reactions and long-range electron transferreactions in biological systems. These indicate the further need for the theoreticalresearchers of electron transfer reactions.The hole–hopping process in a molecular material ,however, can also bedepicted as an electron-transfer reaction in which an electron is exchanged betweentwo neighboring moleculars,one being in the nertral state and the other being in theradical-cation state.The mobilities of electron and hole are important in optimizing theperformance of OLED device;high mobilities reduce the resistance of the deviceleading to high power efficency.In addition, the relative mobilities of electron and holein the the same material can also affect the power efficency. In this thesis,allcalculations are performed at the density functional theory(DFT) level with B3LYPfunctional,involving the gradient correction of the exchange functional by Becke andthe correlation functional by Lee,Yang and Parr. We use the 6-31G** split valence pluspolarization basis set ;all the calculations are performed with the GAUSSIAN98program.Marcus theory can be used relate the hole mobilities to the reorganizationenergy λ.In this work ,we invesigate the geometric and electric structures as well asthe reorganization energy of TPD and its derivatives,in additions to triphenylamine,biphenyl and their derivatives.The main results of our calculations are below: (1)It seems that it's not biphenyl segement but triphenylamine that playing amajor role in the TPD. At least, we think our results are true when choseλas theparameters to study molecular's properties. (2) It is also concluded that the chemical modifications on TPD's side phenylcould induce the variety of the reorganization energy. And this is attributed to theinteraction of inductive effect and conjugated effect .Electron withdrawinggroup ,positive conjugated effect of substituents choice at the meta-position andnegative conjugated effect of substituents choice at the para-position will decrease thereorgnization energy of TPD. While, Electron donating group ,negative conjugatedeffect of substituents choice at the meta-position and positive conjugated effect ofsubstituents choice at the para-position will increase the reorgnization energy of TPD. (3) It is also concluded that the chemical modification of the central biphenylmoiety of the TPD could induce the variety of the reorganization energy. And this is...