Theoretical Study On The Intermolecular Interaction And Charge Transport Properties Of Heteroatom-containing Acene Compounds

As a typical organic photoelectric material,acene compounds have a wide range of applications in organic devices due to their high carrier mobility.The stability of acene-based molecules in the environment is poor,and the introduction of heteroatoms in the π-conjugated system changes the electronic structure of the molecule,which in turn changes the packing structures in the solid.It was found in the study that the non-bonding interactions between π-conjugated systems are crucial for designing and improving the packing structures and electron transport properties of the molecules.The intermolecular interactions affect the effective transport of charge between molecules and the reorganization energy of molecules.In this dissertation,heterocyclic compounds are used as the research object.Through the calculation of intermolecular interaction energies(IEs)by different gradient density functionals(DFT),the appropriate DFT functionals and basis sets are selected.At the same time,taking the heteroatom substituted picene as the research object,the effects of heteroatoms on the molecular structure,crystal packing patterns,intermolecular interaction energies,and molecular reorganization energies were studied to find out the factors causing the difference in carrier mobility due to different heteroatom substitutions.The main contents of the article are briefly described as follows:The first chapter of this article mainly introduces the advantages of organic optoelectronic materials and the progress of research on acene-based molecules.Through the investigation of acenes,it was discovered that the inclusion of heteroatoms in the π-conjugate backbone of isolated molecules can improve the structure of molecules and interaction between molecules.The role and the change of carrier transport properties of solid materials can also reduce the vibrational energy of molecules and increase the stability of molecules.Also,the performance evaluation parameters of organic semiconductors and the effect of heteroatom substitution on the molecular structure,molecular interaction energy,and charge transport properties are introduced.The second chapter mainly introduces the methods of the common intermolecular interaction energy and carrier mobility involved in calculation.This paper introduces the advantages and disadvantages of the first-principle and the force field methods to calculate the intermolecular interaction,as well as the intermolecular coupling integrals,the internal recombination energy and the external molecular recombination can be used in the model and calculation methods.In the third chapter,we take 23 heterocyclic dimers as the research objects,and select the methods and basis set for accurately calculating the interactions of heterocyclic molecules.The results show that dispersion correction is essential in accurately describing weak intermolecular forces.In the 20 functionals considered in the study for the calculation of IE values,the meta-GGA gradient performs best with the VV10 correction function ωB97M-V;the addition of semi-empirical dispersion correction to the DFT can accurately describe the intermolecular non-bond interaction forces,and can reduce the cost of calculations.The results of different basis set have shown that the use of the cc-pVTZ basis set for the calculation of the interaction between heterocyclic dimers can also yield reliable results and reduce the computational cost.However,the use of the cc-pVTZ basis set must be considered CP correction to reduce the basis set superposition error.In the fourth chapter,the chalcogen-substituted picene molecules are mainly used as research objects to study the molecular structure of heteroatoms,the packing arrangement of crystal structures,the reorganization energy and the carrier mobility,and to reveal the possible causes of the differences in carrier mobility.The results of the study indicate that heteroatom substitution of the picene heterocycle molecule(DNE-W)causes changes in the molecular structure and also changes the packing form of the molecule in the crystal.From the molecular frontal orbital energy level diagram,after the doping of S and Se atoms,the HOMO and HOMO-1 orbits are almost degenerate,which increases the probability of hole transport.The change in the distance between molecules leads to a corresponding change in the interaction between the molecules,resulting in a change in the hole transfer integral.However,with the substitution of heteroatoms,the doping of different molecules leads to a different degree of reduction of molecular external reorganization energy,resulting in a change in the carrier mobility.