| Organic semiconductor(OSC)materials are widely used in organic optoelectronic devices such as organic field-effect transistors and organic light-emitting diodes because of their ease of processing and synthesis,low cost,and good flexibility.Among them,derivatives of acene molecules are the most common.In order to solve the problem of the molecular instability caused by the increase of the number of benzene rings,a new strategy to extend the conjugation length through cyclobutadiene was proposed.Using cyclobutadiene as a linker to connect multiple aromatic rings(fused aromatic rings)can increase the molecular conjugation without reducing the stability of the molecule.In this paper,the multi-scale methods combined with molecular dynamics simulation and Monte Carlo simulation and quantum nuclear tunnel model were employed to study the effect of(using benzocyclobutadiene)modification of triisopropylsilylacetylene-azabenzo series(TIPS-acene for short)on the carrier transport properties,aiming to reveal the role of cyclobutadiene fragments in charge transport,and to seek molecules design strategies to improve the charge transport performance.Theoretical calculations and analysis show that the introduction of benzocyclobutadiene can enhance the chemical stability of the molecule,the balance of the hole and electron transport to some extent,and make unipolar transport molecular materials become bipolar transport materials.The introduction of benzocyclobutadiene also enhanced the thermal disorder effect in the charge transport process,this effect further strengthened the change of molecular transport type(transition from n-type to p-type and bipolar transport).The main conclusions and innovations of this study are as follows:1.The molecular packing pattern in the crystal is closely related to the position of the TIPS branch.The ratio R of the distance between the long side and the short side of the skeleton with the junction of TIPS branches as the boundary point determines the molecular packing mode in the crystal.2.Although the introduction of benzocyclobutadiene will reduce the electron transfer integral value of the molecule to varying degrees,it also increases hole transfer integral value of the molecular,for example,comparing a3,e1 / e2 and a3~*,e~*,the introduction of benzocyclobutadiene makes the transfer integral value of holesand electrons approach,which makes molecules a2 / a3,e1 / e2 have a tendency to become bipolar transmission.3.The influence of non-local electron-phonon coupling effect caused by thermal fluctuation on transmission is analyzed,and it is shown that thermal fluctuation effect contribute to the bipolar transport of benzocyclobutadiene-containing molecules(except e2),especially in a2 molecules.The non-local electron-phonon coupling caused by thermal fluctuations promote both hole and electron transport process and further enhances the bipolar transmission behavior.4.For the molecules a1-a3 containing benzocyclobutadiene,the isotropy of the electron transport gradually increases with the addition of the benzene ring on the right side,which is conducive to two-dimensional electron transport;The increase of the pyrazine ring also plays a role in enhancing the anisotropic of the electrons and holes transport.The introduction of benzocyclobutadiene on one side of TIPS-acene enhances the isotropy of hole transport;bilatrral symmetry introduced benzocyclobutadiene enhances the anisotropy of hole transport.We explored the changes in physical parameters surrounding transmission properties caused by the introduction of benzocyclobutadiene into an acene system,including changes in intra-and intermolecular interactions in this study,and provide a deep understanding of the role of benzocyclobutadiene in designing organic semiconductor materials from a microscopic perspective.It is hoped that some useful clues and molecular design strategies for the design and synthesis of n-type and bipolar organic semiconductor materials are provided. |
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