Theoretical Investigations Into The Electron And Ambipolar Transport Properties Of Anthracene-Based Derivatives

Organic semiconductor materials exhibit many desirable properties,such as low cost,ease of processing and synthesis,and good flexibility.Therefore,as active layer materials,they have been rapidly and widely applied to organic light emitting diodes,organic field effect transistors,organic light emitting diodes,organic semiconductor sensors,and organic photovoltaic cells.The performance of these electronic devices is primarily determined by the charge transport properties of organic semiconductor materials.Therefore,organic semiconductor materials with large carrier mobility have always been the goal of researchers.The acene-based molecules are widely studied due to the linear extension of the?-conjugated framework,which could enhance the intermolecular?-orbital overlap in the solid state and lead to efficient charge carrier transport,exhibiting high mobility.Among them,the triphenylene molecule,anthracene,which is the best solubility,easy processing and good stability,has a widely used and studied in recent years,such as triisopropylsilylethynylanthracene derivatives.2-?4-hexylphenylvinyl?anthracene,2,6-diphenylanthracene,and so on.However,these studies mainly performed hole transport behavior,electron or bipolar charge transport materials with anthracene as a skeleton are still scarce.First of all,for electron transport materials,it is required that the derivative of anthracene has good air stability and industrial operation stability,which is a difficult point to achieve;for bipolar materials,it is required not only that the material has holes and electron at the same time.And balance of hole and electron transport capabilities are also required.In order to obtain an anthracene derivative having electron or ambipolar transport behavior,two series of mercapto derivatives modified with trifluoromethyl groups?-CF₃?and cyano groups?-CN?at the 9,10 positions of the anthracene core were studied.Their electronic structure and crystal packing were also analyzed and compared.Based on the incoherent charge hoping model,the charge carrier mobilities are evaluated by quantum nuclear tunnel theory.The calculation results show that the-CN substituted anthracene derivative has a lower LUMO orbital energy level?0.45⁰.55 eV?than the-CF₃ substituted at 9,10-position derivative of the same structure,which is more conducive to electron transporting for the commonly used Au electrode.At the same time,the-CN substituted anthracene derivatives have larger EAs,which means better stability,but because of the suitable degree of frontier orbital energy level that-CF₃ can be reduced,it can be used as an excellent groups for regulating the injection of bipolar materials.For the two parameters related to the charge transfer rate:recombination energy and transfer integral,the-CN substituted anthracene derivatives have smaller recombination energies than that of the-CF₃ at the 9,10-position of anthracene due to the non-bonding effect of–CN.Because of the steric hindrance and F…H,the-CF₃groups will destroy the plane rigidity of the anthracene,causing distortion and making-CF₃ derivatives have large recombination energy.For the transfer integral,the-CN substituted anthracene derivative is easier to have a smaller slip distance and easier formed tightly packed,hence causing large electronic coupling.For the molecules we studied,the molecules of Series 1 substituted by-CF₃ and the molecules of Series 2 substituted by-CN have the potential to become bipolar charge transport materials and n-type charge transport materials,respectively.The molecule1-B in Series 1 containing-CF₃ groups is an ambipolar organic semiconductor?OSC?material with 2D transport network,and its value of?h-max/?e-max is 1.75/0.47cm² V^-1 s^-1 along different directions;2-A and 2-C in Series 2 with-CN groups are excellent n-type OSC candidates with the maximum intrinsic mobilities of 3.74 and2.69 cm² V¹ s^-1 along?-?stacking direction,respectively.Besides,the Hirshfeld surface and QTAIM analyses were applied to reveal the relationship between noncovalent interactions and crystal stacking.