【摘要】 利用第一性原理,详细研究了三种三嗪基热活化延迟荧光分子的激发态性质.采用最优化的哈特利-福克方法,计算了第一单重激发态和第一三重激发态之间的能差.通过对自然跃迁轨道,电子空穴分布以及电子空穴重叠度的分析,发现三个分子的第一单重激发态都含有电荷转移和局域激发的成分.通过引入因子△r和电子-空穴交叠积分S,定量地分析了分子的激发态属性.研究发现对称的分子结构能够使得前线轨道分布更加的离域,使得单重态和三重态能差较小,且是实现热活化延迟荧光的一个重要条件.此外在供体和受体之间插入苯环能够增加振子强度,提高发光效率.最后采用最优化哈特利-福克方法计算的能态结构,这为研究激发态的动力学过程提供指导与帮助.更多还原

【Abstract】 Three kinds of triazine based organic molecules designed for thermally activated delayed fluorescence(TADF) emitters are investigated by first-principles calculations.An optimal Hartree-Fork(HF) method is adopted for the calculation of energy gap between the first singlet state(S1) and the first triplet state(T1).The natural transition orbital,the electronhole(e-h) distribution and the e-h overlap diagram indicate that the S1 states for the three systems include both charge-transfer and some localized excitation component.Further quantitative analysis of the excitation property is performed by introducing the index Ar and the integral of e-h overlap S.It is found that symmetric geometry is a necessary condition for TADF emitters,which can provide more delocalized transition orbitals and consequently a small Sl-T1 energy gap.Artful inserting aromatic groups between donors and acceptors can significantly enhance the oscillator strength.Finally,the energy state structures calculated with the optimal HF method is presented,which can provide basis for the study of the dynamics of excited states.更多还原