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由于发光效率低和稳定性差,蓝色磷光材料一直是发光材料研究领域的瓶颈.为了更深层次地理解蓝色磷光分子结构与发光效率之间的关系,本工作结合密度泛函理论,运用作者新近发展的系间窜越速率的振动关联函数计算方法,定量研究了新型蓝光发射分子fac-tris(2-(4,6-difluorophenyl)pyridyl iridium(fac-Ir(F2ppy)3)的磷光光谱、辐射跃迁和无辐射跃迁速率及其与温度的依赖关系,计算结果很好地解释了实验测量结果.计算表明:(1)相较于未取代的绿光材料fac-Ir(ppy)3,杂原子F的引入增加了T1与S0的能隙,使得光谱蓝移,但没有带来额外的分子结构弛豫的重整能,从而使得该蓝色材料保持了高的发光效率;(2)无辐射跃迁过程所耗散的电子激发态能量主要是通过配体L1中的连接氟化苯环和吡啶环的C(5)—C(46)键、吡啶环内C(43)—C(44)键和C(42)—C(47)键及氟化苯环内的C(3)—C(6)键的伸缩振动,因此,理论研究表明可以通过分子设计来抑制这些振动来进一步提高这类材料的发光效率.
Due to the poor luminescence efficiency and poor stability, blue phosphorescent material has always been the bottleneck in the field of luminescent materials.In order to understand the relationship between the molecular structure of blue phosphorescent and the luminescent efficiency, this work combined with density functional theory (Fac-Ir (F2ppy) 3), a new method for calculating the vibration correlation function of the transmissibility of fac-tris (fac-tris) Transition and non-radiative transition rate and its dependence on temperature, the calculated results well explain the experimental results. The calculated results show that: (1) compared to the unsubstituted green light fac-Ir (ppy) 3, The introduction of F increases the energy gap between T1 and S0, resulting in a blue shift of the spectrum but without the additional reforming energy resulting in the relaxation of the molecular structure, thereby allowing the blue material to maintain a high luminous efficiency. (2) The energies of the electron-excited states dissipated during the transition are mainly C (5) -C (46) linking the fluorinated benzene ring and the pyridine ring in the ligand L1, C (43) -C (44) Stretching vibration of the C (42) -C (47) bond and the C (3) -C (6) bond in the fluorinated benzene ring, Here, the theory shows that these vibrations can be suppressed by molecular design to further increase the luminous efficiency of such materials.