TPD/PBD界面电致激基复合物几何结构和 电子结构的理论

利用第一性原理对由TPD⁺和PBD^-形成的电致激基复合物(TPD⁺PBD^-)进行基于密度泛函的能量、轨道等性质的计算。结果表明:界面处离子态的TPD⁺ 和 PBD^-更易形成处于更低能量状态的电致激基复合物。几何结构的数据分析表明:电致激基复合物(TPD⁺PBD^-)是电子从PBD^-转移至TPD⁺形成的电荷转移态;电致激基复合物的最低空轨道(LUMO)定域在电致激基复合物PBD^- 的一侧;它的最高占据轨道(HOMO)定域在电致激基复合物TPD⁺的一侧;且前线分子轨道无重叠。电致激基复合物的能隙为1.3 eV,与PBD 的LUMO到TPD的HOMO的能级差1.6 eV相近。在理论上说明了电致激基复合物的发光是从PBD的LUMO到TPD的HOMO的电子跃迁。

Theory on Geometrical Structure and Electronic Configuration of Electroplex at the TPD/PBD Interface in Organic Light-emitting Diodes

The studies of geometrical and electronic structure of electroplex(TPD+PBD-), which is formed by TPD+ and PBD-, were carried out by simulation calculation. The analysis of the geometrical structure data of electroplex (TPD+PBD-) suggests that the electron transfer occurs from PBD- side to TPD+ side and the electroplex between TPD+ and PBD- can be formed efficiently when the position of PBD- and TPD+ is appropriate. The electroplex (TPD+PBD-) is energetically favored comparing with isolated ions TPD+ or PBD-. This result implied that the ionic state TPD+ and PBD- at the interface TPD/PBD inside OLED tends to form electroplex. The lowest unoccupied molecular orbital (LUMO) of (TPD+PBD-) is localized at PBD- side and highest occupied molecular orbital (HOMO) of (TPD+PBD-) is localized at TPD+ side. The energy gap of electroplex (TPD+PBD-) is 1.3 eV, which is approximately equal to the energy difference of 1.6 eV between LUMO of PBD and HOMO of TPD. The emission of electroplex is theoretically intermolecular radiation transition from LUMO of PBD to HOMO of TPD.