Reorganization energies in the transports of holes and electrons in organic amines in organic electroluminescence studied by density functional theory
Reorganization energies in the transports of holes and electrons in organic amines in organic electroluminescence studied by density functional theory
复制标题
DOI：
10.1021/jp0304529
复制
发表时间：
2003-07-03
影响因子：
2.9
通讯作者：
Lao, ZPM
中科院分区：
文献类型：
--
作者：
Lin, BC;Cheng, CP;Lao, ZPM
为了设计具有良好载流子输运特性的有机电致发光器件，基于Marcus电子转移理论，对一系列化合物中空穴和电子的迁移率进行了计算研究.使用Gaussian 98程序套件中的DFT B3 LYP/6- 31 G * 方法对以下化合物进行MO计算：联苯（Bp）、4，4 '-联苯二胺（BA）、三苯胺（TPA）、三-对甲苯基胺（TTA）、4-联苯基苯基-间甲苯基胺（BPTA）、4，4'-双（苯基-间甲苯基氨基）联苯（TPD）、萘（Np）、1-萘基二苯胺（NDPA）、1-联苯基萘基苯胺（BNPA）和4，4 ′-双（1-萘基苯基氨基）联苯（NPB）。这些化合物在其中性，阳离子和阴离子状态的几何形状进行了优化。优化的几何形状，然后用于计算电离势，电子亲和势，和重组能。对于含有联苯部分的化合物（Bp、BA、BPTA、TPD、BNPA和NPB），环间距离和扭转角遵循中性大于或等于阳离子大于或等于阴离子的趋势，除了NPB，其中阴离子状态下的这两个参数大于阳离子状态下的相应参数，因为联苯部分对其LUMO的贡献很小。在TPD附近，电离势的顺序为Bp > BPTA; BNPA > BA > NPB.对于所有化合物，计算出的电子亲和势范围为-1.54至-0.05 eV，除了NPB之外，NPB由于两个萘基对LUMO的主要贡献而具有正电子亲和势0.24 eV。对于大多数化合物，空穴传输的重组能λ（+）大于电子传输的λ（-），除了NPB和BA（py）（受限的氮金字塔几何结构）。这些例外是合理的特殊结构，为他们的阴离子状态。根据lambda（+）的大小，化合物可分为两类：λ（+）大于或等于0.28 eV（BA（pl））（约束平面氮几何形状）近似于Bp > TPD近似于NPB）对于含有联苯基（具有或不具有两个氨基）且λ（+）小于或等于0.2eV的化合物（TPA近似于TTA < BPTA < BNPA近似于NDPA）。根据λ（-）的大小，化合物可分为三组：λ（-）大于或等于0.50 eV（TPD > Bp > BPTA）对于在其LUMO中具有主要联苯基的化合物，λ（-）小于或等于0.32 eV（NDPA > BNPA > Np > NPB），以及其它化合物（TPA和TTA）。根据这些结果，λ（+）主要由主要对其HOMO有贡献的部分决定，而λ（-）主要由主要对其LUMO有贡献的部分决定。因此，通过控制HOMO和LUMO的主要贡献者，并通过引入取代基来微调这些前线轨道（HOMO和LUMO）的能级，具有期望的载流子传输性质的OLED材料的系统设计应该是可行的。
To enable the design of efficient organic electroluminescence (OLED) devices with desirable charge carrier transport properties, the mobilities of hole and electron in a series of compounds were studied computationally based on the Marcus electron transfer theory. MO calculations were performed, using the DFT B3LYP/6-31G* method in the Gaussian 98 program suite, on the following compounds: biphenyl (Bp), 4,4'-biphenyldiamine (BA), triphenylamine (TPA), tri-p-tolylamine (TTA), 4-biphenylphenyl-m-tolylamine (BPTA), 4,4'-bis(phenyl-m-tolylamino)biphenyl (TPD), naphthalene (Np), 1-naphthyldiphenylamine (NDPA), 1-biphenylnaphthylphenylamine (BNPA), and 4,4'-bis(1-naphthylphenylamino)biphenyl (NPB). The geometries of these compounds in their neutral, cationic, and anionic states were optimized. The optimized geometries were then used to calculate the ionization potential, electron affinity, and reorganization energies. For compounds containing a biphenyl moiety (Bp, BA, BPTA, TPD, BNPA, and NPB), the inter-ring distance and torsional angle followed the trend neutral greater than or equal to cationic greater than or equal to anionic, except NPB in which these two parameters in anionic state were larger than the corresponding parameters in the cationic state because of a small contribution from the biphenyl moiety to its LUMO. Also, the ionization potentials follow the order Bp > BPTA; BNPA > BA > NPB approximate to TPD. The electron affinities were calculated to range from -1.54 to -0.05 eV for all compounds except NPB which has a positive electron affinity 0.24 eV due to the dominant contribution of two naphthyl groups to LUMO. For most compounds, the reorganization energy lambda(+) for the hole transport is larger than lambda(-) for the electron transport except NPB and BA(py) (constrained nitrogen pyramidal geometry). These exceptions were rationalized by the special structures for their anionic states. According to the magnitudes of lambda(+), compounds can be divided into two groups: lambda(+) greater than or equal to 0.28 eV (BA(pl) (constrained planar nitrogen geometry) approximate to Bp > TPD approximate to NPB) for compounds containing biphenyl group with or without two amino groups and lambda(+) less than or equal to 0.2 eV (TPA approximate to TTA < BPTA < BNPA approximate to NDPA) for compounds with single triarylamine group. According to the magnitudes of lambda(-), compounds can be divided into three groups: lambda(-) greater than or equal to 0.50 eV (TPD > Bp > BPTA) for compounds with a dominating biphenyl group in their LUMO, lambda(-) less than or equal to 0.32 eV (NDPA > BNPA > Np > NPB) for compounds with a dominating naphthyl group in their LUMO, and the other compounds (TPA and TTA). From these results, lambda(+) is determined mainly by the moiety which contributes predominantly to its HOMO, whereas lambda(-) is determined mainly by the moiety which contributes predominantly to its LUMO. Therefore, by controlling the major contributors to the HOMO and LUMO, and by incorporating substituents to fine-tune the energy levels of these frontier orbitals (HOMO and LUMO), a systematic design of materials for OLED with desirable charge carrier transport properties should be feasible.