Hole Transport in Triphenylamine Based OLED Devices: From Theoretical Modeling to Properties Prediction
Hole Transport in Triphenylamine Based OLED Devices: From Theoretical Modeling to Properties Prediction
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DOI：
10.1021/jp207585j
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发表时间：
2011-12-22
影响因子：
2.9
通讯作者：
Gescheidt, Georg
中科院分区：
文献类型：
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作者：
Cias, Pawel;Slugovc, Christian;Gescheidt, Georg
对一系列对位取代三苯胺类化合物，用从头算方法计算了它们的优化几何构型、HOMO和LUMO能级、电离势Ip、空穴输运λ（+）重组能和前线轨道轮廓.它们之间的关系和哈米特参数。计算结果表明，释放电子的取代基使TPA的HOMO和LUMO能量增加，而吸电子的取代基使TPA的HOMO和LUMO能量降低，这一行为反映在取代TPA的电离能的降低和升高上。计算结果表明，取代基对空穴迁移率的决定因素重组能λ（+）也有很强的影响。它的结论是适当的调谐的HOMO和LUMO水平（和，因此，电离势，IP）和重组能量（因此，空穴迁移率）的三苯胺可以通过改变TPA的电子结构，通过适当的取代。结果表明，适当调节HTM的HOMO能级，有利于降低ITO/HTL和HTL/EL界面的能垒，保证高的空穴注入率和空穴传输率。另一方面，通过适当调整LUMO能级，可以防止电子从EL泄漏到HTM层。这些计算的结果可以在设计新的HTM材料所需的性能（高效率，稳定性和耐久性）的过程中是有用的。
For the series of para-substituted triphenylamines, optimized geometries, HOMO and LUMO energy levels, ionization potentials Ip, reorganization energies for hole transport lambda(+), and frontier orbital contours have been calculated by means of ab initio computations. Relationships between them and the Hammett parameter are presented. According to calculations, electron releasing substituents increase the HOMO and LUMO energies of TPA, while electron withdrawing ones decrease it. This behavior is reflected in subsequent decreasing and increasing of ionization potentials of substituted TPAs. Calculations show that there exists also a strong substituent effect on the reorganization energy lambda(+), which is a dominating factor of hole mobility. It is concluded that proper tuning of the HOMO and LUMO levels (and, as a result, ionization potential, Ip) and reorganization energy (consequently, hole mobility) of the triphenylamine can be done by alteration of the TPA electronic structure by an appropriate substitution. It is demonstrated that the proper adjustment of the HOMO levels of HTM facilitates the reduction of an energy barrier at the interface of ITO/HTL and HTL/EL and ensure the high hole injection and hole transport rate. On the other hand, appropriate adjustment of the LUMO level prevents an electron leak from the EL into the HTM layer. Results of these calculations can be useful in the process of designing new HTM materials of desired properties (high efficiency, stability, and durability).