Concepts of the HOMO and LUMO Traps from the Carrier Dynamics of Organic Semiconductor Isomers α-NPB and β-NPB,The Journal of Physical Chemistry C

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Concepts of the HOMO and LUMO Traps from the Carrier Dynamics of Organic Semiconductor Isomers α-NPB and β-NPB
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2020-01-22 , DOI: 10.1021/acs.jpcc.9b10234
Yuan Zhang _{1,

2} , Hu-Sheng Pang ₂ , Xue-Jun He ₁ , Hai-Tong Cai ₂ , Jie Li ₂ , Zhi-Yao Yang ₂ , Chao Tang ₂ , Shang-Hui Ye ₂ , Xi Cheng ₂ , Gong Li ₃ , Yong-Hua Li ₂ , Jun-Song Song ₁ , Wei Huang ₂

Affiliation

The carrier dynamics of two isomers, α-NPB and β-NPB, were investigated through impedance spectroscopy based on the PSO algorithm. Their structure differences are only the N atom substitution sites on the naphthalene group. For α-NPB, the N-substitution is on the α-site of naphthalene, and for β-NPB, it is on the β-site. The carrier mobility of α-NPB is much higher than that of β-NPB. But AFM morphology shows that the film of β-NPB is smoother than that of α-NPB, which is in contrast with the common idea that, for a similar molecular structure, smoother film means a larger carrier mobility. In addition, the electron mobility of α-NPB is negatively related with the electrical field, but the hole mobility of α-NPB and the electron and hole mobilities of β-NPB are all positively related with an electrical field. In a common viewpoint, the carriers should be accelerated by an electrical field since they are charged carriers. Such phenomena have to be ascribed to a trap, but only a geometric trap is not enough for that. The geometric trap should have a similar effect to both electron and hole carriers, and it also cannot explain the higher mobility of α-NPB than β-NPB. Thus, all the experimental data show that there are some new kinds of traps existing in the OSCs. Because their site in energy space is close to the HOMO and LUMO of OSCs, they are noted as HOMO and LUMO traps. With the help of HOMO and LUMO traps, the experimental data can be easy to explain.

中文翻译：

从有机半导体异构体α-NPB和β-NPB的载流子动力学看HOMO和LUMO陷阱的概念

通过基于PSO算法的阻抗谱研究了两种异构体α-NPB和β-NPB的载流子动力学。它们的结构差异仅是萘基上的N原子取代位点。对于α-NPB，N-取代在萘的α-位上，对于β-NPB，N-取代在萘的β-位上。α-NPB的载流子迁移率远高于β-NPB。但是AFM形态表明，β-NPB的膜比α-NPB的膜更光滑，这与通常的想法相反，对于相似的分子结构，更光滑的膜意味着更大的载流子迁移率。另外，α-NPB的电子迁移率与电场负相关，但是α-NPB的空穴迁移率与β-NPB的电子和空穴迁移率均与电场正相关。在一个普遍的观点中，由于载流子是带电荷的载流子，因此应通过电场来加速载流子。这种现象必须归因于陷阱，但仅几何陷阱是不够的。几何陷阱应与电子和空穴载流子具有相似的作用，并且它也不能解释α-NPB的迁移率要高于β-NPB。因此，所有实验数据表明，在OSC中存在一些新类型的陷阱。由于它们在能源空间中的位置靠近OSC的HOMO和LUMO陷阱，因此被称为HOMO和LUMO陷阱。借助HOMO和LUMO捕集阱，可以轻松解释实验数据。几何陷阱应与电子和空穴载流子具有相似的作用，并且它也不能解释α-NPB的迁移率要高于β-NPB。因此，所有实验数据表明，在OSC中存在一些新类型的陷阱。由于它们在能源空间中的位置靠近OSC的HOMO和LUMO陷阱，因此被称为HOMO和LUMO陷阱。借助HOMO和LUMO捕集阱，可以轻松解释实验数据。几何陷阱应与电子和空穴载流子具有相似的作用，并且它也不能解释α-NPB的迁移率要高于β-NPB。因此，所有实验数据表明，在OSC中存在一些新类型的陷阱。由于它们在能源空间中的位置靠近OSC的HOMO和LUMO陷阱，因此被称为HOMO和LUMO陷阱。借助HOMO和LUMO捕集阱，可以轻松解释实验数据。

更新日期：2020-01-23

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