Debata Suryakanti, Sahoo Smruti R, Khatua Rudranarayan, Sahu Sridhar
High Performance Computing lab, Department of Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad, India.
Phys Chem Chem Phys. 2021 Jun 2;23(21):12329-12339. doi: 10.1039/d1cp00008j.
In this study, we present an effective molecular design strategy to develop the n-type charge transport characteristics in organic semiconductors, using ring-fused double perylene diimides (DPDIs) as the model compounds. These dimeric-PDIs are formed by joining two separate PDI-units along their bay positions through ring fusion with pyrene, coronene and their N-doped counterparts. The bridging type has a significant steric effect at the annulation positions and controls the molecular geometry, mostly imposing buckling in the structure. The crystal structures of the designed compounds are also theoretically predicted. Thereafter, electronic structure parameters, molecular packing motifs, charge coupling strength and anisotropic mobilities were investigated to understand the charge transport efficiency of these systems. Among all the studied molecules, the 4N-coronene-fused DPDI (DPDI-6) is found to possess a lower LUMO level and a high EA, suggesting air-stable electron injection. Besides, DPDI-6 shows strong intermolecular electron coupling and possesses high electron mobility (μe = 5.31 × 10-2 cm2 V-1 s-1), which is better as compared with the other DPDI-compounds reported here. The DPDIs also possess optical absorption in the UV-visible region, opening up possible applications in organic photovoltaics. Besides, from the non-linear optical (NLO) analysis, DPDI-3 is found to possess the highest first-order hyperpolarizability, which is even better as compared with the reference compound urea, making it a promising candidate for NLO applications.
在本研究中，我们提出了一种有效的分子设计策略，以利用稠环双苝二酰亚胺（DPDIs）作为模型化合物来开发有机半导体中的n型电荷传输特性。这些二聚体苝二酰亚胺是通过芘、蒄及其氮掺杂类似物与两个单独的苝二酰亚胺单元沿其湾区位置进行环稠合而形成的。桥连类型在环合位置具有显著的空间效应，并控制分子几何形状，大多使结构产生弯曲。还从理论上预测了所设计化合物的晶体结构。此后，研究了电子结构参数、分子堆积模式、电荷耦合强度和各向异性迁移率，以了解这些体系的电荷传输效率。在所有研究的分子中，发现4N-蒄稠合的DPDI（DPDI-6）具有较低的最低未占分子轨道（LUMO）能级和较高的电子亲和势（EA），表明其具有空气稳定的电子注入能力。此外，DPDI-6表现出强的分子间电子耦合，并具有高的电子迁移率（μe = 5.31×10-2 cm2 V-1 s-1），与本文报道的其他DPDI化合物相比更好。DPDIs在紫外-可见区域也具有光吸收，这为有机光伏领域开辟了可能的应用。此外，通过非线性光学（NLO）分析，发现DPDI-3具有最高的一阶超极化率，与参考化合物尿素相比甚至更好，使其成为NLO应用的有前途的候选物。
