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Dipolar Substitution Impacts Growth and Electronic Properties of Para‐Sexiphenyl Thin Films
Advanced Materials Interfaces ( IF 5.4 ) Pub Date : 2019-12-20 , DOI: 10.1002/admi.201901707
Jiaxin Hu 1 , Nabi Aghdassi 1 , Shubham Bhagat 2 , Yves Garmshausen 3 , Rongbin Wang 1, 4 , Norbert Koch 1, 4, 5 , Stefan Hecht 3, 6, 7 , Steffen Duhm 1 , Ingo Salzmann 2, 8
Affiliation  

It is shown that fluorination of para‐sexiphenyl (6P) at the meta‐ or ortho‐positions of one terminal phenyl ring, as well as the addition of a terminal cyano‐group has an eminent impact on both growth and electronic properties of thin films. X‐ray diffraction techniques indicate that films of meta‐substituted 6P (m‐2F‐6P) develop a smooth, layered structure showing crystalline order within the layers only. Contrary, both ortho‐substituted (o‐2F‐6P) and cyano‐substituted 6P (CN‐6P) form films of 3D crystalline order. The correlation of structural information with data from ultraviolet photoelectron spectroscopy reveals that m‐2F‐6P and CN‐6P do not show preferentially oriented dipoles in the film, while o‐2F‐6P grows with collective downward orientation of the dipole moments. The subtle difference in substitution position has a dramatic impact on the thin‐film ionization energy, which increases from 5.40 (ortho) to 6.80 eV (meta) and reaches even 7.50 eV for CN‐6P. The present study shows that nonsymmetric substitution, which induces molecular dipole moments via intramolecular polar bonds, strongly impacts structure, morphology, and electronic properties of thin films. Thusly modifying common conjugated organic materials represents a valuable tool to establish smooth, crystalline layers with altered energetics at hetero‐interfaces with organic or electrode materials in electronic devices.

中文翻译:

偶极取代影响对-Sexiphenyl薄膜的生长和电子性能

结果表明,氟化-sexiphenyl(6P)的间位-或邻位的一个端子苯基环,以及通过加入封端氰基组的位上对薄膜的生长和电子性能的杰出冲击。X射线衍射技术表明,间位取代6P(m -2F-6P)薄膜会形成光滑的层状结构,仅在层内显示出结晶顺序。相反,都是邻位取代的(o‐2F‐6P)和氰基取代的6P(CN‐6P)形成3D结晶顺序的薄膜。结构信息与紫外光电子光谱数据的相关性表明,m-2F-6P和CN-6P在膜中未显示优先取向的偶极子,而o -2F-6P随偶极矩的集体向下取向而增长。取代位置的细微差别对薄膜电离能产生了巨大影响,其电离能从5.40()增加到6.80 eV(),对于CN-6P甚至达到7.50 eV。本研究表明,非对称取代通过分子内极性键诱导分子偶极矩,对薄膜的结构,形态和电子性能产生了强烈影响。因此,对普通的共轭有机材料进行改性代表了一种宝贵的工具,可以在电子设备中的有机或电极材料的异质界面上建立具有改变的能量的光滑结晶层。
更新日期:2019-12-20
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