Tunable Optoelectronic Properties of Polydimethylsiloxane-Arylazopyrazole Flexible Composite
Tunable Optoelectronic Properties of Polydimethylsiloxane-Arylazopyrazole Flexible Composite
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DOI：
10.1109/southeastcon45413.2021.9401853
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发表时间：
2021-03
期刊：
影响因子：
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通讯作者：
I. Uba;K. Ghebreyessus;D. Geddis;U. Hommerich
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文献类型：
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作者：
I. Uba;K. Ghebreyessus;D. Geddis;U. Hommerich
对柔性电子平台日益增长的兴趣促使将客体结构引入聚合物材料中，以获得具有新颖光学和电子特性的复合材料。在这项工作中，通过在聚二甲基硅氧烷基质中掺入芳基偶氮吡唑（AAP）的新型衍生物，实现了光电复合材料。通过光谱法研究了 365 nm 紫外光源照射前后的复合材料。紫外-可见光区域的响应揭示了嵌入 AAP 的存在和光致异构化对特性的显着调节，以及对浓度的强烈依赖性。原始状态下折射率为1.83 - 2.38，紫外线照射后折射率为1.59 - 1.71；相关介电常数分别为 3.5 - 5.5 和 3.0 - 4.0。随着 AAP 浓度的增加，浓度的影响表现为性能的增加。在原始状态下，复合材料吸收光谱显示最大值集中在 340 nm，这是 AAP 中典型的 $\pi \rightarrow \pi^{*}$ 转变。暴露于紫外线后，由于 AAP 向顺式结构的共形变化，由于 $\mathrm{n}\rightarrow\pi^{*}$ 转变，最大值移动到 $\sim 310$ nm，次峰出现在 450 nm。吸收光谱分析表明，二次 $\mathrm{n}\rightarrow\pi^{*}$ 跃迁是间接的，并且由于光异构化过程中 AAP 分子的旋转而由声子辅助，而初级 $\pi\rightarrow\pi^{*}$ 激发是直接的，间隙值为 3.1-3.5 eV。
Growing interest in flexible electronic platforms spurs introduction of guest structures into polymeric materials to achieve composites with novel optical and electronic properties. In this work, optoelectronic composites were realized by incorporation of novel derivative of arylazopyrazole (AAP) in polydimethylsiloxane matrix. The composites were investigated before and after irradiation with 365 nm UV source through optical spectroscopy. The responses at UV - Vis region, revealed significant regulation of properties by the presence and photoisomerization of embedded AAP, as well as a strong dependence on concentration. The refractive indices ranged from 1.83 - 2.38 in pristine state and 1.59 - 1.71 upon UV irradiation; and associated dielectric constants were 3.5 - 5.5 and 3.0 - 4.0, respectively. The impact of concentration manifested in increasing magnitude of properties as AAP concentration increased. In pristine state, composites absorbance spectra showed maxima centered at 340 nm that was typical of $\pi \rightarrow \pi^{*}$ transition in the AAP. After exposure to UV, the maxima shifted to $\sim 310$ nm with secondary peak occurring at 450 nm due to $\mathrm{n}\rightarrow\pi^{*}$ transition because of conformal change of the AAP to cis structure. Analyses of absorbance spectra showed that the secondary $\mathrm{n}\rightarrow\pi^{*}$ transition was indirect and assisted by phonons due to rotation of AAP molecules during photo-isomerization, while primary $\pi\rightarrow\pi^{*}$ excitation was direct with gap values 3.1- 3.5 eV.