本論文旨在探討摻雜二色性螢光材料對向列型液晶光電特性的影響，研究內容主要分為兩個部分。第一部分著重於探討螢光分子本身對液晶電光行為的影響。摻雜具有π電子共軛結構的二色性螢光分子於液晶中，其液晶之臨界電壓與飽和電壓的變化可由穿透率-電壓曲線中得知，在未照射激發光下，低濃度的二色性螢光材料的摻雜不影響臨界電壓值，但會些微使飽和電壓提高。此外，於激發螢光材料時量測其液晶之穿透率-電壓曲線也可觀察到螢光材料受激發與否亦不影響液晶之臨界電壓，但飽和電壓會些微降低，可推論因光導效應影響了電場於液晶內的分布。第二部分則液晶對二色性螢光材料螢光光學特性的影響，評估當二色性螢光分子摻雜於水平配向向列型液晶中，是否因液晶分子的有序排列與限制導致原本非偏振的螢光轉變為具有偏振性的發光行為。透過量測不同偏振方向的螢光強度，並計算其偏振度，以定量分析螢光偏振特性。同時，本研究亦進一步探討外加電場對螢光強度的影響，藉由量測穿透率-電壓曲線，確定液晶樣品的飽和電壓，並比較電場施加前後螢光強度的變化，進一步分析電場驅動下液晶分子重新取向對螢光性質的調控能力。綜合上述，本研究展示二色性螢光材料在有序排列的液晶中不僅影響螢光偏振態與強度，對未來發展具光致發光偏振控制功能之液晶光電元件具有參考價值。;This thesis investigates the effects of doping dichroic fluorescent materials into nematic liquid crystals (NCLs) on their electro-optical properties. The research is divided into two main parts. The first part focuses on how the dichroic fluorescent molecules influence the electro-optical behavior of the host NLCs. The threshold and saturation voltages of the NLCs doped with dichroic fluorescent molecules were determined from their voltage–transmittance (T–V) curves. The results show that the threshold voltage remains unaffected by the doping, whereas the saturation voltage exhibits a slight shift toward higher voltages. In addition, T–V curves were also measured under photoexcitation of the fluorescent materials. It was observed that the excitation state of the doped fluorescent molecules does not alter the threshold voltage, but slightly reduces the saturation voltage. It can be inferred that the photoconductive effect influences the distribution of the electric field within the LC medium. The second part of this research investigates how the homogeneous alignment of NLCs influences the fluorescence behavior of the embedded dichroic fluorescent molecules. Specifically, it examines whether the originally unpolarized fluorescence becomes polarized due to the anisotropic alignment and spatial constraints imposed by the NLC orientation. By measuring the fluorescence intensities with different polarization directions and calculating the degree of linear polarization, the polarization characteristics of the emitted fluorescence are quantitatively analyzed. Furthermore, the influence of an external electric field on fluorescence intensity has also been investigated. Through the measurement of the T–V curve, the operating voltage of the dichroic fluorescent material-doped NLCs can be determined. The changes in fluorescence intensity with and without the applied electric fields are then compared to evaluate the modulation of fluorescence induced by the electric-field-driven realignment of NLCs. In summary, this study demonstrates that incorporating dichroic fluorescent materials into NLCs with ordered orientations can effectively modulate fluorescence polarization and intensity. These findings provide valuable insights for the future development of LC-based optoelectronic devices with controllable photoluminescence polarization characteristics.
