| 摘要: | 本論文聚焦於熱致型近晶A相(Smectic A，簡稱SmA)液晶與染料敏化太陽能電池(Dye-sensitized solar cell，簡稱DSSC)結合應用於智慧窗的實驗研究，探討不同摻雜組成對液晶排列、光學特性與電場響應特性的影響，以8CB為主體液晶，其在室溫(約22.5-34.5°C)下呈現SmA相，並依序摻入手性分子R5011與離子鹽LiClO4，並於基板作DSSC之處理，檢視其同時作為熱控型智慧窗與太陽能電池的潛力。於第一部分之實驗顯示，在無基板配向的液晶盒中，純8CB液晶在室溫SmA相下自然形成雙穩態排列，其中包含垂直排列之透明區與多區域層狀結構之散射區，透過偏光顯微鏡觀察，該區域散射之來源為SmA層列結構的層間錯位及導軸偏轉。此雙穩態結構具一定程度記憶特性，約於34.5°C發生SmA相相變至相列相(N)的過程，並於42°C以上轉為各向同性態；當加入1 wt%手性分子R5011後，該液晶於向列相時(34.5-42°C)轉為膽固醇相(N*)，並於膽固醇相中形成焦錐態散射結構，而在近晶相中因層列結構與螺旋扭力之競爭，保留部分垂直排列，使得在溫度變化下，該液晶盒具備近晶相之選擇性透光與膽固醇相散射之行為；進一步摻入1.5 wt% LiClO4離子鹽後，液晶在室溫(約22.5-32˚C)之SmA*相中呈現全域均勻垂直排列之穿透態，顯著提升透明度，此效應推測源於疏水性ClO4-離子與8CB分子–CN偶極之間的吸附作用，使離子鹽提供額外之垂直錨定力造成。並且透過外加不同頻率之電場，可實現液晶盒於低溫(約22.5-32˚C)透明轉為散射；高溫(約32-42˚C)散射轉為透明態之電致切換，此液晶盒具備兩種調控特性(溫控與電控)，適合用於主動式智慧窗設計；於第二部分實驗將此液晶混合物注入經DSSC製程之基板液晶盒(樣品採TiO2/染料N719及TiO2/染料N719+JK-5作為陽極，Pt作為陰極)，仍保有第一部分實驗之光閥行為，同時系統具備基礎光電輸出能力，並且摻雜之離子鹽貢獻垂直配向力的同時也提供作為DSSC使電子氧化還原之可能，於本實驗中，該DSSC液晶盒之開路電壓可達約0.51 V，但短路電流僅達3.77 μA。雖因TiO2薄膜厚度與將電解液材料替換為高阻值液晶混合物之限制，整體轉換效率偏低，但已驗證其可行性。本論文實驗結果證實，離子在近晶相液晶中可提供穩定可調的配向力，配合手性分子作為合適的智慧窗光閥，並與DSSC結構整合，發展具雙重功能之新型液晶裝置。;This thesis focuses on the experimental investigations of integrating thermotropic smectic A (SmA) liquid crystals (LCs) with dye-sensitized solar cells (DSSCs) for smart window applications. The study explores how different doping compositions influence LC alignment, optical properties, and electric field responsiveness. The base SmA LC used herein is 8CB, which exhibits a SmA phase at room temperature. It is sequentially doped with a chiral dopant (R5011) and an ionic salt (LiClO4), and subsequently processed on DSSC-treated substrates to examine its potential as both a smart light valve and a photovoltaic device. In the first part of the thesis, it was observed that pure 8CB, injected in LC cells without any alignment layers, spontaneously forms a bistable texture at room-temperature SmA phase. This consists of vertically aligned transparent regions and multi-domain layered scattering regions. The observations under a polarized optical microscopy reveal that the scattering arises from layer misalignment and director tilting within the SmA structures. This bistable state exhibits partial memory behavior, transitioning to the nematic (N) phase at approximately 34.5°C and to the isotropic phase above 42°C. When 1 wt% of the chiral dopant R5011 is doped into the above system, the LC transforms into a cholesteric (N*) phase within the nematic temperature range (34.5–42°C), forming focal conic scattering textures. In the SmA* phase, the competition between the helical twisting force and smectic layer ordering retains partial vertical alignment, leading to selective light transmission in the smectic phase and scattering behavior in the cholesteric phase under thermal modulation. Further doping with 1.5 wt% LiClO4 results in a uniformly homeotropic (vertically aligned) transparent state in the SmA* phase at ~22.5–32°C, significantly enhancing optical clarity. This effect is attributed to induced adsorption of hydrophobic ClO4- ions onto the –CN dipoles of 8CB, providing additional vertical anchoring force. Upon applying electric fields of varying frequencies, the LC device exhibits dual-mode electro-optic switching: a transition from transparent to scattering at low temperature (~22.5–32°C), and from scattering to transparent at higher temperature (~32–42°C). These findings demonstrate that the LC device possesses both thermal and electric control over light modulation, making it suitable for active smart window applications. In the second part of the study, the LC mixture was filled into LC cells fabricated with DSSC treatment (using TiO2/N719 and TiO2/N719+JK-5 as photoanodes, and Pt as the counter electrode). The devices retain the light-valve behavior observed in the first part while also exhibiting basic photovoltaic functionality. The doped ionic salt not only contributes to vertical alignment but also plays a role in facilitating redox reactions in the DSSC. The fabricated LC–DSSC hybrid cells achieve an open-circuit voltage of approximately 0.51 V and a short-circuit current of 3.77 μA. Although the overall power conversion efficiency is limited due to the thin TiO2 layer and the replacement of liquid electrolyte with a high-resistivity LC mixture, the results validate the feasibility of the integrated system. Overall, this work confirms that ionic doping in smectic LCs provides a stable and tunable alignment mechanism. Combined with appropriate chiral dopants, the system functions as a smart window. Moreover, integration with DSSC structures enables the development of multifunctional LC devices with dual optical and energy-harvesting capabilities. |
