紫精電致色變材料與元件之研究

Abstract

紫精表現出顯著的顏色對比度和有益的電致色變性能，儘管紫精以其高顏色對比度而聞名，但聚集現象而導致的循環穩定性不佳仍然存在。本論文以探討紫精的電致色變材料與電致色變元件(electrochromic device, ECD)之特性，提升其光學特性和改善長期穩定性為目的之研究。因此，本論文開發兩種新型紫精電致色變元件，並研究其電致色變性能，包括高分子離子液體(polymeric ionic liquid, PIL)和紫精衍生物。高分子離子液體以不同比例的離子液體(BMIMBF4)和高分子(POE和PVdF‒HFP)混合或合成，並通過靜電紡絲技術製備奈米纖維薄膜作為紫精電致色變元件的助電解質。另一方面，紫精衍生物(TFMBzV、DTFMBzV、TFMPV和HOPV)是選取拉電子基團(CF3)和推電子基團(OC6H13)之不同取代基合成。 首先，為了提高紫精電致色變元件的長期穩定性，並研究助電解質對電致色變性能的影響，合成新型PIL並製備奈米纖維薄膜應用於電致色變元件中。此新型PIL以高分子PVdF‒HFP作為主鏈，在其主鏈上接枝BMIMBF4，使其對紫精離子之間產生分子相互作用，進而顯著減少衰退以實現長期穩定性。其次，為了研究紫精兩側之取代基對其電化學性質和光學性質的影響，選取兩個極端的取代基，即拉電子基團和推電子基團進行研究。在本論文的研究和討論中，成功地提出一個使用PFI‒BF4_1.5薄膜作為半固態電解質的PV/Fc ECD經過10,000圈和50,000圈循環操作後分別具有95.9%和88.3%的保留率，並且具有77.8%的ΔT和371.9 cm2 C‒1的ηe。此外，TFMPV/Fc ECD具有 77.8%的ΔT和371.9 cm2 C‒1的ηe，且通過PFI‒BF4_1薄膜作為半固態電解質引入TFMPV/Fc ECD中，其在10,000圈循環操作後保留率達到97.8%。在許多文獻當中，很少能做到50,000圈以上的循環操作後還能維持極高的穩定性(>80%)，並同時有高的光學對比度(>70%)。

Since the viologen itself demonstrate significant color contrast and beneficial electrochromic performance. Even though the viologens were well‒known for their high color contrast, their lack of cycling stability resulting from aggregation or aging process remains. In this dissertation, viologen‒based electrochromic devices (ECDs) were studied for the enhancement of optical properties and improvement of long‒term stability. Therefore, the electrochromic (EC) performance of two novel viologen‒based ECDs, including polymeric ionic liquid (PIL) and viologen derivatives, was investigated. The PIL was utilized through different ratios of the ionic liquid (BMIMBF4) and the polymer (POE and PVdF‒HFP) to form a nanofiber membrane by the electrospinning and be a supporting electrolyte in the viologen‒based ECDs. The viologen derivatives (TFMBzV, DTFMBzV, TFMPV, and HOPV) were synthesized with different substituents like the electron‒withdrawing group (CF3) and the electron‒donating group (OC6H13). Firstly, to improve the long‒term stability of the viologen‒based ECDs, and study the influence of the electrolyte on EC performance, a novel PIL was synthesized and formed a nanofiber membrane to utilize in an ECD. The novel PIL, using polymeric PVdF‒HFP as the main chain, was grafted with BMIMBF4 on the main chain to arouse the molecular interaction with the viologen ions, thereby significantly reducing recession for long‒term stability. Secondly, to study the influence of the substituent on both sides of viologen for its electrochemical properties and optical properties, thus, chosen two extreme substituents, an electron‒withdrawing group, and an electron‒donating group, were investigated. In the research and discussion in this thesis, we have successfully proposed the PV/Fc ECD with PFI‒BF4_1.5 membrane performs high retention of 95.9% and 88.3% after 10,000 and 50,000 cycles, respectively, and exhibits a 77.8% of ΔT and 371.9 cm2 C‒1 of ηe. In Addition, the proposed TFMPV/Fc ECD performed a high ΔT of 77.8% and a high ηe of 371.9 cm2 C‒1, and the retention was achieved at 97.8% after 10,000 cycles by the improvement of the PFI‒BF4_1 introduced in the ECD. It is noteworthy that few literatures achieve such high stability (>80%) after more than 50,000 cycles, while maintaining high optical contrast (>70%) simultaneously.