二極式電沉積法製備氧化鎢薄膜之電致色變性質研究

Abstract

本研究以電沉積法製備氧化鎢電致色變薄膜，利用控制不同的電沉積溶液靜置時間，使鍍液產生時效作用，並將所沉積出之薄膜進行退火，最後進行電致色變特性評估。本實驗分三個部份，第一部份使用二極式電沉積系統，先求得電沉積起始電位，再決定電沉積參數，並且使用定電位法沉積氧化鎢薄膜；第二部份探討不同時效時間鍍液對於其所沉積氧化鎢薄膜的影響；第三部份將薄膜進行退火處理，並觀察退火前後對於著去色電荷進出量、著色效率與漏電流的影響。經由本實驗所量測得到的二極式電沉積起始電位為0.922 V，最佳著去色電位為2.5 V，利用1.5 V沉積電位條件沉積2分鐘所得到之薄膜厚度約為300 nm，表面粗糙度介於1.0-1.5 nm之間，退火後表面粗糙度則低於1 nm。經電致色變特性分析，沉積出最好的薄膜參數為鍍液時效4天後進行電沉積之薄膜(未退火)，其穿透率差達54.3%，光密度差為0.48，著色效率可達37.3 cm2/coul，且去色回復率為95%。經100℃退火之薄膜其著色效率與回復率均下降，分別為14.1 cm2/coul與35%，由元件電性量測證實300℃退火之薄膜具有很高的漏電流與非常狹窄的遲滯區間，因而導致薄膜難以進行著去色反應。In this study, electrodeposition method was used to fabricate WO3 electrochromic thin film. To obtain better electrochromic property of device, the solution was aged with different days before depositing process. Furthermore, some thin films were annealed to explore its effect on the electrochromic property of the device. The experiments of this study were divided into three parts. The first part was to use a two-electrode electrodepositing system to form WO3 thin film and find the start voltage of electrodeposition. The fixed voltage mode was used to fabricate the WO3 thin film. The second part was to explore the difference of the electrochromic property of thin film deposited by different ageing time. Finally, some thin films were annealed in the third part to observe the variety of properties including colored/bleached charge, coloring efficiency and current leakage difference. According to the experimental results, the starting voltage for depositing film is about 0.922 V and the best colored/bleached electric voltage is 2.5 V. The thickness of WO3 thin film is about 300 nm when the operating parameter has been controlled at 1.5 V and 2 minutes. The surface roughness of thin films before annealing is about 1~1.5 nm, and it reduced to about 1 nm after annealing process. The four days aged of solution before depositing thin film can achieve the best electrochromic properties, which makes the thin film have the transmittance difference of 54.3%, optical density difference of 0.48, and coloring efficiency of 37.3 cm2/coul and the recovery rate of 95%. The thin film annealed at 100℃ makes the devices have relatively poor color efficiency and recovery rate, about 14.1 cm2/coul and 35%, respectively. According to the electrical measurements of the films annealed at 300℃, it has been proved that the devices have higher current leakage and a narrow hysteresis region, which will make the colored and bleached of thin film is hard to develop.