氮氣大氣噴射電漿還原鉑-氧化鋅及鉑-氧化錫對電極染料敏化太陽能電池

Abstract

本研究分兩部分，分別為以氮氣大氣噴射電漿還原鉑鋅氧化物及鉑錫氧化物，並用於染料敏化太陽能電池(DSSC, dye-sensitized solar cell)之對電極。第一部分為混合等體積比例之氯鉑酸及醋酸鋅之前驅物溶液以旋轉塗佈的方式塗佈於氟摻雜氧化錫(FTO, fluorine-doped tin oxide) 之導電玻璃，再利用氮氣大氣噴射電漿進行還原製程，大氣電漿之溫度控制在510 °C，且透過調控電漿時間參數以獲得最佳催化效果之參數。第二部分為混合等體積比例之氯鉑酸及氯化亞錫之前驅物溶液以相同之製程塗佈於FTO導電玻璃，同樣利用氮氣大氣噴射電漿進行還原製程，將大氣電漿之溫度控制在510 °C，且透過調控電漿時間參數以獲得最佳催化效果。藉由掃描式電子顯微鏡可觀察出鉑鋅氧化物奈米粒子以及鉑錫氧化物奈米粒子皆均勻散佈於FTO導電膜上，可做為觸媒粒子給予染料敏化太陽能電池電解液中所需要的I-及I3-之氧化還原反應，並藉由X射線光電子能譜儀(X-ray photoelectron spectroscopy, XPS)進一步分析其化學組成。大氣電漿處理後還原鉑為金屬態，而鋅及錫以氧化態存在。而透過阻抗分析、Tafel 曲線量測以及元件效率測試可歸納出最佳之電漿參數為處理60秒之鉑鋅氧化物對電極，而鉑錫氧化物之對電極也以相同之分析方法歸納出最佳電漿參數為120秒，且上述之分析顯示一致的結果，催化效果越好具有較低的電荷傳輸電阻(charge transfer resistance)以及較高的交換電流密度(exchange current density)，而在太陽能元件特性上也具有較高的填充因子以及太陽能電池效率。

We use atmospheric-pressure plasma jet (APPJ) to fabricate Pt-ZnOx and Pt-SnOx as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). Regarding Pt-ZnOx, we first mix the same volume of chloroplatinic acid and zinc acetate solutions. The mixture is spin-coated on FTO glass substrates, followed by calcination using nitrogen APPJ. Due to the synergetic effect of plasma and heat, the reduction process can be completed in a few seconds. The APPJ processing time is optimized to improve the catalytic activities of Pt-ZnOx CEs. Regarding Pt-SnOx,we mix the same volume of chloroplatinic acid and tin chloridesolutions. Rest of the procedures are the same as those mentioned above. The maxmum temperature is ~510°C in both cases. The surface morphology was investigated by scanning electron microscope (SEM).Both Pt-ZnOx and Pt-SnOx nanoparticles are well-distributed on the FTO substrates. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analyses imply that Pt is in metallic form whereas Zn and Sn are still in oxidation states after APPJ calcination. Electrochemical impedance spectroscopy (EIS) and Tafel experiments show that Pt-ZnOx and Pt-SnOx CEs exhibit low charge transfer resistance and high exchange current density for DSSCs of better performance. This also indicates that Pt-ZnOx and Pt-SnOx CEs have good catalytic ability to for redox reaction between I3- and I-.