快速大氣噴射電漿奈米孔隙氧化錫及二氧化鈦/奈米碳管之複材製程開發:應用於染料敏化太陽能電池

Abstract

本研究利用噴射式大氣電漿(Atmospheric pressure plasma jet,APPJ)進行薄膜材料快速熱退火以及奈米氧化物燒結製程。本論文內容包含兩大部分，第一部分為利用大氣噴射電漿快速熱退火多孔隙氧化錫;第二部分利用大氣噴射電漿燒結製備染料敏化太陽能電池的二氧化鈦光電極以及二氧化鈦/奈米碳管對電極，用以取代昂貴的金屬鉑(Pt)對電極，並與傳統爐管退火製程的電池作比較。 實驗一利用大氣噴射氮氣電漿燒結處理奈米多孔隙(nanoporous)氧化錫(Tin oxide,SnO2)薄膜，進行氧化錫薄膜的燒結退火製程，比起傳統爐管退火大幅降低了熱處理時間以及熱預算，達到製程上節省成本以及縮短製程時間的目的。本實驗探討大氣電漿燒結時間對多孔隙氧化錫薄膜的影響，發現隨APPJ處理時間的增加，SnO2薄膜的可見光吸收邊緣(absorption edge)先減少後增加;光學能隙先減少後增加;導電率先增加後減少;而活化能則是先減少後增加。APPJ處理時間可以用為調變SnO2材料性質的參數，合適的APPJ處理時間才會使SnO2材料適合某些用途。此處的SnO2薄膜是以網印法(Screening printing)製備，網印法搭配大氣噴射電漿製程適用於卷軸式製程(Roll-to-roll process)，且製備的多孔隙氧化錫薄膜具有高比表面積(Surface-to-volume ratio)，使其可運用於氣體感測器和化學催化劑上。 實驗二為利用大氣噴射電漿快速燒結二氧化鈦光電極和二氧化鈦/奈米碳管對電極，並研究電漿燒結處理時間對二氧化鈦/奈米碳管對電極材料性質及所組裝染料敏化太陽能電池的影響。由掃描式電子顯微鏡可發現，APPJ對二氧化鈦/奈米碳管的反應十分劇烈，APPJ燒結時間到達15秒以上時，FTO玻璃上的奈米碳管幾乎完全和電漿反應並且被移除。相較之下，經爐管退火燒結相同時間的樣本則仍且有大量的奈米碳管。由此結果可以得知奈米碳管的快速反應為熱和電漿協同作用所造成。此對電極在染秒敏化太陽能電池的應用上，最佳對電極製程參數為5秒的APPJ燒結時間，太陽能電池光電轉換效率達5.65%，和未經處理之二氧化鈦/奈米碳管對電極的光電轉換效率2.19%相比，效率提升了158%，已接近傳統鉑(Pt)對電極的太陽能電池效率6.91%但是大氣噴射電漿對於奈米碳管對電極燒結處裡的製程，製程成本較鉑對電極低廉，且製程時間相對快速，所需之熱預算較低，單位面積所需能量只約傳統爐管製程的五分之一，具有高度發展的潛力。

We used atmospheric pressure plasma jets (APPJs) for the rapid sintering of nanoporous SnO2 and CNT/TiO2. The latter was used as the counter-electrodes of dye-sensitized solar cells (DSSCs) to replace conventional precious Pt-based counter electrode. DSSCs fabricated using APPJs were compared with those made using conventional furnace calcination process. In the first part of the experiment, we sinter nanoporous tin oxide films using atmospheric pressure plasma jets (APPJs). Comparing to conventional furnace calcination process, APPJ sintering substantially reduces treatment time and thermal budget. With an increase in APPJ sintering time, the slope of optical absorption edge decreases and then increases, optical band gap decreases and then increases, the electrical conductivity increases and then decreases, and activation energy of electrical conductivity decreases and then increases. A proper APPJ sintering time is required for the sintered SnO2 to be used in certain application. The features of nanoporous SnO2 were defined by screening printing method, followed by APPJ sintering This sequential screening-printing and APPJ sintering process is applicable for roll-to-roll process. The high surface-to-volume ratio of nanoporous SnO2 make the synthesized materials useful for gas sensors or catalysts in some chemical reactions. The second part of the experiment is regarding the APPJ sintering process of CNT/TiO2 counter electrodes of DSSCs. When APPJ sintering time exceeds 15 s, the CNTs were mostly removed, indicating vigorous interaction between CNTs and N2 APPJ. In the samples sintered for the same durations by furnace-calcination process, plenty of CNTs were present This suggests that the vigorous reaction was caused by the synergetic effect of the N2 APPJ and the heat. DSSCs with CNT/TiO2 counter electrodes sintered for 5 s revealed best performance with a efficiency of 5.65%, a enhancement of 158% was achieved compared to 2.19% for the DSSC with as-deposited counter electrode. The efficiency approaches that of DSSC with sputtered Pt counter electrode. APPJ sintering reduces the fabrication thermal budget and processing time, thereby lowering the cost. The process can be scaled up as a roll-to-roll process.