氮摻雜類鑽碳膜製備及其應用於太陽能電池之研究

Nitrogen-doped Diamond-Like Carbon fabrication and application to solar cells

許富珽(Fu-Ting Hsu)

指導教授 ： 徐永富 ； 王錫福

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2009年)

摘要

本研究之目的主要在於將高機械強度、高耐磨性、高化學惰性之類鑽碳(DLC)
薄膜應用於p-n接合太陽能電池中之n-type 半導體，比照a-Si:H做低成本及高耐用性非晶半導體薄膜之應用。
在本研究中以常用於工業生產用之陰極電弧沉積法沉積不含氫之類鑽碳(DLC)薄膜，並以基板施加之負偏壓控制DLC薄膜之鍵結比例，以200 V偏壓沉積之DLC薄膜可獲得最高sp3 比例77.3%，且sp3鍵比例降低時DLC膜層之導電率提升。
在沉積DLC過程中通入不同通量之氮氣做為摻雜質，可成功沉積含氮摻雜之DLC薄膜，以ESCA分析鍵結確認氮成份摻入DLC結構之中，以霍爾效應檢測確認摻雜後之DLC薄膜為n-type 半導體。以ESCA分析摻雜氮之DLC薄膜之碳氮鍵結，發現氮摻入DLC結構中與碳以N-C sp2鍵、N-C sp3鍵及N-C sp1鍵三種鍵結組態結合，碳與氮之鍵結型態主要以N-C sp2鍵、N-C sp3鍵為主，而N-C sp1鍵約只有10%，比例較低。於拉曼光譜檢測發現摻雜氮後DLC之ID/IG積分強度比值增加，分析比較無摻雜與摻雜氮DLC之鍵結比例發現摻雜後sp3鍵比例降低，氮摻入後使得DLC膜層產生些微石墨化(graphitization)現象。
摻雜後之高sp3比例與低sp3比例DLC薄膜，檢測載子濃度及導電率之變化發現均有在低氮氣通量載子濃度先提升，而後在高氮氣通量中載子濃度下降之趨勢，可能原因為在低氮氣通量下氮與碳之結合位置屬於有效摻雜者(effective doping)較多，載子濃度及導電率較高，而在高氮氣通量下氮與碳之結合位置屬於非有效摻雜者(non-doping) 較多，造成載子濃度及導電率下降，1000V-N20之摻氮DLC薄膜可獲得3x1019 cm-3之載子濃度。
將摻雜氮之DLC沉積於p-type Si基板上，並以磁控濺鍍法沉積白金電極以製成太陽能電池元件，並確認白金可與摻氮DLC薄膜及p-type Si基板形成低接觸電阻之歐姆接觸特性。於AM 1.5之模擬太陽光照條件下，較低sp3鍵比例之摻氮DLC太陽能電池元件可獲得較高之量子效率及1.05%之光電轉換效率，短路電流密度為14.5mA/cm2，開路電壓為0.2 V。

關鍵字

類鑽碳 ； 摻雜 ； 半導體 ； 太陽能電池

並列摘要

Diamond-like carbon (DLC) thin film has outstanding mechanical strength, wear resistance, and chemical inertness. The purpose of this study is to make use of these properties to enable DLC as a n-type semiconductor for solar cells. Following the example of a-Si:H, such film is applied to amorphous semiconductor with low manufacture cost and high durability.
In this study, hydrogen-free DLC thin film was prepared by well-established cathode arc deposition. The binding condition of DLC was controlled by different negative bias on the substrate. According to ESCA analysis, a more negative bias led to a decreased proportion of C-C sp3-bonds, which further enhanced the electrical conductivity of DLC film.
Selecting N2 gas as the dopant during the deposition process, nitrogen-doped DLC thin film was successfully prepared. The incorporation of nitrogen atoms into DLC structure was also verified by ESCA analysis. Tested by Hall effect, such DLC film appeared to be one n-type semiconductor. For nitrogen-doped DLC, there existed three binding possibilities between nitrogen and carbon on the ESCA spectrum, namely, N-C sp2-, N-C sp3-, and N-C sp1-bonds. In this case sp1-bonds were outnumbered by the other two categories. From Raman spectra, the relative integration intensity of two kinds of structure, i.e. ID/IG, increased as compared with un-doped DLC. The incorporation of nitrogen lowered the proportion of sp3-bonds. Moreover, slight graphitization in DLC film was observed.
After nitrogen-doped DLC was deposited on p-type Si substrate, platinum electrode was subsequently deposited thereon by magnetron sputter, so as to prepare solar cell devices. Either with nitrogen-doped DLC thin film or with p-type Si substrate, it was confirmed that Pt could form an ohmic contact, which has low contact resistance. Under one simulated sunlight illumination of AM 1.5, the lower sp3-bond proportion the nitrogen-doped DLC had, the higher quantum efficiency the corresponding device showed. A photoelectric conversion efficiency of 1.05% was calculated.

並列關鍵字

DLC ； doping ； semiconductor ； solar cell

參考文獻

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