以觸媒式化學氣相沉積法製作微晶矽薄膜應用於太陽能電池之研究

Abstract

本研究中製程的儀器為觸媒化學氣相沈積法 (亦稱為熱阻絲氣相沉積法)，使用矽甲烷與氫氣製作氫化微晶矽薄膜太陽能電池。論文中首先校正並控制製程時之鎢絲溫度與基板溫度，隨後藉由改變氫氣與矽甲烷流量比率、製程壓力、鎢絲到基板間距離與不同的基板效應，探討未摻雜氫化微晶矽薄膜特性，並將其作為微晶矽薄膜太陽能電池之吸收層，探討不同特性與太陽能轉換效率之關連性。 在微晶矽薄膜中，結晶度為最重要的特性之一；本實驗中發現提升氫氣與矽甲烷流量比率、降低製程壓力、拉近鎢絲到基板間距離及使用特定基板會得到較高的結晶度，並分別探討其薄膜之電特性與鍵結組成成份。在元件的部分，基板溫度扮演相當關鍵的角色，設定較高基板溫度並拉長鎢絲預熱基板時間可有效提升元件之填充因子，使得光電轉換效率可達 2.93%。

In this study, Catalytic Chemical Vapor Deposition (Cat-CVD, also known as Hot-Wire Chemical Vapor Deposition, HWCVD) was used as the process equipment. The gases of silane (SiH4) and hydrogen (H2) were used to deposit hydrogenated microcrystalline film. In this thesis, the filament temperature and substrate temperature were calibrated at first. Then, by varying hydrogen-to-silane dilution ratio, process pressure, filament-to-substrate distance and different substrates, we have obtained the characteristics of the undoped microcrystalline silicon thin film. Also, we incorporated the undoped film into microcrystalline silicon thin film solar cell as an absorber, investigating the relationship between the thin film characteristics and device conversion efficiency. In microcrystalline silicon thin film, crystallinity is one of the most important characteristics. By conducting series of experiments, we have found that by enhancing hydrogen-to-silane dilution ratio, lowering process pressure, shortening the filament-to-substrate distance and using particular substrates would promote the crystallinity. The corresponding electrical characteristics and bonding composition were also discussed. Besides, substrate temperature played an essential role in device performance. Setting higher substrate temperature and longer pre-heating time by filament could effectively improved fill factor, making the conversion efficiency achieve 2.93%.