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標題: | 矽奈米線陣列的形貌與光電特性及其在有機無機混成太陽能電池之應用 Morphology and Optoelectronic Properties of Silicon Nanowire Arrays and Its Application on Organic/Inorganic Hybrid Solar Cells |
作者: | Hong-Jhang Syu 許紘彰 |
指導教授: | 林清富(Ching-Fuh Lin) |
關鍵字: | 矽奈米線,矽奈米結構,混成太陽能電池,PEDOT:PSS,有機半導體, silicon nanowires,silicon nanostructures,hybrid solar cells,PEDOT:PSS,organic semiconductors, |
出版年 : | 2013 |
學位: | 碩士 |
摘要: | 本論文中,我們將探討矽奈米線陣列的製備方法對其形貌、光學、電學特性,以及應用在有機/無機混成太陽能電池上的影響。在矽奈米線陣列的製備上,我們使用金屬輔助化學蝕刻法(MacEtch),著眼於MacEtch的常溫、常壓、低耗時的特性符合環境保護的要求。MacEtch有兩種,其一是在蝕刻前(before etching)將輔助蝕刻用的金屬預先用電子槍蒸鍍機鍍在矽晶圓上,此法稱作BE法,金屬通常為銀。其二,與BE法相反,金屬在鍍上矽晶圓的過程中,同步誘發氫氟酸蝕刻矽晶圓,又稱作DE法,常用金屬與BE法相同。研究結果指出,BE法所得的矽奈米線陣列有較均勻且緊密的分佈,DE法的結果則相反,而且,DE法的矽奈米線在高度超過1微米後有嚴重聚集成束的現象。光學表現方面,在相似長度時,BE法的奈米線陣列有較高的反射率,除了在500奈米以下的波段,此波段的1微米長度以下的DE法奈米線反而有較高的反射率。電特性上,奈米線長度越長少數載子生命其越短。在相似長度下,BE法矽奈米線陣列的少數載子生命期較低。以上所述之形貌、光學、電學特性和製備過程的關係將在第三及第四章詳述。
在有機/無機混成太陽能電池的應用上,我們使用一有機導體poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)與矽奈米線搭配。與無機太陽能電池不同的是,PEDOT:PSS在此作電子阻擋及電洞傳遞之用,因其最低未填滿軌域(LUMO)及最高已填滿軌域(HOMO)分別為-3.5及-5.0電子伏特,此兩者分別高於矽的傳導帶-4.05電子伏特及價電帶-5.17電子伏特。換句話說,PEDOT:PSS是用來規範矽產生的電子及電洞運動方向。根據結果所示,奈米線長度越短,元件表現越好;相似長度下,奈米線密度低者,表現也較佳。承前段所述,此乃因長度越長,少數載子生命其較低,且密度越高,PEDOT:PSS水溶液越不容易滲入奈米線間的空隙所致。所以,DE法的0.464奈米長之矽奈米線混成太陽能電池的表現最佳,短路電流密度(Jsc)是28.55 毫安培/平方公分,開路電壓(Voc)是0.524伏特,功率轉換效率(PCE)是9.56%。 In this thesis, we investigate the influence of preparation method on morphology, optical, and electrical properties of silicon nanowire (SiNW) arrays, and their applications on organic/inorganic hybrid solar cells. The SiNW arrays are obtained by metal-assisted chemical etching (MacEtch) processes because MacEtch can process in normal temperature and pressure, and the operation time is short. Those characteristics are ecological. MacEtch has two types of working method. One is depositing assisted metal, for example, Ag, by an electron gun (e-gun) evaporator before etching (BE). The other is depositing assisted Ag during the etching (DE) process. The results reveal that BE-method MacEtch can produce more uniform and denser SiNW arrays than DE-method ones. In terms of optical properties, BE-method SiNW arrays have higher reflectance than DE-method ones, except the wire length less than 1 μm in the wavelength range less than 500 nm. Regarding the electrical property, longer SiNW arrays have shorter minority-carrier lifetime. Moreover, in the condition of similar wire length, BE-method SiNW arrays have shorter minority-carrier lifetime than DE-method ones. The relation of morphology, optical, and electrical properties and preparation method will be discussed detailed in chapter 3 and 4. In terms of the application of SiNWs on hybrid solar cells, a conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is combined with both BE- and DE-method SiNW arrays to form hybrid solar cells. Unlike inorganic solar cells, PEDOT:PSS is functioned as electron blocking layer and hole transport layer. It is because the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) of PEDOT:PSS are -3.5 eV and -5.0 eV. Both of them are higher than conduction band (-4.05 eV) and valence band (-5.17 eV) of Si, respectively. On the other hand, PEDOT:PSS regulate charge transport here. The results reveal that short-SiNW device has better performance, and, in the condition of similar wire length, sparse-SiNW device also has better performance. It is because long SiNW has short minority-carrier lifetime, and dense SiNWs hard to make PEDOT:PSS solution infiltrate into wire gaps. Therefore, the best cell performance happens on the DE-method SiNW/organic hybrid solar cell with wire length of 0.464 μm. The short-circuit current density (Jsc) is 28.55 mA/cm2, open-circuit voltage (Voc) is 0.524 V, and power conversion efficiency (PCE) is 9.56%. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/17114 |
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