硫摻雜氧化鎢奈米線之成長及應用

The Growth and Applications of Sulfur-doped Tungsten Oxide Nanowires

許祐銘

指導教授 ： 游萃蓉

國立清華大學/工學院/材料科學工程學系/碩士(2013年)

摘要

本研究藉由高溫爐管化學沉積成長一種穩定性高、無毒且對環境無害之新穎硫摻雜氧化鎢 (sulfur-doped tungsten oxide) 單晶奈米線，將此氧化物材料製作成場效電晶體以量測其電性。並且製作成感測器以及太陽能電池，了解其對於照光後之光電性，驗證其作為光感測器與太陽能電池吸收層之可行性。
本研究嘗試以調整不同重量比之反應前驅物、前驅物溫度、反應氣體氧氣與氬氣之流量比以及基板溫度，製備出不同摻雜濃度之硫摻雜氧化鎢奈米線。並以X光繞射、穿透式電子顯微鏡、能量散佈分析儀、感應耦合電漿質譜儀分析，確認已成功合成單晶之硫摻雜氧化鎢奈米線。在光學性質方面，利用紫外/可見光吸收光譜、陰極激發螢光放光系統，以及光激發螢光放光系統分析可知，隨著奈米線的硫摻雜量增加，吸收率與吸收係數也將隨之增加，其吸光係數最高可達7.8  104 cm-1，從紫外光到紅外光範圍內 (波長 300-1400 nm)，其吸光率為 83-95 %，且其具有直接與多重的能隙，並可透過硫摻雜的含量來改變能隙範圍，其主要能隙在1.7- 1.8 eV，此廣波段光譜的吸收適合作用在光電元件上。在電性量測方面，利用組裝成場效電晶體量測電性，得知該材料可為電阻，p型半導體或n型半導體。
本研究也以硫摻雜氧化鎢奈米線作為感測材料組裝成光感測器，製作出一具有高光導增益、穩定且有再現性之光感測器。此外，也嘗試將硫摻雜氧化鎢奈米線作為一新穎之氧化物吸光材料，用作太陽能電池之吸光層，並顯示出一具有p-n junction特性之理想暗電流曲線，證實其用作於光感測器及太陽能電池之未來性與可行性。

關鍵字

硫摻雜氧化鎢 ； 奈米線 ； 光感測元件 ； 太陽能電池

並列摘要

A novel, stable, and environmentally friendly optoelectronic material, W18O49(S) single crystal nanowires, was synthesized in this study in a furnace by using thermal chemical vapor deposition.
The characterization of W18O49(S) was also shown in this work. The structure, crystallinity, and the quantity of sulfur of W18O49(S) nanowires were confirmed by X-ray diffractometer (XRD), transmission electron microscope (TEM), energy-dispersive X-ray spectrometer (EDX), and inductively coupled plasma-mass spectrometry (ICP-MS), respectively. The results revealed that the single crystalline W18O49 nanowires were synthesized and sulfur was doped into the W18O49 successfully.
The results of UV-Vis spectrum, cathodoluminescence system (CL), and photoluminescence (PL) showed that the direct band gap of W18O49(S) was near 1.7 - 1.8 eV, which could be tuned by S-doping at different S-doping concentration. The W18O49(S) nanowires exhibited high absorption coefficient up to 7.8104 cm-1 and absorption rate of 83- 95 % at = 300-1400 nm which suggest that W18O49(S) of wide spectrum absorption could serve as a light absorbing agent. The electrical property of a single W18O49(S) nanowire was measured and calculated by field-effect transistor showing a p-type, n-type and resistance property.
In addition, a photo sensor and a solar cell were fabricated by W18O49(S) nanowires. The results showed a high photoconductivity gain (106-107) with good reliability and stability of photo sensor and ideal dark current curve of solar cell, which provided the feasibility of photo sensor and photovoltaic applications of the W18O49(S) nanowires presented in this study.

參考文獻

[2] BP Statistical Review of World Energy June 2011, 2011, 1-38.

[5] M. A. Green, “Third Generation Photovoltaics: Ultra-high Conversion Efficiency at Low Cost.”, Prog. Photovolt: Res. Appl., 2001, 9, 123-135.

[6] G. F. Brown and J. Wu, “Third Generation Photovoltaics.”, Laser & Photon. Rev., 2009, 3, 294-405.

[7] G. W. Crabtree and N. S. Lewis, “Solar Energy Conversion.”, Physics Today, 2007, 37-42.

[8] N. S. Lewis, “Toward Cost-Effective Solar Energy Use.”, Science, 2007, 315, 798-801.