研究生: |
黃厚穎 Hou-ying Huang |
---|---|
論文名稱: |
含矽太陽電池之研究 Study of Silicon-Based Solar Cell |
指導教授: |
莊敏宏
Miin-horng Juang |
口試委員: |
葉文昌
Wen-chang Yeh 劉政光 Cheng-kuang Liu |
學位類別: |
碩士 Master |
系所名稱: |
電資學院 - 電子工程系 Department of Electronic and Computer Engineering |
論文出版年: | 2006 |
畢業學年度: | 94 |
語文別: | 英文 |
論文頁數: | 113 |
中文關鍵詞: | 太陽電池 、能帶穿遂 、碳化矽 、矽鍺 |
外文關鍵詞: | solar cell, band to band tunneling, silicon carbine, silicon germanium |
相關次數: | 點閱:348 下載:1 |
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由於石油將於本世紀內用磬,尋找新的替代能源已是當務之急。太陽能乾淨且幾乎無限,所以許多科學家都在努力研發高效率低成本太陽電池。目前太陽電池多為單晶矽或多晶矽之p-n接面,這種傳統結構之轉換較率已逼近理論上限。因此在本論文中,我們將探討過去提高矽太陽電池效率的手段,使用這些方法在MEDICI中模擬出傳統結構多晶矽太陽電池,藉此找出電池各部分對效率的影響,嘗試將傳統結構矽太陽電池最佳化。
除此之外,我們也試驗了新結構電池。這種新結構利用了能帶穿遂效應(Band to band tunneling)來產生額外的載子,我們發現穿遂產生的載子甚至比光激發的載子更多。雖然這種結構因為載子多而有較高的短路電流,但是由於高電流區的輸出電壓太低,導致它的效率仍然比不上傳統電池。我們也在它通道上方加了一個閘極,閘極電壓會稍稍改變通道區的能帶,也會對能帶穿遂效應有影響。為了更進一步增強它內部的穿遂效應,我們使用能帶較低的矽鍺合金(SiGe)來取代矽。一如預料,矽鍺穿遂電池有更明顯的穿遂效應,所以它擁有更高的短路電流。雖然如此,由於它的能帶小,開路電壓較矽穿遂電池更大,因此效率比不上矽穿遂電池,遑論傳統結構。對於穿遂電池,我們將會討論摻雜濃度、莫耳分率(mole fraction)、淺接面以及閘極電壓的影響。
最後,我們模擬了水平結構的電池。這種結構雖無助於提升效率,但是卻方便和IC製程整合,同時也方便製成串聯電路來提高輸出電壓。對於這種結構,我們也對它測試了通道長度、電池厚度以及淺接面對效率的影響。
Because petroleum will be used up in this century, it is urgent to find new substitute energy. Because solar energy is clean and almost unlimited, many scientists are working on developing high efficiency and low cost solar cells. Until now, practical solar cells are silicon p-n junction structure. However, efficiency of this structure approaches theoretical limit. In this work, we will first introduce strategies used to improve cells’ performance. We will discuss effect of each part of this cell and expect to optimize it.
We also developed a new cell structure using band to band tunneling. Band to band tunneling in this structure generates many carriers even more than photo-generated carriers. Those additional carriers enlarge short circuit current very much. However, the efficiency of the above band-to-band tunneling structure is still smaller than that of conventional structure because output voltage at high output current region is too low. A gate electrode is put upon channel region. This gate voltage can change band in channel region and thus affect band to band tunneling. To cause more band to band tunneling, SiGe which has smaller bandgap is used instead of silicon. As expected, band to band tunneling in SiGe tunneling structure is more prominent and short circuit current becomes larger. However, open circuit voltage is smaller in SiGe tunneling structure. So the resultant efficiency is lower than that for the Si tunneling and the conventional structures. We will discuss effects of doping concentration, mole fraction, shallow junction and gate voltage in tunneling structure.
Finally, we will discuss lateral structure. This structure doesn’t help to improve cell performance but this structure is easy to be integrated with IC process. It is also easy for this structure to be connected in series to enlarge output voltage. We will discuss effects of channel length, thickness, and shallow junction.
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