- 學位論文
以液相磊晶法成長矽於低成本冶金級矽基板之太陽能電池
Silicon Solar Cells Grown on Upgraded Metallurgical Silicon Substrates by Liquid Phase Epitaxy
摘要
中文摘要 本論文係以液相磊晶系統成長掺雜鎵之矽磊晶層做各種特性研究，並研製多晶矽太陽電池。歷年來，已經有相當多關於液相磊晶系統在以單晶矽為基板製作太陽電池之探討，單晶矽太陽電池在理論上雖擁有較高的光電轉換效率，但是相對地，在材料的製作成本上高出許多，因此，本論文以降低材料成本為考量，選擇以低成本及低純度(4N-5N)的冶金級多晶矽做為材料，同時又能達到單晶矽太陽能電池水準的效率。 在分析的部份，對於以銦做溶劑以鎵做摻雜的磊晶層品質，我們使用了Nomarski 顯微鏡、膜厚機、霍爾量測來了解鎵對矽磊晶層的影響，並建立P-型摻雜的莫耳數和載子濃度相關的完整參數。基於我們使用的是低純度的冶金級多晶矽基板，因此，我們使用SIMS量測，來觀察磊晶層是否有降低表面雜質濃度的效果。更以此為基礎，研製冶金級矽太陽電池。利用高溫擴散爐擴散製程完成PN-JUNCTION。之後以電子槍蒸鍍機來製作前電極，並運用網版印刷技術將鋁膠塗佈於晶片背面製作背電極，以完成太陽電池元件並進行效率量測。 根據實驗結果顯示，磊晶層厚度隨著實驗系統的降溫速率增加而增加，得到當我們以30 oC/min的速度降溫100分鐘，可得到20~30 um厚度的磊晶層。當摻雜0.1-0.5重量百分比的鎵於矽時，可以得到較平坦的表面。室溫下的載子濃度、移動率，由霍爾效應量測獲得，得到在鎵摻雜P-型矽時，濃度有隨著摻雜量增加的趨勢，移動率則隨著摻雜量增加而降低。元件製作完成後，經效率量測可達到10.5%轉換效率。
並列摘要
Abstract There are many reports about LPE growth of Si on single-crystal substrate, and achieve a retty good efficiency, however the cost was a greatest barrier for developing photovoltaic (PV) market. Thin silicon layers grown on an inexpensive upgraded metallurgical grade (UMG) Si substrate offer a promising alternative to conventional bulk material for solar cells comparing with other epitaxial methods. Silicon layer grown on cast UMG-Si substrates by LPE has advantages of simplicity, fast growth rate, relatively low temperature, excellent crystallinity, and erfect lattice match. This paper studies the growth of Si LPE layers on UMG-Si substrates in an In/Ga solution. Relation of gallium concentration to indium solution, we measured the electrical properties by Hall measurements, the morphology were investigated using Nomarski differential interference contrast microscope (N-DICM), and crystalline was detected by X-ray diffraction(XRD). Finally, the fabricated solar cell devices achieve a desired energy conversion efficiency. The fabrication employed p-n junction with POCl3 emitter diffusion, back contact via Al paste, front contact using e-gun evaporator, and SiNx anti-reflected (AR) coating by PECVD. We could receive the best energy conversion efficiency of 10.5% Si solar cell and its Ga weight percentage reaches to 0.5%.