各種處理方式的氧化鉬電洞選擇性薄膜對網印式單晶矽太陽能電池之光電特性影響研究

Effects of Various Treated Molybdenum Oxide Hole-Selective Films on Photovoltaic Characteristics of Screen-Printed Monocrystalline Silicon Solar Cells

陳姵文(Pei-Wen Chen)

指導教授 ： 鄭錦隆

國立虎尾科技大學/電機資訊學院/光電工程系光電與材料科技碩士班/碩士(2017年)

摘要

本研究論文探討經過各種處理方式的氧化鉬電洞選擇性傳輸材料對網印式單晶矽太陽能電池之光電特性影響，採用氧化鉬電洞選擇性材料當作矽基板的鈍化層是基於能帶彎曲的物理機制，只允許電洞傳輸，而不使電子通過接面，因而避免使用雷射開孔製程，導致矽基板產生雷射損傷。
本研究首先探討(1)熱蒸鍍二氧化鉬薄膜前，去除矽基板之原生氧化層處理方法，其處理方法包含以Buffer Oxide Etch及稀氟酸兩種蝕刻液；(2)改變蒸鍍背面銀電極厚度，研究銀電極厚度改變之影響；(3)針對旋塗抗蝕刻阻擋膠次數之正電極包覆性進行探討；(4)以HF/HNO3/DIW之混合藥液平坦化矽基板，分析背面平坦化及糙化效果特性；(5) 分析以三氧化鉬在真空底下或在氮氣氛圍下對熱蒸鍍後的三氧化鉬特性影響；(6)最後改變氧化鉬組成比，研究二氧化鉬與三氧化鉬之差異性。
實驗結果顯示，與BOE藥液相比較，利用稀氟酸去除原生氧化層後，並搭配二氧化鉬厚度為40 nm時可獲得較佳的光電轉換效率提升，其平均增加值（∆η%）為0.56%；改變蒸鍍背面銀電極厚度時，銀電極的厚度500 nm及750 nm之∆η%值，兩者相距不大，因成本考量仍採用銀電極厚度為500 nm之銀背電極；旋塗兩次抗蝕刻阻擋膠後，相對與一次旋塗可獲得較佳的光電轉換效率提升，其∆η%值達0.72%；利用HF/HNO3/DIW之混和藥液進行背面平坦化處理，證實背面平坦化處理無法增加轉換效率；與氮氣環境下相比，在真空環境下，其轉換效率是較佳的；最後在蒸鍍二氧化鉬與三氧化鉬相比，當蒸鍍二氧化鉬厚度30 nm，銀電極500 nm能得到最高其∆η%值達1.67%，其平均開路電壓為0.653 V，平均短路電流為35.3 mA/cm2，平均填充因子為80.1%，最高光電轉換效率為18.7%。

關鍵字

氧化鉬 ； 電洞選擇性 ； 熱蒸鍍 ； 單晶矽太陽能電池 ； 處理方式

並列摘要

Effects of various treated molybdenum oxide hole-selective films on photovoltaic characteristics of screen-printed monocrystalline silicon solar cells (SPMSSCs) were investigated in this thesis. The molybdenum oxide (MoOx) was proposed as the rear passivation layer of the p-type silicon substrate due to the energy band diagram of Si/MoOx contact. The band bending at the p-type Si/MoOx interface, which allows the holes transport and has the ability to block electrons pass through the interface. Thus, the laser opening local contacts processes can be avoided. Therefore, the laser damage was keep away from the silicon substrate.
First, the native oxides were removed by buffer-oxide-etch (BOE) or dilute HF (DHF) solution prior to thermally evaporated MoO2 films. Then, effects of various thicknesses of sliver electrodes on photovoltaic characteristics of SPMSSCs were achieved. The number of spin-coated polymer to protect silver electrode of the front side was explored. Moreover, the surface morphologies, including textured and flatted surface, were demonstrated by HF/HNO3/DIW mixed solution. Furthermore, the effects of the thermally evaporated MoO3 with nitrogen (N2) gas or vacuum environment on photovoltaic characteristics of SPMSSCs were compared. Finally, the effects of the stoichiometric of the MoOx thin films on photovoltaic characteristics of the SPMSSCs were examined.
The results indicate that the enhanced conversion efficiency (CE) for the samples with the DHF treatment was better than that of the BOE ones. The CEs of the SPMSSCs with 500 and 750 nm silver electrodes were identical. Thus, the silver electrode with 500 nm was used. The achievement of CE improvement of around 0.72% absolute for SPMSSCs with two layers polymer protection was more preferable than that of the samples with one layer polymer protection. The CE improvement of the SPMSSCs with rear textured surface was more advantageous than the samples with flatted surface. The CE improvement of the SPMSSCs with MoO3 under vacuum ambient was more valid than the samples with MoO3 under nitrogen ambient. The CE improvement of the SPMSSCs with MoO2 was more effective than the samples with MoO3. Finally, the SPMSSCs with a CE of 18.7%, an open-circuit voltage of 653 mV, a short-circuit density of 35.3 mA/cm2, and a fill factor of 80.1%, were demonstrated. Compared with the samples with Al pastes as the rear electrode, the achievement of CE improvement of around 1.67% absolute for SPMSSCs with MoO2/Ag stacked film as rear electrode was demonstrated.

並列關鍵字

Molybdenum oxide ； hole-selective ； thermal evaporation ； monocrystalline silicon solar cells ； treatment methods

參考文獻

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