各種金屬電極搭配氧化鉬電洞選擇性傳輸層對網印式單晶矽太陽能電池光電特性之影響研究

Effects of Various Metal Electrodes and Molybdenum Oxide Hole-Selective Contact Layer on Photovoltaic Characteristics of Screen-Printed Monocrystalline Silicon Solar Cells

張瑞居(Jui-Chu Chang)

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

本論文研究探討各種金屬電極搭配氧化鉬電洞選擇性傳輸層對網印式單晶矽太陽能電池光電特性之影響研究。由於太陽能電池背面鈍化後通常採用雷射局部開孔製程，因而造成表面雷射損傷。同時，太陽能電池背面若披覆一層鈍化層，可改善載子復合效應及增加背面紅外線反射效果，因為基板為正型矽基板，且氧化鉬與正型矽基板的介面能帶只允許電洞傳輸，不允許電子越過介面。因此本研究採用蒸鍍氧化鉬電洞選擇性傳輸層，可避免使用到雷射開孔製程，同時兼顧鈍化效果降低載子復合效應，增加開路電壓。首先，探討氧化鉬暴露於大氣對網印式單晶矽太陽能電池所產生的效應，接著改變的實驗參數包含氧化鉬的厚度、各種金屬電極如蒸鍍鋁、蒸鍍銀、蒸鍍銅、蒸鍍鎳/銀堆疊層、網印銀及網印鋁等。最後，分別探討氧化鋁披覆鎢舟重複使用次數，蒸鍍基板中加熱對氧化鉬的影響以及使用HF/HNO3/H2O混合溶液對矽基板背面施行平坦化的效應。
實驗結果顯示，蒸鍍氧化鉬電洞選擇性傳輸層後經破真空接觸到大氣中對太陽能電池的光電轉換效率影響很大，可從16.7 %下降到0 %。當破真空時間為10分鐘時，對太陽能電池的光電轉換效率只有0.2 %，因此若考慮製程整合時其暴露於大氣時間可採用10分鐘以內對於效率的影響較小。氧化鋁披覆鎢舟重複使用對效率影響不大，基板加熱對氧化鉬層沒有提升效率以及藉由使用HF/NHO3/H2O混合溶液蝕刻時間越久光電轉換效率下降。另外隨著氧化鉬的厚度增加元件光電轉換效率增加，當使用蒸鍍鋁、蒸鍍銀、蒸鍍銅及蒸鍍鎳/銀堆疊層等當太陽能電池的背電極時，氧化鉬的厚度為30 nm搭配蒸鍍銀有較佳的元件光電轉換效率為17.7 %。當使用網印銀及網印鋁當太陽能電池的背電極時，其最佳參數為蒸鍍氧化鉬電洞選擇性傳輸層厚度為10 nm搭配網印鋁電極，可獲得最佳光電轉換效率為18.1 %。

關鍵字

熱蒸鍍 ； 氧化鉬 ； 電洞選擇性傳輸 ； 單晶矽太陽能電池 ； 光電特性

並列摘要

In this thesis, the effects of various metal electrodes and molybdenum oxide hole-selective contact layer on photovoltaic characteristics of screen-printed monocrystalline silicon solar cells (SPMSSCs) were investigated. The laser damage was formed by the laser contact process in passivation layer. Moreover, the carrier recombination effects and the reflection of the rear side can be enhanced by the backside passivation layer. Since the substrate is p-type silicon and the hole can be passed through the molybdenum oxide (MoO3)/p-type silicon interface, evaporated MoO3 was used as the hole-selective layer of the SPMSSCs to avoid the laser process and reduce the recombination effects. First, the effects of MoO3 in air on the photovoltaic characteristics of the SPMSSCs were addressed. Next, the effects of the thickness of the MoO3 and various metal electrodes on the photovoltaic characteristics of the SPMSSCs were presented. Finally, to explore the number of repeated use of aluminum coated tungsten boat, effect of molybdenum oxide deposition substrate heating and the effects of flat rear side were examined.
The results show that the conversion efficiency (CE) was reduced dramatically from 16.7 % to 0 % with increasing time. On the other hand, only 0.2 % CE reduction was achieved below 10 min. Thus, the MoO3 can be explored in the air for 10 min before metal deposition. The use of alumina overturned tungsten boat has little effect on efficiency, substrate heating does not improve the efficiency of the molybdenum oxide layer and the longer the etch time of the HF/NHO3/H2O mixed solution, the longer the photoelectric conversion efficiency.The CE increase with increasing the thickness of the MoO3. The better thickness is 30 nm. Amount various metal electrode including evaporated Al, Ag, Cu and Ni/Ag, the Ag electrode is the best. The CE of 17.7 % was demonstrated by the evaporated Ag electrode and the thickness of 30 nm of the MoO3. Furthermore, the CE of 18.1 % was demonstrated by screen-printed Al electrode and the thickness of 10 nm of the MoO3.

並列關鍵字

Thermal evaporation ； molybdenum oxide ； hole-selective layer ； monocrystalline silicon solar cells ； photovoltaic characteristics

參考文獻

[1] Y. Hwang, C. S Park, J. Kim, J. Kim, J. Y. Lim, H. Choi, J. Jo, E. Lee, “Effect of laser damage etching on i-PERC solar cells,” Renewable Energy, 79, pp. 131-134, 2015.

[2] M. Kim, S. Park, D. Kim, “Highly efficient PERC cells fabricated using the low cost laser ablation process,” Solar Energy Materials & Solar Cells, 117, pp. 126-131, 2013.

[3] A. Uruena, L. Tous, F. Duerinckx, I. K. Filipek, E. Cornagliotti, J. John, R. Mertens, J. Poortmans, “Understanding the mechanisms of rear reflectance losses in PERC type silicon solar cells,” Energy Procedia, 38, pp. 801-806, 2013.

[4] J. Kim, Y. Hwang, J. Kim, J. Lim, E. Lee, “Investigation of rear side selective laser ablation and damage etching process for industrial PERC solar cells,” Energy Procedia, 55, pp. 791-796, 2014.

[5] J. Meyer, S. Hamwi, M. Kroger, W. Kowalsky, T. Riedl, A. Kahn, “Transition metal oxides for organic electronics: energetics, device physics and applications,” Advanced Materials, 24, pp. 5408-5427, 2012.