高效率雙接面矽基薄膜太陽能電池製備與特性之研究

Fabrication and Characterization of High Efficiency Tandem (a-Si/a-Si) Thin Films Solar Cell

林揚士(Yang-Shih Lin)

指導教授 ： 蔡丕椿

共同指導教授 ： 連水養

國立虎尾科技大學/工程學院/材料科學與綠色能源工程研究所/碩士(2010年)

摘要

本研究利用高頻電漿輔助化學氣相沈積系統(High Frequency Plasma Enhanced Chemical Vapor Deposition, HF-PECVD)製備pin單接面及pin/pin雙接面非晶矽薄膜太陽能電池，並探討不同元件結構及製程技術對矽薄膜太陽電池特性之影響。
首先在(glass/TCO/p-a-SiC:H/b-a-SiC:H/i-a-Si:H/n-a-Si:H/TCO/metal)結構中，我們探討不同本質層厚度對效率的影響，由結果發現，當本質層厚度由200 nm提升到300 nm時，開路電壓(Open Circuit Voltage, Voc)及短路電流(Short Circuit Current density, Jsc)會有上升的趨勢，當本質層厚度增加到350 nm時，可得到最佳的電池轉換效率。其中，Voc為0.83 V，Jsc為15.9 mA/cm2，填充因子(Fill Factor, F.F.)為69.3%，轉換效率(Conversion Efficiency, h)為9.15%，但當本質層增加至400 nm時，效率反而下降。雙接面(glass/TCO/p-a-SiC:H/b-a-SiC:H/i-a-Si:H/n-a-Si:H/buffer/p-a-SiC:H/b-a-SiC:H/i-a-Si:H/n-a-Si:H/TCO/metal)結構之疊層非晶矽薄膜太陽能電池而言，我們藉由上層本質層(i1)與下層本質層(i2)厚度的調變來得到最佳電流匹配，減少載子復合損失，以提高太陽能電池的轉換效率。其中本質層(i2/i1)厚度比例範圍由2調變到11，當比例為6時，可得到最佳之太陽能電池特性，其中Voc=1.57 V，Jsc為6.38 mA/cm2，F.F.為73.5%，h為7.41%。
最後，本實驗以氧化鋅摻雜鋁(Al doped ZnO, AZO)/銀(Ag)雙層電極結構取代原先的單層背電極，並搭配退火處理，期望改善元件之矽膜與金屬界面間之接觸，以提高薄膜太陽能電池之轉換效率。單接面非晶矽薄膜太陽能電池經150℃、120分鐘退火後，其Voc為0.82 V，Jsc為17.0 mA/cm2 ，F.F.為72.6%，h為10.1%，其相較單層背電極結構而言，太陽電池轉換效率可提升約1%。對tandem而言，太陽電池效率分別為Voc=1.59 V，Jsc為7.96 mA/cm2，F.F.為70.4%，h為8.95%，整體效率較單層背電極約可提升約1.5%。由此可知，雙層電極結構的確有助於提升太陽能電池特性。

關鍵字

高頻電漿輔助化學氣相沈積系統 ； 非晶矽薄膜太陽能電池 ； 疊層非晶矽薄膜太陽能電池 ； 氧化鋅摻雜鋁

並列摘要

In this study, the pin single-junction and pin/pin double junction amorphous silicon solar cell were fabricated by high frequency plasma enhanced chemical vapor deposition (HF-PECVD) process. The different device structure and process technology on performance of amorphous silicon solar cells were investigated.
The effect of thickness of intrinsic layer in glass/TCO/p-a-SiC:H/b-a-SiC:H /i-a-Si:H/n-a-Si:H/TCO/metal solar cell structures were discussed in this study. The results showed that Voc and Jsc increased when the thickness of intrinsic layer increased from 200 nm to 300 nm and reached a maximum efficiency at optimum 350 nm with Voc of 0.83 V, Jsc of 15.9 mA/cm2, F.F. of 69.3%, and h of 9.15%. However, the conversion efficiency decreased when the thickness increased from 300 nm to 400 nm.
The efforts were made to make tandem (glass/TCO/p-a-SiC:H/b-a-SiC:H /i-a-Si:H/n-a-Si:H/buffer/p-a-SiC:H/b-a-SiC:H/i-a-Si:H/n-a-Si:H/TCO/metal, a-Si:H/a-Si:H) hydrogenated amorphous thin film solar cells structures for higher efficiency and the thicknesses of i-layer in both top cell (i1) and bottom cell (i2) were also changed for obtaining best matching current, and reducing recombination. The i2/i1 ratio were ranged from 2 to 11, and the characteristics of solar cell performed well when the optimum proportion of i2/i1 reached 6 with the Voc of 1.57 V, Jsc of 6.38 mA/cm2, F.F. of 73.52%, and h of 7.41%.
Finally, a back double electrodes with Al doped ZnO(AZO)/Ag was deposited for replacing Ag. After that, the cells were annealed to improve the contact between silicon and metal for higher efficiency of thin film solar cells. After post-annealing at 150 ℃for 120 minute, the optimized a-Si:H thin film solar cells reached Voc of 0.82 V, Jsc of 17 mA/cm2, F.F. of 72.6%, and h of 10.11% . Compared to previous conversion efficiency, it raised almost 1 %. Same post-annealing process was done for the tandem (a-Si:H/a-Si:H) hydrogenated amorphous thin film solar cells which reached Voc of 1.59 V, Jsc of 7.96 mA/cm2, F.F. of 70.4%, and h of 8.95% which raised 1.5%. Obviously the post-annealing process lifting the efficiency of the a-Si:H thin film solar cells. It can be also concluded that the deposition of AZO/Ag is beneficial for improving cell efficiency.

並列關鍵字

High Frequency Plasma Enhanced Chemical Vapor Deposition ； hydrogenated amorphous thin film solar cells ； tandem hydrogenated amorphous thin film solar cells ； Al doped ZnO

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