薄膜太陽能電池填充因子特性研究

The fill factor characteristic research of amorphous silicon solar cell

林博鴻(Po-Hong Lin)

指導教授 ： 沈幼敏

元智大學/工程學院/先進能源碩士學位學程/碩士(2011年)

https://doi.org/10.6838/YZU.2011.00050

摘要

由於能源危機的關係，替代性能源的發展備受重視。而太陽能擁有取之不盡、用之不竭的優勢，是一個很好的替代性能源。在眾多的太陽能電池中，薄膜太陽能電池由於應用範圍廣泛，且材料成本低與輕、薄、可透光等特性，又可以與建材結合一體(BIPV)，是一個很好的研究方向。本研究利用超高頻電漿輔助化學氣相沉積系統(Very High Frequency Plasma Enhanced Chemical Vapor Deposition, VHF-PECVD)製備矽薄膜部分，並以連續式多腔體濺鍍系統(In Line Sputter)製備背後金屬電極探討不同元件結構及製程參數對矽薄膜太陽能電池所造成的影響。
實驗首先以ASAHI U-type/p-a-SiC:H/buffer layer/i-a-Si:H/n-a-Si:H/Ag結構中探討IV特性曲線的變化。利用In Line Sputter系統基板來回之特性，由來回1Run增加至4Run時，短路電流及填充因子有上升的趨勢，當基板來回4Run，金屬電極厚度為264 nm時，其Voc = 0.85 V、Jsc = 14.23 mA/cm2、FF = 61.8%及η = 7.48%。以現有結構加入背後AZO薄膜，其結構為ASAHI U-type/p-a-SiC:H/buffer layer/i-a-Si:H/n-a-Si:H/AZO/Ag，發現以電漿功率800W、AZO薄膜厚度180 nm得到較佳IV特性，Voc = 0.837 V、Jsc = 14.93 mA/cm2、FF = 68.4%及η = 8.54%。針對前接觸之改善，以氫電漿處理ASAHI基板表面，在RF Power為15 W、Pressure為90 Pa、H2為160 sccm、E/S距離為30 mm，並以10 s做表面處理，得到Voc = 0.837 V、Jsc = 15.14 mA/cm2、FF = 65.6%及η = 8.31%。另一方法，在基板與矽膜之間加入AZO薄膜，薄膜厚度在10 nm時，Voc = 0.82 V、Jsc = 15.78 mA/cm2、FF = 66.2%及η = 8.56%。
最後本實驗以雙層背電極(AZO/Ag)取代單層背電極(Ag)，預期改善元件之矽膜與金屬電極之接觸，以提高FF，進而提升太陽能電池之轉換效率。加入背後AZO結構之電池元件經120˚C， 120 min退火處理後，其Voc = 0.85 V、Jsc = 15.12 mA/cm2、FF = 70.69%及η = 9.08%；氫電漿處理之電池元件經退火處理後，其Voc = 0.82 V、Jsc = 16.11 mA/cm2、FF = 66.7%及η = 8.81%；加入前AZO結構之電池元件經退火處理後，其Voc = 0.83 V、Jsc = 16.05 mA/cm2、FF = 67.2%及η = 8.95%。由於電池轉換效率是受開路電壓、短路電流、填充因子等因素影響其大小，當改善其中一值，其他因素也跟著變動，相較於單層背電極(Ag)結構而言，雙層背電極(AZO/Ag)之FF與η皆能有所提高，經由退火處理後，FF值更可達70%以上。

關鍵字

氫化非晶矽 ； 太陽能電池 ； AZO薄膜 ； 電漿化學氣相沉積系統

並列摘要

The energy crisis causes the development of renewable energy to replace the rock oil energy. The solar energy is a distinguished renewable energy because it is in great demand at present. In a wide variety of solar cells, as a-Si solar cells with low material cost and high transmittance advantage. In this study, the pin single junction amorphous silicon solar cell were fabricated by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD), and the metal electrode (Ag or AZO/Ag) were fabricated by In Line Sputter. The different device structure and process technology on performance of amorphous silicon solar cells were investigated.
The effect of IV curve in ASAHI U-type/p-a-SiC:H/buffer layer/i-a-Si:H/n-a-Si:H/Ag solar cell structures were discussed in this study. Using the characteristics of the In Line Sputter, , we can find that Jsc and FF increased when 1Run to 4Run, and reached a maximum efficiency at 4Run with Voc = 0.85 V, Jsc = 14.23 mA/cm2, FF = 61.8% and η = 7.48%. A back double electrodes with AZO/Ag was deposted. The result, RF power = 800W, the AZO 180 nm thick shows the Voc = 0.837 V, Jsc = 14.93 mA/cm2, FF = 68.4% and η = 8.54%. The ASAHI U-type/p-layer can be improve by H2 plasma treatment or insert front AZO. We can obtained the Voc = 0.837 V, Jsc = 15.14 mA/cm2, FF = 65.6% and η = 8.31% when the H2 plasma(10s). In addition, AZO 10 nm thick with the Voc = 0.82 V, Jsc = 15.78 mA/cm2, FF = 66.2% and η = 8.56%.
Finally, the cells were annealed to improve the contact between silicon and metal electrode to increase the FF and conversion efficiency of thin film solar cells. After post annealing at 120˚C for 120 minute, the optimized single junction a-Si:H solar cell with back AZO was ASAHI U-type/p-a-SiC:H/buffer layer/i-a-Si:H/n-a-Si:H/AZO/Ag, the Voc = 0.85 V, Jsc = 15.12 mA/cm2, FF = 70.69% and η = 9.08%; H2 plasma treatment(10s), the Voc = 0.82 V, Jsc = 16.11 mA/cm2, FF = 66.7% and η = 8.81%; insert front AZO 10 nm thick, the Voc = 0.83 V, Jsc = 16.05 mA/cm2, FF = 67.2% and η = 8.95%. It can be also concluded that after post annealing of AZO/Ag is beneficial for improving fill factor and conversion efficiency.

並列關鍵字

hydrogenated amorphous silicon ； a-Si:H；solar cell；AZO film；VHF-PECVD

參考文獻

[2]D. E. Carlson, C. R. Wronski,“Amorphous silicon solar cell”,Appl. Phys. Lett. Vol. 28,(1976), pp.11.

[3]D. L. Staebler, C. R. Wronski“Reversible Conductivity Changes in Discharge-Produced Amorphous Si”, Appl. Phys. Lett, Vol. 31, (1977), pp. 292-294

[6]K. Yamamoto, M. Toshimi, T. Suzuki, Y. Tawada, T. Okamoto, A. Nakajima. Thin film poly-Si solar cell on glass substrate fabricated at low temperature, MRS Spring Meeting, April 1998, San Francisco.

[7]J. Meier, J. Sitznagel, U. Kroll, C. Bucher, S. Fay, Moriarty T, Shah A. Potential of amorphous and microcrystalline silicon solar cells. Thin Solid Films 2004; 451-452: 518-524.

[17]Tawada, Y., H. Okamoto, and Y. Hamakawa, Appl. Phys. Lett., 39, 237 (1981).