脈衝調變式電漿輔助化學氣相沉積之氮化矽抗反射膜薄對太陽能電池之電位誘發衰退效應之影響

Abstract

太陽能電池模組系統中存在著一種電位誘發衰退(PID)效應，此種效應會讓發電功率大幅度的下降。自從2005年由SunPower公司提出後，產業界就開始關注PID 的研究和討論。避免PID效應的方法在電池端、模組端以及系統端都有方案可以解決，但是須考慮到成本、轉換效率、電池片生產量等問題。選擇在電池端增加a-SiNx:H薄膜的折射率，來達到抗PID效果是最常見的方法，但是通常會伴隨著轉換效率降低的結果。本實驗以電漿輔助化學氣相沉積(PECVD)方式製作a-SiNx:H薄膜，在實驗中將傳統式連續性電漿方式改為脈衝調變電漿方式，利用改變a-SiNx:H薄膜特性方式來增加抗PID能力，同時又不降低轉換效率。 為了解a-SiNx:H薄膜特性如何影響PID效應及轉換效率，實驗中使用連續性電漿及脈衝調變電漿，分別製作折射率2.07、2.11、2.16的薄膜，進行48及96小時PID測試比較，並分析a-SiNx:H薄膜光學性質、電性量測、HF蝕刻率以及成份組成。考慮到a-SiNx:H薄膜厚度會不會影響到抗PID性能，實驗中也使 用連續性電漿製備相同折射率但是厚度不一樣的a-SiNx:H薄膜進行PID測試。 最後探討為何脈衝調變電漿薄膜在抗PID的能力上會輸給連續性電漿薄膜，並以降低脈衝調變電漿的工作週期為研究方向，增加脈衝調變電漿薄膜Si含量，以提高抗PID能力。

A phenomenon called potential-induced degradation (PID) has been found out in solar cell module by SunPower Co. in 2005, which can cause the power conversion efficiency of solar cells drop sharply. Since that, solar cell industries and academic researchers have put a lot of effort to investigate PID and find out solutions for it. There are different ways to solve PID depending on the levels of modules and system. In consideration of cost, conversion efficiency, throughput and other issues, the typical solution is to increase the refractive index of a-SiNx:H thin film of solar cell. However, the conversion efficiency decreases as well. In general, a-SiNx:H thin film of solar cell is deposited by plasma enhanced chemical vapor deposition (PECVD). In this experiment, we investigated the properties of a-SiNx:H thin films deposited by conventional continuous mode and pulse-modulated mode of PECVD and compared their performances of PID resistance. To understand how the properties of a-SiNx:H film influence on PID effect and conversion efficiency, a-SiNx:H films of solar cells with refractive index of 2.07, 2.11, and 2.16 are deposited by continuous and pulse-modulated mode, respectively. Then those solar cells were performed PID test for 48 and 96 hours and the optical properties, electrical properties, etching rate, and composition of these a-SiNx:H films were investigated. Considering whether thickness of a-SiNx:H film influence on performance of anti-PID, solar cells with different thickness of a-SiNx:H films deposited by continuous mode are performed PID test. Finally, we discussed why the performance of PID resistance of a-SiNx:H film deposited by continuous mode is better than that deposited by pulse-modulated mode. For the future work, the PID resistance of a-SiNx:H films deposited by pulse-modulated mode can be improved by increasing the composition of Si by decreasing the duty cycle of pulse-modulated plasma.