利用不同材料與結構提升單接面非晶矽薄膜太陽能電池效率之研究

Abstract

本研究利用射頻電漿輔助化學氣相沉積系統來沉積不同的材料與結構，來增加太陽電池吸收層的吸收，以進一步提昇單接面非晶矽薄膜太陽能電池之效率。首先，沉積低折射率非晶氮化矽薄膜，並將非晶氮化矽薄膜沉積在玻璃基板與透明導電薄膜間當作抗反射層，比較固定折射率與漸變折射率的非晶氮化矽在光學性質，並找出最佳化的厚度，以增加太陽電池的效率。藉由非晶氮化矽反射膜的添加，使單接面非晶矽薄膜太陽能電池效率提升4.8%。接著，比較不同能隙與導電性的p型氫化非晶碳化矽薄膜所製作的太陽能電池。進一步研究結合p型微晶矽與非晶碳化矽結構以及p型碳化矽與碳化矽結構對薄膜太陽能電池效能上的影響。使用雙層p型碳化矽結構可進一步提升效率從9.1%到9.25%。最後，使用n型微晶氧化矽取代原本的n型非晶矽，以及取代n型非晶矽與透明氧化導電層作為背反射結構。藉由光學反射的增加提升光電轉換效率。本研究最佳之非晶矽薄膜太陽能電池轉換效率已提升至10.13%，其中開路電壓，短路電流密度，填充因子分別為0.9 V，15.27 mA/cm2以及73.75%。

In this study, hydrogenated amorphous silicon thin-film solar cell was prepared by plasma-enhanced chemical vapor deposition (PECVD) system at 27.12 MHz. In order to improve the cell performance, different materials and structures were prepared to enhance the light absorption in the absorber active layer. First, the lower- refractive-index hydrogenated amorphous silicon nitride (a-SiNx:H) was deposited between the glass substrate and the transparent conductive oxide (TCO) layer to serve as the antireflection (AR) coatings. The performance of the devices having a-SiNx:H with the constant refractive index was compared with the devices having a-SiNx:H with the graded refractive index. The thickness of a-SiNx:H was also adjusted to optimize the performance of solar cells. By inserting 80 nm a-SiNx:H AR coating, a-Si:H single-junction cell had a relative increase of 4.8% in efficiency. Second, devices with different p-type window layers was compared. Hydrogenated microcrystalline silicon (µc-Si:H)/hydrogenated amorphous silicon cabide (a-SiCx:H) and a-SiCx:H/a-SiCx:H double p-layer structures were utilized in devices. The combination of p-layers with better optical and electrical properties was investigated to optimize the cell performance. The efficiency of a-Si:H cells having a-SiCx:H/a-SiCx:H window structure was improved from 9.1% to 9.25%. Finally, the n-doped microcrystalline silicon oxide (µc-SiOx:H(n)) was served as n-layer in solar cells. Besides, µc-SiOx:H(n)/Ag structure was used to replace a-Si:H(n)/TCO/Ag as back reflector (BR) structure. The increase in the optical reflection by the oxide layers on the back side improved the cell performance. The best conversion efficiency in this study was 10.13% with Voc=900.1 mV, Jsc=15.27 mA/cm2, FF=73.75%.