全銅金屬化三五族太陽能電池之研究

Abstract

因為太陽能電池能將不會衰竭的太陽能直接轉化成電力，使得其在再生能源領域中，成為快速成長的產業之一。在此研究中，銅金屬取代傳統的金金屬用在砷化鎵與鍺的歐姆接觸上，以降低三五族太陽能電池的製作成本並提高其工業使用率。在本實驗中，鈀(15 nm)/鍺(150 nm)和鉑(5 nm)/鈦(50 nm)/鉑(60 nm)被分別使用在N型的砷化鎵與P型的鍺半導體作為歐姆接觸，經過退火處理後，其最低特徵電阻值為4.4 x 10-6 Ω-cm2 和6.9 x 10-6 Ω-cm2。全銅金屬化後的三接面型（磷化銦鎵/砷化銦鎵/鍺）三五族太陽能電池，在AM1.5，25 oC的量測條件下，可得轉換效率23.11%及填充因子82.48%。進一步增加聚光倍率至122倍，可得轉換效率37.21%及填充因子83.98%。在可靠度測試中，使用了250 oC的高溫與6.5 x 10-4 mA/µm2的電流長時間施加在銅金屬化後的電極上。整體而言，銅金屬化歐姆接觸成功應用在三五族三接面型太陽能電池上並具有優異的表現。

Solar cell is one of the fastest growing industries in the renewable energy field, since the solar energy could be converted into electricity directly by photovoltaic technology without the environmental pollution and the solar power will not be exhausted in the near future. In this study, copper based contacts to GaAs and Ge along with copper interconnects were developed and applied to the III-V solar cells to reduce the manufacture cost of the solar cell. Pd (15 nm)/Ge (150 nm) and Pt (5 nm)/Ti (50 nm)/Pt (60 nm) were used as the n-GaAs and p-Ge ohmic contact metals, the lowest values of specific contact resistance for the contacts were 4.4 x 10-6 Ω-cm2 and 6.9 x 10-6 Ω-cm2, respectively, after thermal annealing. The fully copper metallized InGaP/InGaAs/Ge triple-junctions solar cell shows conversion efficiency of about 23.11% and 82.48%, respectively, at AM1.5，25 oC. When the concentration ratio is further increased to 122X, the conversion efficiency and fill factor become about 37.21% and 83.98%, respectively, using these material systems. The solar cells with the proposed Cu-based structures were also subjected to high-temperature annealing (250 °C) and a high DC current (6.5 x 10-4 mA/µm2) stress test in this thesis. Overall, the solar cell adopting these Cu based contacts remained quite stable and demonstrated excellent performances after these reliability tests.