2015年 第76回応用物理学会秋季学術講演会

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13 半導体 » 13.1 Si系基礎物性・表面界面・シミュレーション

[15p-PA4-1~5] 13.1 Si系基礎物性・表面界面・シミュレーション

2015年9月15日(火) 16:00 〜 18:00 PA4 (イベントホール)

16:00 〜 18:00

[15p-PA4-5] Nano holes on micro pyramids: modulated surface texturing with neutral beam for the application of optical trapping in Si Solar cells

〇(PC)Halubai Sekhar1, Yasuhiro Kida1, Mohammad Maksudur Rahman2, Tomohiro Kubota2, Seiji Samukawa2,3, Hidetaka Takato1, Michio Kondo1 (1.Fukushima Renewable Energy Institute, AIST, Japan, 2.Institute of Fluid Science, Tohoku University, Sendai, Japan, 3.WPI Advanced Institute for Materials Research, Tohoku University, Sendai, Japan)

キーワード:Nano holes,Micro pyrmaids,Neutral beam modulated surface

Introduction: Silicon is a stable, eco-friendly, abundant and occupy the present PV market share more than 85%, and our research mainly focus on to reduce the production cost by developing high efficiency, thin (<100 m) light weight PERC bifacial type Si solar modules in large scale for mass production. Si is high refractive index (n = 3.4) and indirect bandgap material, more than 30% of incident light is reflected from the front surface and needs more thick Si (1000 µm) to absorb transmitted light. We propose making nano holes on micro pyramids will reduce the surface reflections to minimum and increase the optical absorption through increasing the path lengths of transmitted light inside Si.
Experiments: CZ p-Si (100) with thickness of 180 µm and resistivity of 1-5 ohm-cm wafers were used to form micro pyramids by wet etching. The mixture of Cl2, SF6 and O2 neutral beam [1] were used to make holes on micro pyramids, to determine the etch profile use the cross-sectional view by using FE-SEM. Anti-reflection properties were measured using UV-Vis spectrometer which contains the integrated sphere.
Results and Discussions: Wet etching was performed to generate micro pyramids with a size of 5 to 6 microns and as shown in Fig. 1(a), which decrease the surface reflectance 20 to 9 % in the wavelength range from 400 to 1020 nm shown in Fig. 1 (b). We utilize the concept of multiple reflection in nano holes on the surface of micro pyramids will reduce the reflectance below 9%. Mask less texturing was performed to make the nano holes using Cl2, SF6, and O2 neutral beams (NB) is to generate small to big hole on the surface of micro pyramids and as shown in Fig 1(b). The measured reflectance spectrum of NB modified samples not decrease much due to partial etch out of the micro pyramids, we are optimizing the gas chemistry to get best anti-reflective modulated surface texture for photovoltaic device.