Fabrication of silicon nanowire based solar cells using TiO 2 /Al 2 O 3 stack thin films
- PDF / 1,081,033 Bytes
- 8 Pages / 432 x 648 pts Page_size
- 4 Downloads / 191 Views
MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.40
Fabrication of silicon nanowire based solar cells using TiO2/Al2O3 stack thin films Yasuyoshi Kurokawa1,2, Ryota Nezasa1, Shinya Kato3, Hisashi Miyazaki4, Isao Takahashi1, Noritaka Usami1 1
Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8603, Japan 2 PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Hon-cho, Kawaguchi-shi, Saitama, 3320012, Japan 3 Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi, 466-8555, Japan 4 Department of Materials Science and Engineering, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka-shi, Kanagawa 239-8686, Japan
ABSTRACT
To improve conversion efficiency of silicon nanowire (SiNW) solar cells, it is very important to reduce the surface recombination rate on the surface of SiNWs, since SiNWs have a large surface area. We tried to cover SiNWs with aluminum oxide (Al2O3) and titanium oxide (TiO2) by atomic layer deposition (ALD), since Al2O3 grown by ALD provides an excellent level of surface passivation on silicon wafers and TiO2 has a higher refractive index than Al2O3, leading to the reduction of surface reflectance. The effective minority carrier lifetime in SiNW arrays embedded in a TiO2/Al2O3 stack layer of 94 μsec was obtained, which was comparable to an Al2O3 single layer. The surface reflectance of SiNW solar cells was drastically decreased below around 5% in all of the wavelength range using the Al2O3/TiO2/Al2O3 stack layer. Heterojunction SiNW solar cells with the structure of ITO/p-type hydrogenated amorphous silicon (a-Si:H)/n-type SiNWs embedded in Al2O3 and TiO2 stack layer for passivation/n-type a-Si:H/back electrode was fabricated, and a typical rectifying property and open-circuit voltage of 356 mV were successfully obtained.
INTRODUCTION Silicon nanowires (SiNWs) have recently attracted much attention as one of the novel photovoltaic materials. It is expected that SiNW solar cells [1-13] with a relatively thin absorber layer will have the potential to realize sufficient photocurrent [14-22]. It is very important to reduce the surface recombination rate on the surface of SiNWs, since SiNWs have a large surface area. We confirmed the high passivation effect of Al 2O3 deposited by atomic layer deposition (ALD) on SiNW arrays by measuring the effective minority carrier lifetime [23,24]. Moreover, we fabricated heterojunction SiNW (HJSiNW) solar cell structure, and confirmed the solar cell performance [25]. To obtain SiNW solar cells with higher efficiency, it is needed to reduce internal reflection in SiNW solar cells. The previous structure of SiNW solar cells and the reflectance of the fabricated SiNW solar cell are shown in Figs. 1(a, b), respectively [26]. The high
(a) 50 nm
0.8
ITO
Al2O3
p-type a-Si:H
Reflectance
Downloaded from https://www.cambridge.org/core. Cornell University Library, on 29 Jan 2018 at 09:31:16, subject to the Cambridge Core terms of use, available at https:
Data Loading...
