Low-Temperature, Chemically Grown Titanium Oxide Thin Films with a High Hole Tunneling Rate for Si Solar Cells

Yu-Tsu Lee, Fang-Ru Lin, Ting-Chun Lin, Chien-Hsun Chen and Zingway Pei
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Yu-Tsu Lee: Department of Electrical Engineering, National Chung Hsing University, Taichung 40227, Taiwan
Fang-Ru Lin: Department of Electrical Engineering, National Chung Hsing University, Taichung 40227, Taiwan
Ting-Chun Lin: Department of Electrical Engineering, National Chung Hsing University, Taichung 40227, Taiwan
Chien-Hsun Chen: Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, Chutung 310, Taiwan
Zingway Pei: Department of Electrical Engineering, National Chung Hsing University, Taichung 40227, Taiwan

Energies, 2016, vol. 9, issue 6, 1-10

Abstract: In this paper, we propose a chemically grown titanium oxide (TiO 2 ) on Si to form a heterojunction for photovoltaic devices. The chemically grown TiO 2 does not block hole transport. Ultraviolet photoemission spectroscopy was used to study the band alignment. A substantial band offset at the TiO 2 /Si interface was observed. X-ray photoemission spectroscopy (XPS) revealed that the chemically grown TiO 2 is oxygen-deficient and contains numerous gap states. A multiple-trap-assisted tunneling (TAT) model was used to explain the high hole injection rate. According to this model, the tunneling rate can be 10 5 orders of magnitude higher for holes passing through TiO 2 than for flow through SiO 2 . With 24-nm-thick TiO 2 , a Si solar cell achieves a 33.2 mA/cm 2 photocurrent on a planar substrate, with a 9.4% power conversion efficiency. Plan-view scanning electron microscopy images indicate that a moth-eye-like structure formed during TiO 2 deposition. This structure enables light harvesting for a high photocurrent. The high photocurrent and ease of production of chemically grown TiO 2 imply that it is a suitable candidate for future low-cost, high-efficiency solar cell applications.

Keywords: titanium oxide; chemically grown; heterojunction; band alignment; hole tunneling (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2016
References: View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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