Solution-Processed Titanium Oxide for Rear Contact Improvement in Heterojunction Solar Cells

Yu-Tsu Lee, Fang-Ru Lin 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
Zingway Pei: Department of Electrical Engineering, National Chung Hsing University, Taichung 40227, Taiwan

Energies, 2020, vol. 13, issue 18, 1-9

Abstract: In this work, we demonstrated a heterojunction Si solar cell utilizing chemically grown titanium oxide (TiO x ) as an electron-selective contact layer at its rear surface. With TiO x , the rear surface was passivated to reduce carrier recombination. The reverse saturation current, which is an indicator of carrier recombination, exhibited a 4.4-fold reduction after placing a TiO x layer on the rear surface. With reduced recombination, the open-circuit voltage increased from 433 mV to 600 mV and consequently, the power conversion efficiency (PCE) increased from 9.57 to 14.70%. By X-ray photoemission spectroscopy, the surface passivation was attributed to a silicon oxide interfacial layer formed during the chemical growth process. This passivation results in a 625 cm/s surface recombination velocity for the TiO x -passivated Si surface, which is 2.4 times lower than the sample without TiO x , ensuring the carriers pass through the rear contact without extensive recombination. According to these results, the band alignment for the heterojunction solar cell with and without a TiO x rear contact layer was plotted, the reduced interfacial recombination and the electron and hole blocking structure are the main reasons for the observed efficiency enhancement.

Keywords: titanium oxide; electron-selective; chemical grown; surface passivation; heterojunction solar cell (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: 2020
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