Low-temperature high-mobility amorphous IZO for silicon heterojunction solar cells

Journal Article · Mon Jul 13 00:00:00 EDT 2015 · IEEE Journal of Photovoltaics

DOI:https://doi.org/10.1109/JPHOTOV.2015.2450993· OSTI ID:1229743

Morales-Masis, Monica ^[1]; Martin De Nicolas, Silvia ^[1]; Holovsky, Jakub ^[2]; De Wolf, Stefaan ^[1]; Ballif, Christophe ^[1]

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1. École Polytechnique Fédérale de Lausanne (EPFL), Neuchatel (Switzerland)
2. Institute of Physics ASCR, Prague (Czech Republic); Czech Technical Univ., Prague (Czech Republic)

Parasitic absorption in the transparent conductive oxide (TCO) front electrode is one of the limitations of silicon heterojunction (SHJ) solar cells efficiency. To avoid such absorption while retaining high conductivity, TCOs with high electron mobility are preferred over those with high carrier density. Here, we demonstrate improved SHJ solar cell efficiencies by applying high-mobility amorphous indium zinc oxide (a-IZO) as the front TCO. We sputtered a-IZO at low substrate temperature and low power density and investigated the optical and electrical properties, as well as subband tail formation-quantified by the Urbach energy (E_U)-as a function of the sputtering oxygen partial pressure. We obtain an E_U as low as 128 meV for films with the highest Hall mobility of 60 cm²/Vs. When comparing the performance of a-IZO films with indium tin oxide (ITO) and hydrogenated indium oxide (IO:H), we find that IO:H (115 cm²/Vs) exhibits a similar E_U of 130 meV, while ITO (25 cm²/Vs) presents a much larger E_U of up to 270 meV. The high film quality, indicated by the low E_U, the high mobility, and low free carrier absorption of the developed a-IZO electrodes, result in a significant current improvement, achieving conversion efficiencies over 21.5%, outperforming those with standard ITO.

• Research Organization: École Polytechnique Fédérale de Lausanne (EPFL), Neuchatel (Switzerland)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: EE0006335
• OSTI ID: 1229743
• Journal Information: IEEE Journal of Photovoltaics, Vol. 5, Issue 5; ISSN 2156-3381
• Publisher: IEEE
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
amorphous indium zinc oxide
electron mobility
heterojunction
indium tin oxide
silicon
solar cells
transparent conductive oxides
Urbach energy