Application of TiO 2 /Ag/TiO 2 as an Ohmic Contact to an AlGaAs Layer in a GaAs Solar Cell

Petko Vitanov, Malina Milanova (), Hristosko Dikov and Nikolay Petkov
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Petko Vitanov: Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd, 1784 Sofia, Bulgaria
Malina Milanova: Central Laboratory of Applied Physics, Bulgarian Academy of Sciences, 61 Sanct Petersburg Blvd, 4000 Plovdiv, Bulgaria
Hristosko Dikov: Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd, 1784 Sofia, Bulgaria
Nikolay Petkov: Physical Sciences, Munster Technological University, Rosa Avenue, Bishopstown, Cork, Ireland and Tyndall National Institute, Lee Maltings, T12 R5CP Cork, Ireland

Energies, 2023, vol. 16, issue 10, 1-10

Abstract: This paper investigates the possibility of using a nanolaminate TiO 2 /Ag/TiO 2 structure as a transparent conductive coating on GaAs solar cells. A novel result is that this structure forms an Ohmic contact to Al-rich AlGaAs, which is used as a “window” layer in GaAs-based solar cells. The TiO 2 /Ag/TiO 2 structure is deposited by RF magnetron sputtering at room temperature. This nanolaminate coating has good optical and electrical properties: a high transmittance of 94% at 550 nm, a sheet resistance of 7 Ω/sq, and a figure of merit (FOM) of 105 × 10 −3 Ω −1 . These properties are the result of the presence of a discontinuous layer of Ag between two thin layers of TiO 2 . The morphology of a discontinuous layer of Ag nanogranules is confirmed by the observation of a cross-section of a sample with high-resolution transmission electron microscopy (HRTEM) and EDX analyses. Current–voltage diode characteristics of GaAs solar cells measured under standard test illumination at 1000 W/m 2 are analyzed. The formation of an Ohmic contact is explained by the Fermi-level pinning effect caused by nanosized Ag particles in the nanolaminate TiO 2 /Ag/TiO 2 structure. The obtained results demonstrate a new application of oxide−metal−oxide (OMO) coatings as Ohmic contacts to III-V compound semiconductors.

Keywords: transparent Ohmic contact; AlGaAs; solar cells; transparent nanolaminate structure; TiO 2 /Ag/TiO 2; discontinuous Ag layer; Ag nanoparticles; oxide/metal/oxide (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: 2023
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