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Structure-property relations in Ag-Bi-I compounds: Potential Pb-free absorbers in solar cells

Abstract

Ag-Bi-I system attracts much attention recently as emergent materials for absorbers in solar cells. We have investigated single-phase composition regions in Ag2−3xBixI2, analyzed the detailed crystal structures, measured optical and electronic properties, and revealed the structure-property relations. Single-phase samples with the CdCl2-type rhombohedral structures were obtained at the Ag-rich compositions (x = 0.45−0.48), while the defect-spinel-type cubic structure was stabilized at the Bi-rich compositions (x = 0.52−0.57). Both rhombohedral and cubic structures consist of the cubic close-packed I-ion sublattices, and the small difference in the Ag/Bi composition resulted in the distinct crystal structures. Both CdCl2-type rhombohedral and defect-spinel-type cubic compounds exhibited semiconducting natures with proper band gap energies, which indicates that both materials are potentially useful as absorbers in solar cells. The rhombohedral structure compounds have shallower valence band energies, larger indirect band gap energies, and higher electrical conductivity with lower activation energy than the cubic structure compounds. The distinct properties result from the difference in the defect structures, additional Ag occupation in the rhombohedral phase and the deficiencies of the octahedral site in the cubic phase.

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Publication details

The article was received on 22 Nov 2018, accepted on 05 Feb 2019 and first published on 05 Feb 2019


Article type: Paper
DOI: 10.1039/C8TA11227D
Citation: J. Mater. Chem. A, 2019, Accepted Manuscript

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    Structure-property relations in Ag-Bi-I compounds: Potential Pb-free absorbers in solar cells

    A. Koedtruad, M. Goto, M. A. Patino, Z. Tan, H. Guo, T. Nakamura, T. Handa, W. Chen, Y. Chuang, H. Sheu, T. Saito, D. Kan, Y. Kanemitsu, A. Wakamiya and Y. Shimakawa, J. Mater. Chem. A, 2019, Accepted Manuscript , DOI: 10.1039/C8TA11227D

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