Energy-band alignment of II-VI/Zn3P2 heterojunctions from x-ray photoemission spectroscopy

Jeffrey P. Bosco; David O. Scanlon; Graeme W. Watson; Nathan S. Lewis; Harry A. Atwater

doi:10.1063/1.4807646

Energy-band alignment of II-VI/Zn₃P₂ heterojunctions from x-ray photoemission spectroscopy

Jeffrey P. Bosco, David O. Scanlon, Graeme W. Watson, Nathan S. Lewis, Harry A. Atwater

California Institute of Technology

Research output: Contribution to journal › Article › peer-review

21 Citations (Scopus)

Abstract

The energy-band alignments for zb-ZnSe(001)/α-Zn₃P ₂(001), w-CdS(0001)/α-Zn₃P₂(001), and w-ZnO(0001)/α-Zn₃P₂(001) heterojunctions have been determined using high-resolution x-ray photoelectron spectroscopy via the Kraut method. Ab initio hybrid density functional theory calculations of the valence-band density of states were used to determine the energy differences between the core level and valence-band maximum for each of the bulk materials. The ZnSe/Zn₃P₂ heterojunction had a small conduction-band offset, ΔE_C, of -0.03 ± 0.11 eV, demonstrating a nearly ideal energy-band alignment for use in thin-film photovoltaic devices. The CdS/Zn₃P₂ heterojunction was also type-II but had a larger conduction-band offset of ΔE_C = -0.76 ± 0.10 eV. A type-III alignment was observed for the ZnO/Zn₃P₂ heterojunction, with ΔE_C = -1.61 ± 0.16 eV indicating the formation of a tunnel junction at the oxide-phosphide interface. The data also provide insight into the role of the II-VI/Zn₃P₂ band alignment in the reported performance of Zn₃P₂ heterojunction solar cells.

Original language	English
Article number	203705
Journal	Journal of Applied Physics
Volume	113
Issue number	20
DOIs	https://doi.org/10.1063/1.4807646
Publication status	Published - May 28 2013

ASJC Scopus subject areas

Physics and Astronomy(all)

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@article{e05ffdf299f847acaca32d59ac1619d0,

title = "Energy-band alignment of II-VI/Zn3P2 heterojunctions from x-ray photoemission spectroscopy",

abstract = "The energy-band alignments for zb-ZnSe(001)/α-Zn3P 2(001), w-CdS(0001)/α-Zn3P2(001), and w-ZnO(0001)/α-Zn3P2(001) heterojunctions have been determined using high-resolution x-ray photoelectron spectroscopy via the Kraut method. Ab initio hybrid density functional theory calculations of the valence-band density of states were used to determine the energy differences between the core level and valence-band maximum for each of the bulk materials. The ZnSe/Zn3P2 heterojunction had a small conduction-band offset, ΔEC, of -0.03 ± 0.11 eV, demonstrating a nearly ideal energy-band alignment for use in thin-film photovoltaic devices. The CdS/Zn3P2 heterojunction was also type-II but had a larger conduction-band offset of ΔEC = -0.76 ± 0.10 eV. A type-III alignment was observed for the ZnO/Zn3P2 heterojunction, with ΔEC = -1.61 ± 0.16 eV indicating the formation of a tunnel junction at the oxide-phosphide interface. The data also provide insight into the role of the II-VI/Zn3P2 band alignment in the reported performance of Zn3P2 heterojunction solar cells.",

author = "Bosco, {Jeffrey P.} and Scanlon, {David O.} and Watson, {Graeme W.} and Lewis, {Nathan S.} and Atwater, {Harry A.}",

note = "Funding Information: This work was supported by the Dow Chemical Company and by the Department of Energy, Office of Basic Energy Sciences under Grant No. DE-FG02-03ER15483. Computations were performed on the HECToR supercomputer through membership of the HPC Materials Chemistry Consortium under EPSRC (Grant No. EP/F067496), as well as the Kelvin supercomputer as maintained by TCHPC and supported by SFI through the PI programme (Grant Nos. 06/IN.1/I92 and 06/IN.1/I92/EC07). The authors would like to thank Joseph Beardslee for his assistance with the Kratos XPS measurements. J.P.B. acknowledges the NSF for a graduate research fellowship. D.O.S. acknowledges the Ramsay Memorial Trust and University College London for a Ramsay Fellowship.",

year = "2013",

month = may,

day = "28",

doi = "10.1063/1.4807646",

language = "English",

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T1 - Energy-band alignment of II-VI/Zn3P2 heterojunctions from x-ray photoemission spectroscopy

AU - Bosco, Jeffrey P.

AU - Scanlon, David O.

AU - Watson, Graeme W.

AU - Lewis, Nathan S.

AU - Atwater, Harry A.

N1 - Funding Information: This work was supported by the Dow Chemical Company and by the Department of Energy, Office of Basic Energy Sciences under Grant No. DE-FG02-03ER15483. Computations were performed on the HECToR supercomputer through membership of the HPC Materials Chemistry Consortium under EPSRC (Grant No. EP/F067496), as well as the Kelvin supercomputer as maintained by TCHPC and supported by SFI through the PI programme (Grant Nos. 06/IN.1/I92 and 06/IN.1/I92/EC07). The authors would like to thank Joseph Beardslee for his assistance with the Kratos XPS measurements. J.P.B. acknowledges the NSF for a graduate research fellowship. D.O.S. acknowledges the Ramsay Memorial Trust and University College London for a Ramsay Fellowship.

PY - 2013/5/28

Y1 - 2013/5/28

N2 - The energy-band alignments for zb-ZnSe(001)/α-Zn3P 2(001), w-CdS(0001)/α-Zn3P2(001), and w-ZnO(0001)/α-Zn3P2(001) heterojunctions have been determined using high-resolution x-ray photoelectron spectroscopy via the Kraut method. Ab initio hybrid density functional theory calculations of the valence-band density of states were used to determine the energy differences between the core level and valence-band maximum for each of the bulk materials. The ZnSe/Zn3P2 heterojunction had a small conduction-band offset, ΔEC, of -0.03 ± 0.11 eV, demonstrating a nearly ideal energy-band alignment for use in thin-film photovoltaic devices. The CdS/Zn3P2 heterojunction was also type-II but had a larger conduction-band offset of ΔEC = -0.76 ± 0.10 eV. A type-III alignment was observed for the ZnO/Zn3P2 heterojunction, with ΔEC = -1.61 ± 0.16 eV indicating the formation of a tunnel junction at the oxide-phosphide interface. The data also provide insight into the role of the II-VI/Zn3P2 band alignment in the reported performance of Zn3P2 heterojunction solar cells.

AB - The energy-band alignments for zb-ZnSe(001)/α-Zn3P 2(001), w-CdS(0001)/α-Zn3P2(001), and w-ZnO(0001)/α-Zn3P2(001) heterojunctions have been determined using high-resolution x-ray photoelectron spectroscopy via the Kraut method. Ab initio hybrid density functional theory calculations of the valence-band density of states were used to determine the energy differences between the core level and valence-band maximum for each of the bulk materials. The ZnSe/Zn3P2 heterojunction had a small conduction-band offset, ΔEC, of -0.03 ± 0.11 eV, demonstrating a nearly ideal energy-band alignment for use in thin-film photovoltaic devices. The CdS/Zn3P2 heterojunction was also type-II but had a larger conduction-band offset of ΔEC = -0.76 ± 0.10 eV. A type-III alignment was observed for the ZnO/Zn3P2 heterojunction, with ΔEC = -1.61 ± 0.16 eV indicating the formation of a tunnel junction at the oxide-phosphide interface. The data also provide insight into the role of the II-VI/Zn3P2 band alignment in the reported performance of Zn3P2 heterojunction solar cells.

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