Influence of Sputtering a ZnMgO Window Layer on the Interface and Bulk Properties of Cu(In,Ga)Se2 Solar Cells

Jian V. Li; Xiaonan Li; Yanfa Yan; Chun Sheng Jiang; Wyatt K. Metzger; Ingrid L. Repins; Miguel A. Contreras; Dean H. Levi

doi:10.1116/1.3256230

Influence of Sputtering a ZnMgO Window Layer on the Interface and Bulk Properties of Cu(In,Ga)Se2 Solar Cells

Jian V. Li, Xiaonan Li, Yanfa Yan, Chun Sheng Jiang, Wyatt K. Metzger, Ingrid L. Repins, Miguel A. Contreras, Dean H. Levi

National Renewable Energy Laboratory

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

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Abstract

The authors studied the influence of sputtering a ZnMgO window layer for Cu (In,Ga) Se₂ solar cells on bulk and interface electrical properties. Admittance spectroscopy reveals deep levels at the ZnMgO/CdS interface whose activation energy (∼0.4 eV) increases with reverse bias, indicating an unpinned quasi-Fermi level at the interface. The Cu (In,Ga) Se₂ carrier concentration determined by capacitance-voltage measurements decreases to 3× 10¹⁴ cm^-3 , compared to 1× 10 ¹⁶ cm^-3 in a device with a ZnO window. Scanning Kelvin probe force microscopy verifies the increased depletion region width and indicates that the junction location is unaltered by ZnMgO. Secondary-ion mass spectroscopy shows the presence of Mg near the top and bottom surfaces of the Cu (In,Ga) Se₂ film. They hypothesize that the decrease in carrier concentration is due to compensation doping of the Cu-poor Cu (In,Ga) Se ₂ by Mg. Optimizing sputtering conditions to reduce surface damage and Mg migration eliminates the interface states and restores the carrier concentration, resulting in device performance comparable to those with a ZnO window.

Original language	American English
Pages (from-to)	2384-2389
Number of pages	6
Journal	Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures
Volume	27
Issue number	6
DOIs	https://doi.org/10.1116/1.3256230 https://doi.org/10.1116/1.3256230
State	Published - 2009

NREL Publication Number

NREL/JA-520-46760

Keywords

carrier density
II-VI semiconductors
magnesium
sputtering
zinc

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Li, J. V., Li, X., Yan, Y., Jiang, C. S., Metzger, W. K., Repins, I. L., Contreras, M. A., & Levi, D. H. (2009). Influence of Sputtering a ZnMgO Window Layer on the Interface and Bulk Properties of Cu(In,Ga)Se2 Solar Cells. Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures, 27(6), 2384-2389. https://doi.org/10.1116/1.3256230, https://doi.org/10.1116/1.3256230

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title = "Influence of Sputtering a ZnMgO Window Layer on the Interface and Bulk Properties of Cu(In,Ga)Se2 Solar Cells",

abstract = "The authors studied the influence of sputtering a ZnMgO window layer for Cu (In,Ga) Se2 solar cells on bulk and interface electrical properties. Admittance spectroscopy reveals deep levels at the ZnMgO/CdS interface whose activation energy (∼0.4 eV) increases with reverse bias, indicating an unpinned quasi-Fermi level at the interface. The Cu (In,Ga) Se2 carrier concentration determined by capacitance-voltage measurements decreases to 3× 1014 cm-3 , compared to 1× 10 16 cm-3 in a device with a ZnO window. Scanning Kelvin probe force microscopy verifies the increased depletion region width and indicates that the junction location is unaltered by ZnMgO. Secondary-ion mass spectroscopy shows the presence of Mg near the top and bottom surfaces of the Cu (In,Ga) Se2 film. They hypothesize that the decrease in carrier concentration is due to compensation doping of the Cu-poor Cu (In,Ga) Se 2 by Mg. Optimizing sputtering conditions to reduce surface damage and Mg migration eliminates the interface states and restores the carrier concentration, resulting in device performance comparable to those with a ZnO window.",

keywords = "carrier density, II-VI semiconductors, magnesium, sputtering, zinc",

author = "Li, {Jian V.} and Xiaonan Li and Yanfa Yan and Jiang, {Chun Sheng} and Metzger, {Wyatt K.} and Repins, {Ingrid L.} and Contreras, {Miguel A.} and Levi, {Dean H.}",

year = "2009",

doi = "10.1116/1.3256230",

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Li, JV, Li, X, Yan, Y, Jiang, CS, Metzger, WK, Repins, IL, Contreras, MA & Levi, DH 2009, 'Influence of Sputtering a ZnMgO Window Layer on the Interface and Bulk Properties of Cu(In,Ga)Se2 Solar Cells', Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures, vol. 27, no. 6, pp. 2384-2389. https://doi.org/10.1116/1.3256230, https://doi.org/10.1116/1.3256230

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AU - Li, Jian V.

AU - Li, Xiaonan

AU - Yan, Yanfa

AU - Jiang, Chun Sheng

AU - Metzger, Wyatt K.

AU - Repins, Ingrid L.

AU - Contreras, Miguel A.

AU - Levi, Dean H.

PY - 2009

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N2 - The authors studied the influence of sputtering a ZnMgO window layer for Cu (In,Ga) Se2 solar cells on bulk and interface electrical properties. Admittance spectroscopy reveals deep levels at the ZnMgO/CdS interface whose activation energy (∼0.4 eV) increases with reverse bias, indicating an unpinned quasi-Fermi level at the interface. The Cu (In,Ga) Se2 carrier concentration determined by capacitance-voltage measurements decreases to 3× 1014 cm-3 , compared to 1× 10 16 cm-3 in a device with a ZnO window. Scanning Kelvin probe force microscopy verifies the increased depletion region width and indicates that the junction location is unaltered by ZnMgO. Secondary-ion mass spectroscopy shows the presence of Mg near the top and bottom surfaces of the Cu (In,Ga) Se2 film. They hypothesize that the decrease in carrier concentration is due to compensation doping of the Cu-poor Cu (In,Ga) Se 2 by Mg. Optimizing sputtering conditions to reduce surface damage and Mg migration eliminates the interface states and restores the carrier concentration, resulting in device performance comparable to those with a ZnO window.

AB - The authors studied the influence of sputtering a ZnMgO window layer for Cu (In,Ga) Se2 solar cells on bulk and interface electrical properties. Admittance spectroscopy reveals deep levels at the ZnMgO/CdS interface whose activation energy (∼0.4 eV) increases with reverse bias, indicating an unpinned quasi-Fermi level at the interface. The Cu (In,Ga) Se2 carrier concentration determined by capacitance-voltage measurements decreases to 3× 1014 cm-3 , compared to 1× 10 16 cm-3 in a device with a ZnO window. Scanning Kelvin probe force microscopy verifies the increased depletion region width and indicates that the junction location is unaltered by ZnMgO. Secondary-ion mass spectroscopy shows the presence of Mg near the top and bottom surfaces of the Cu (In,Ga) Se2 film. They hypothesize that the decrease in carrier concentration is due to compensation doping of the Cu-poor Cu (In,Ga) Se 2 by Mg. Optimizing sputtering conditions to reduce surface damage and Mg migration eliminates the interface states and restores the carrier concentration, resulting in device performance comparable to those with a ZnO window.

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Influence of Sputtering a ZnMgO Window Layer on the Interface and Bulk Properties of Cu(In,Ga)Se2 Solar Cells

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Keywords

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