TY - JOUR
T1 - Influence of sputtering a ZnMgO window layer on the interface and bulk properties of Cu (In,Ga) Se2 solar cells
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.
N1 - Funding Information:
The authors wish to thank Dr. Ana Kanevce for helping with SCAPS simulation, and Mathew Young and Dr. Sally Asher for SIMS experiments. This work was supported by the U.S. Department of Energy under Contract No. DOE-AC36-08GO28308 with the National Renewable Energy Laboratory.
PY - 2009
Y1 - 2009
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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U2 - 10.1116/1.3256230
DO - 10.1116/1.3256230
M3 - Article
AN - SCOPUS:72849148096
VL - 27
SP - 2384
EP - 2389
JO - Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures
JF - Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures
SN - 1071-1023
IS - 6
ER -