U.S. Department of Energy Office of Scientific and Technical Information
Large-Area (Ag,Cu)(In,Ga)Se2 Thin-Film Solar Cells with Increased Bandgap and Reduced Voltage Losses Realized with Bulk Defect Reduction and Front-Grading of the Absorber Bandgap
The 1.24 eV bandgap, 18.8% power conversion efficiency Ag-alloyed chalcopyrite (Ag,Cu)(In,Ga)Se2 (ACIGS) solar cells are characterized to relate voltage and efficiency improvements to electro-optical (EO) characteristics. Shockley-Read-Hall recombination center defect density, identified and characterized through deep level transient spectroscopy and time-resolved photoluminescence (TRPL), is reduced through potassium and copper treatment optimization. Concomitantly, longer minority carrier lifetimes are achieved, which increases open-circuit voltage (VOC). Near-conduction band defects associated in earlier studies with light-induced current instability are also mitigated. Analysis of charge-carrier dynamics after single- and two-photon excitation is used to separate recombination at the front interface and in the absorber bulk. From TRPL decay simulations, the authors estimate ranges of key solar cell material characteristics: bulk carrier lifetime Tbulk = 110-210 ns, charge-carrier mobility u = 110-160 cm2 V-1 s-1, and front interface recombination velocity Sfront = 700-1050 cm s-1. This lowest-reported Sfront for ACIGS absorbers originates from the notched conduction band grading, which also makes the impact of the back interface recombination negligible. It is suggested in the results that solar cell performance enhancements can be made most readily with two distinct strategies: improving device architecture and reducing semiconductor defect densities. Using these approaches, power conversion efficiency in large-area solar cells is improved by 1.1% absolute.
Bothwell, Alexandra M., et al. "Large-Area (Ag,Cu)(In,Ga)Se<sub>2</sub> Thin-Film Solar Cells with Increased Bandgap and Reduced Voltage Losses Realized with Bulk Defect Reduction and Front-Grading of the Absorber Bandgap." Solar RRL, vol. 6, no. 8, Apr. 2022. https://doi.org/10.1002/solr.202200230
Bothwell, Alexandra M., Li, Siming, Farshchi, Rouin, Miller, Michael F., Wands, Jake, Perkins, Craig L., Rockett, Angus, Arehart, Aaron R., & Kuciauskas, Darius (2022). Large-Area (Ag,Cu)(In,Ga)Se<sub>2</sub> Thin-Film Solar Cells with Increased Bandgap and Reduced Voltage Losses Realized with Bulk Defect Reduction and Front-Grading of the Absorber Bandgap. Solar RRL, 6(8). https://doi.org/10.1002/solr.202200230
Bothwell, Alexandra M., Li, Siming, Farshchi, Rouin, et al., "Large-Area (Ag,Cu)(In,Ga)Se<sub>2</sub> Thin-Film Solar Cells with Increased Bandgap and Reduced Voltage Losses Realized with Bulk Defect Reduction and Front-Grading of the Absorber Bandgap," Solar RRL 6, no. 8 (2022), https://doi.org/10.1002/solr.202200230
@article{osti_1869796,
author = {Bothwell, Alexandra M. and Li, Siming and Farshchi, Rouin and Miller, Michael F. and Wands, Jake and Perkins, Craig L. and Rockett, Angus and Arehart, Aaron R. and Kuciauskas, Darius},
title = {Large-Area (Ag,Cu)(In,Ga)Se<sub>2</sub> Thin-Film Solar Cells with Increased Bandgap and Reduced Voltage Losses Realized with Bulk Defect Reduction and Front-Grading of the Absorber Bandgap},
annote = {The 1.24 eV bandgap, 18.8% power conversion efficiency Ag-alloyed chalcopyrite (Ag,Cu)(In,Ga)Se2 (ACIGS) solar cells are characterized to relate voltage and efficiency improvements to electro-optical (EO) characteristics. Shockley-Read-Hall recombination center defect density, identified and characterized through deep level transient spectroscopy and time-resolved photoluminescence (TRPL), is reduced through potassium and copper treatment optimization. Concomitantly, longer minority carrier lifetimes are achieved, which increases open-circuit voltage (VOC). Near-conduction band defects associated in earlier studies with light-induced current instability are also mitigated. Analysis of charge-carrier dynamics after single- and two-photon excitation is used to separate recombination at the front interface and in the absorber bulk. From TRPL decay simulations, the authors estimate ranges of key solar cell material characteristics: bulk carrier lifetime Tbulk = 110-210 ns, charge-carrier mobility u = 110-160 cm2 V-1 s-1, and front interface recombination velocity Sfront = 700-1050 cm s-1. This lowest-reported Sfront for ACIGS absorbers originates from the notched conduction band grading, which also makes the impact of the back interface recombination negligible. It is suggested in the results that solar cell performance enhancements can be made most readily with two distinct strategies: improving device architecture and reducing semiconductor defect densities. Using these approaches, power conversion efficiency in large-area solar cells is improved by 1.1% absolute.},
doi = {10.1002/solr.202200230},
url = {https://www.osti.gov/biblio/1869796},
journal = {Solar RRL},
issn = {ISSN 2367-198X},
number = {8},
volume = {6},
place = {United States},
publisher = {Wiley},
year = {2022},
month = {04}}