Morphological–Electrical Property Relation in Cu(In,Ga)(S,Se)2 Solar Cells: Significance of Crystal Grain Growth and Band Grading by Potassium Treatment

Joo Hyun Kim; Min Kyu Kim; Abay Gadisa; Samuel J. Stuard; Masrur Morshed Nahid; Soyeong Kwon; Soohyun Bae; Byoungwoo Kim; Gi Soon Park; Da Hye Won; Dong Ki Lee; Dong Wook Kim; Tae Joo Shin; Young Rag Do; Jihyun Kim; Won Jun Choi; Harald Ade; Byoung Koun Min

doi:10.1002/smll.202003865

Morphological–Electrical Property Relation in Cu(In,Ga)(S,Se)₂ Solar Cells: Significance of Crystal Grain Growth and Band Grading by Potassium Treatment

Joo Hyun Kim, Min Kyu Kim, Abay Gadisa, Samuel J. Stuard, Masrur Morshed Nahid, Soyeong Kwon, Soohyun Bae, Byoungwoo Kim, Gi Soon Park, Da Hye Won, Dong Ki Lee, Dong Wook Kim, Tae Joo Shin, Young Rag Do, Jihyun Kim, Won Jun Choi, Harald Ade, Byoung Koun Min

Department of Chemical and Biological Engineering

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

12 Citations (Scopus)

Abstract

Solution-processed Cu(In,Ga)(S,Se)₂ (CIGS) has a great potential for the production of large-area photovoltaic devices at low cost. However, CIGS solar cells processed from solution exhibit relatively lower performance compared to vacuum-processed devices because of a lack of proper composition distribution, which is mainly instigated by the limited Se uptake during chalcogenization. In this work, a unique potassium treatment method is utilized to improve the selenium uptake judiciously, enhancing grain sizes and forming a wider bandgap minimum region. Careful engineering of the bandgap grading structure also results in an enlarged space charge region, which is favorable for electron–hole separation and efficient charge carrier collection. Besides, this device processing approach has led to a linearly increasing electron diffusion length and carrier lifetime with increasing the grain size of the CIGS film, which is a critical achievement for enhancing photocurrent yield. Overall, 15% of power conversion efficiency is achieved in solar cells processed from environmentally benign solutions. This approach offers critical insights for precise device design and processing rules for solution-processed CIGS solar cells.

Original language	English
Article number	2003865
Journal	Small
Volume	16
Issue number	48
DOIs	https://doi.org/10.1002/smll.202003865
Publication status	Published - 2020 Dec 3

Bibliographical note

Funding Information:
J.‐H.K. and M.K.K. contributed equally to this work. This work was supported by the Energy Technology Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant (no. 20163010012570) funded by the Korean Government. This work was also partially supported by the KU‐KIST Graduate School Project. Work of H.A. and M.M.N. of NCSU was supported by the Research Opportunity Initiative grant for UNC General Administration and S.J.S. was supported by the National Science Foundation (no. DGE‐1633587). Hard X‐ray GI‐WAXS and soft X‐ray SAXS data were acquired at beamline 6D in PAL (supported in part by Ministry of Science and ICT, no. NRF‐2018R1A5A 1025224) and beamline 11.0.1.2 in the ALS at LBNL (supported by the U.S. Department of Energy, no. DE‐AC02‐05CH11231), respectively. Cheng Wang is acknowledged for help with X‐ray experimental setup and maintenance of the beamline at 11.0.1.2. The authors also acknowledge Dr. Ji‐Young Kim in the Advanced Analysis Center at KIST for assisting EBIC measurement.

Funding Information:
J.-H.K. and M.K.K. contributed equally to this work. This work was supported by the Energy Technology Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant (no. 20163010012570) funded by the Korean Government. This work was also partially supported by the KU-KIST Graduate School Project. Work of H.A. and M.M.N. of NCSU was supported by the Research Opportunity Initiative grant for UNC General Administration and S.J.S. was supported by the National Science Foundation (no. DGE-1633587). Hard X-ray GI-WAXS and soft X-ray SAXS data were acquired at beamline 6D in PAL (supported in part by Ministry of Science and ICT, no. NRF-2018R1A5A 1025224) and beamline 11.0.1.2 in the ALS at LBNL (supported by the U.S. Department of Energy, no. DE-AC02-05CH11231), respectively. Cheng Wang is acknowledged for help with X-ray experimental setup and maintenance of the beamline at 11.0.1.2. The authors also acknowledge Dr. Ji-Young Kim in the Advanced Analysis Center at KIST for assisting EBIC measurement.

Publisher Copyright:
© 2020 Wiley-VCH GmbH

Keywords

CIGS solar cell
average domain spacing
band grading
electron diffusion length
solution process

ASJC Scopus subject areas

Engineering (miscellaneous)
Chemistry(all)
Materials Science(all)
Biotechnology
Biomaterials

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1002/smll.202003865

Cite this

Kim, J. H., Kim, M. K., Gadisa, A., Stuard, S. J., Nahid, M. M., Kwon, S., Bae, S., Kim, B., Park, G. S., Won, D. H., Lee, D. K., Kim, D. W., Shin, T. J., Do, Y. R., Kim, J., Choi, W. J., Ade, H., & Min, B. K. (2020). Morphological–Electrical Property Relation in Cu(In,Ga)(S,Se)₂ Solar Cells: Significance of Crystal Grain Growth and Band Grading by Potassium Treatment. Small, 16(48), Article 2003865. https://doi.org/10.1002/smll.202003865

Kim, JH, Kim, MK, Gadisa, A, Stuard, SJ, Nahid, MM, Kwon, S, Bae, S, Kim, B, Park, GS, Won, DH, Lee, DK, Kim, DW, Shin, TJ, Do, YR, Kim, J, Choi, WJ, Ade, H & Min, BK 2020, 'Morphological–Electrical Property Relation in Cu(In,Ga)(S,Se)₂ Solar Cells: Significance of Crystal Grain Growth and Band Grading by Potassium Treatment', Small, vol. 16, no. 48, 2003865. https://doi.org/10.1002/smll.202003865

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title = "Morphological–Electrical Property Relation in Cu(In,Ga)(S,Se)2 Solar Cells: Significance of Crystal Grain Growth and Band Grading by Potassium Treatment",

abstract = "Solution-processed Cu(In,Ga)(S,Se)2 (CIGS) has a great potential for the production of large-area photovoltaic devices at low cost. However, CIGS solar cells processed from solution exhibit relatively lower performance compared to vacuum-processed devices because of a lack of proper composition distribution, which is mainly instigated by the limited Se uptake during chalcogenization. In this work, a unique potassium treatment method is utilized to improve the selenium uptake judiciously, enhancing grain sizes and forming a wider bandgap minimum region. Careful engineering of the bandgap grading structure also results in an enlarged space charge region, which is favorable for electron–hole separation and efficient charge carrier collection. Besides, this device processing approach has led to a linearly increasing electron diffusion length and carrier lifetime with increasing the grain size of the CIGS film, which is a critical achievement for enhancing photocurrent yield. Overall, 15% of power conversion efficiency is achieved in solar cells processed from environmentally benign solutions. This approach offers critical insights for precise device design and processing rules for solution-processed CIGS solar cells.",

keywords = "CIGS solar cell, average domain spacing, band grading, electron diffusion length, solution process",

author = "Kim, {Joo Hyun} and Kim, {Min Kyu} and Abay Gadisa and Stuard, {Samuel J.} and Nahid, {Masrur Morshed} and Soyeong Kwon and Soohyun Bae and Byoungwoo Kim and Park, {Gi Soon} and Won, {Da Hye} and Lee, {Dong Ki} and Kim, {Dong Wook} and Shin, {Tae Joo} and Do, {Young Rag} and Jihyun Kim and Choi, {Won Jun} and Harald Ade and Min, {Byoung Koun}",

note = "Funding Information: J.‐H.K. and M.K.K. contributed equally to this work. This work was supported by the Energy Technology Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant (no. 20163010012570) funded by the Korean Government. This work was also partially supported by the KU‐KIST Graduate School Project. Work of H.A. and M.M.N. of NCSU was supported by the Research Opportunity Initiative grant for UNC General Administration and S.J.S. was supported by the National Science Foundation (no. DGE‐1633587). Hard X‐ray GI‐WAXS and soft X‐ray SAXS data were acquired at beamline 6D in PAL (supported in part by Ministry of Science and ICT, no. NRF‐2018R1A5A 1025224) and beamline 11.0.1.2 in the ALS at LBNL (supported by the U.S. Department of Energy, no. DE‐AC02‐05CH11231), respectively. Cheng Wang is acknowledged for help with X‐ray experimental setup and maintenance of the beamline at 11.0.1.2. The authors also acknowledge Dr. Ji‐Young Kim in the Advanced Analysis Center at KIST for assisting EBIC measurement. Funding Information: J.-H.K. and M.K.K. contributed equally to this work. This work was supported by the Energy Technology Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant (no. 20163010012570) funded by the Korean Government. This work was also partially supported by the KU-KIST Graduate School Project. Work of H.A. and M.M.N. of NCSU was supported by the Research Opportunity Initiative grant for UNC General Administration and S.J.S. was supported by the National Science Foundation (no. DGE-1633587). Hard X-ray GI-WAXS and soft X-ray SAXS data were acquired at beamline 6D in PAL (supported in part by Ministry of Science and ICT, no. NRF-2018R1A5A 1025224) and beamline 11.0.1.2 in the ALS at LBNL (supported by the U.S. Department of Energy, no. DE-AC02-05CH11231), respectively. Cheng Wang is acknowledged for help with X-ray experimental setup and maintenance of the beamline at 11.0.1.2. The authors also acknowledge Dr. Ji-Young Kim in the Advanced Analysis Center at KIST for assisting EBIC measurement. Publisher Copyright: {\textcopyright} 2020 Wiley-VCH GmbH",

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month = dec,

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doi = "10.1002/smll.202003865",

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T2 - Significance of Crystal Grain Growth and Band Grading by Potassium Treatment

AU - Kim, Joo Hyun

AU - Kim, Min Kyu

AU - Gadisa, Abay

AU - Stuard, Samuel J.

AU - Nahid, Masrur Morshed

AU - Kwon, Soyeong

AU - Bae, Soohyun

AU - Kim, Byoungwoo

AU - Park, Gi Soon

AU - Won, Da Hye

AU - Lee, Dong Ki

AU - Kim, Dong Wook

AU - Shin, Tae Joo

AU - Do, Young Rag

AU - Kim, Jihyun

AU - Choi, Won Jun

AU - Ade, Harald

AU - Min, Byoung Koun

N1 - Funding Information: J.‐H.K. and M.K.K. contributed equally to this work. This work was supported by the Energy Technology Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant (no. 20163010012570) funded by the Korean Government. This work was also partially supported by the KU‐KIST Graduate School Project. Work of H.A. and M.M.N. of NCSU was supported by the Research Opportunity Initiative grant for UNC General Administration and S.J.S. was supported by the National Science Foundation (no. DGE‐1633587). Hard X‐ray GI‐WAXS and soft X‐ray SAXS data were acquired at beamline 6D in PAL (supported in part by Ministry of Science and ICT, no. NRF‐2018R1A5A 1025224) and beamline 11.0.1.2 in the ALS at LBNL (supported by the U.S. Department of Energy, no. DE‐AC02‐05CH11231), respectively. Cheng Wang is acknowledged for help with X‐ray experimental setup and maintenance of the beamline at 11.0.1.2. The authors also acknowledge Dr. Ji‐Young Kim in the Advanced Analysis Center at KIST for assisting EBIC measurement. Funding Information: J.-H.K. and M.K.K. contributed equally to this work. This work was supported by the Energy Technology Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant (no. 20163010012570) funded by the Korean Government. This work was also partially supported by the KU-KIST Graduate School Project. Work of H.A. and M.M.N. of NCSU was supported by the Research Opportunity Initiative grant for UNC General Administration and S.J.S. was supported by the National Science Foundation (no. DGE-1633587). Hard X-ray GI-WAXS and soft X-ray SAXS data were acquired at beamline 6D in PAL (supported in part by Ministry of Science and ICT, no. NRF-2018R1A5A 1025224) and beamline 11.0.1.2 in the ALS at LBNL (supported by the U.S. Department of Energy, no. DE-AC02-05CH11231), respectively. Cheng Wang is acknowledged for help with X-ray experimental setup and maintenance of the beamline at 11.0.1.2. The authors also acknowledge Dr. Ji-Young Kim in the Advanced Analysis Center at KIST for assisting EBIC measurement. Publisher Copyright: © 2020 Wiley-VCH GmbH

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N2 - Solution-processed Cu(In,Ga)(S,Se)2 (CIGS) has a great potential for the production of large-area photovoltaic devices at low cost. However, CIGS solar cells processed from solution exhibit relatively lower performance compared to vacuum-processed devices because of a lack of proper composition distribution, which is mainly instigated by the limited Se uptake during chalcogenization. In this work, a unique potassium treatment method is utilized to improve the selenium uptake judiciously, enhancing grain sizes and forming a wider bandgap minimum region. Careful engineering of the bandgap grading structure also results in an enlarged space charge region, which is favorable for electron–hole separation and efficient charge carrier collection. Besides, this device processing approach has led to a linearly increasing electron diffusion length and carrier lifetime with increasing the grain size of the CIGS film, which is a critical achievement for enhancing photocurrent yield. Overall, 15% of power conversion efficiency is achieved in solar cells processed from environmentally benign solutions. This approach offers critical insights for precise device design and processing rules for solution-processed CIGS solar cells.

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