Solar Cell Efficiency and High Temperature Processing of n-type Silicon Grown by the Noncontact Crucible Method
The capital expense (capex) of conventional crystal growth methods is a barrier to sustainable growth of the photovoltaic industry. It is challenging for innovative techniques to displace conventional growth methods due the low dislocation density and high lifetime required for high efficiency devic...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
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Elsevier BV
2018
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| Online Access: | http://hdl.handle.net/1721.1/118849 https://orcid.org/0000-0002-5353-0780 https://orcid.org/0000-0001-9352-8741 https://orcid.org/0000-0002-5559-4286 https://orcid.org/0000-0001-8345-4937 |
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| author | LaSalvia, Vincenzo Morishige, Ashley E. Nakajima, Kazuo Veschetti, Yannick Jay, Frederic Jouini, Anis Stradins, Paul Jensen, Mallory Ann Morishige, Ashley Elizabeth Youssef, Amanda Buonassisi, Anthony |
| author2 | Massachusetts Institute of Technology. Department of Mechanical Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Mechanical Engineering LaSalvia, Vincenzo Morishige, Ashley E. Nakajima, Kazuo Veschetti, Yannick Jay, Frederic Jouini, Anis Stradins, Paul Jensen, Mallory Ann Morishige, Ashley Elizabeth Youssef, Amanda Buonassisi, Anthony |
| author_sort | LaSalvia, Vincenzo |
| collection | MIT |
| description | The capital expense (capex) of conventional crystal growth methods is a barrier to sustainable growth of the photovoltaic industry. It is challenging for innovative techniques to displace conventional growth methods due the low dislocation density and high lifetime required for high efficiency devices. One promising innovation in crystal growth is the noncontact crucible method (NOC-Si), which combines aspects of Czochralski (Cz) and conventional casting. This material has the potential to satisfy the dual requirements, with capex likely between that of Cz (high capex) and multicrystalline silicon (mc-Si, low capex). In this contribution, we observe a strong dependence of solar cell efficiency on ingot height, correlated with the evolution of swirl-like defects, for single crystalline n-type silicon grown by the NOC-Si method. We posit that these defects are similar to those observed in Cz, and we explore the response of NOC-Si to high temperature treatments including phosphorous diffusion gettering (PDG) and Tabula Rasa (TR). The highest lifetimes (2033 μs for the top of the ingot and 342 μs for the bottom of the ingot) are achieved for TR followed by a PDG process comprising a standard plateau and a low temperature anneal. Further improvements can be gained by tailoring the time-temperature profiles of each process. Lifetime analysis after the PDG process indicates the presence of a getterable impurity in the as-grown material, while analysis after TR points to the presence of oxide precipitates especially at the bottom of the ingot. Uniform lifetime degradation is observed after TR which we assign to a presently unknown defect. Future work includes additional TR processing to uncover the nature of this defect, microstructural characterization of suspected oxide precipitates, and optimization of the TR process to achieve the dual goals of high lifetime and spatial homogenization. Keywords: silicon; noncontact crucible; defect; swirl; lifetime; tabula rasa; gettering; capex |
| first_indexed | 2024-09-23T09:15:26Z |
| format | Article |
| id | mit-1721.1/118849 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T09:15:26Z |
| publishDate | 2018 |
| publisher | Elsevier BV |
| record_format | dspace |
| spelling | mit-1721.1/1188492022-09-26T11:09:20Z Solar Cell Efficiency and High Temperature Processing of n-type Silicon Grown by the Noncontact Crucible Method LaSalvia, Vincenzo Morishige, Ashley E. Nakajima, Kazuo Veschetti, Yannick Jay, Frederic Jouini, Anis Stradins, Paul Jensen, Mallory Ann Morishige, Ashley Elizabeth Youssef, Amanda Buonassisi, Anthony Massachusetts Institute of Technology. Department of Mechanical Engineering Jensen, Mallory Ann Morishige, Ashley Elizabeth Youssef, Amanda Buonassisi, Anthony The capital expense (capex) of conventional crystal growth methods is a barrier to sustainable growth of the photovoltaic industry. It is challenging for innovative techniques to displace conventional growth methods due the low dislocation density and high lifetime required for high efficiency devices. One promising innovation in crystal growth is the noncontact crucible method (NOC-Si), which combines aspects of Czochralski (Cz) and conventional casting. This material has the potential to satisfy the dual requirements, with capex likely between that of Cz (high capex) and multicrystalline silicon (mc-Si, low capex). In this contribution, we observe a strong dependence of solar cell efficiency on ingot height, correlated with the evolution of swirl-like defects, for single crystalline n-type silicon grown by the NOC-Si method. We posit that these defects are similar to those observed in Cz, and we explore the response of NOC-Si to high temperature treatments including phosphorous diffusion gettering (PDG) and Tabula Rasa (TR). The highest lifetimes (2033 μs for the top of the ingot and 342 μs for the bottom of the ingot) are achieved for TR followed by a PDG process comprising a standard plateau and a low temperature anneal. Further improvements can be gained by tailoring the time-temperature profiles of each process. Lifetime analysis after the PDG process indicates the presence of a getterable impurity in the as-grown material, while analysis after TR points to the presence of oxide precipitates especially at the bottom of the ingot. Uniform lifetime degradation is observed after TR which we assign to a presently unknown defect. Future work includes additional TR processing to uncover the nature of this defect, microstructural characterization of suspected oxide precipitates, and optimization of the TR process to achieve the dual goals of high lifetime and spatial homogenization. Keywords: silicon; noncontact crucible; defect; swirl; lifetime; tabula rasa; gettering; capex 2018-11-02T18:49:44Z 2018-11-02T18:49:44Z 2016-09 2018-11-02T15:12:22Z Article http://purl.org/eprint/type/JournalArticle 1876-6102 http://hdl.handle.net/1721.1/118849 Jensen, Mallory A. et al. “Solar Cell Efficiency and High Temperature Processing of n-Type Silicon Grown by the Noncontact Crucible Method.” Energy Procedia 92 (August 2016): 815–821 © 2016 The Authors https://orcid.org/0000-0002-5353-0780 https://orcid.org/0000-0001-9352-8741 https://orcid.org/0000-0002-5559-4286 https://orcid.org/0000-0001-8345-4937 http://dx.doi.org/10.1016/J.EGYPRO.2016.07.075 Energy Procedia Creative Commons Attribution-NonCommercial-NoDerivs License http://creativecommons.org/licenses/by-nc-nd/4.0/ application/pdf Elsevier BV Elsevier |
| spellingShingle | LaSalvia, Vincenzo Morishige, Ashley E. Nakajima, Kazuo Veschetti, Yannick Jay, Frederic Jouini, Anis Stradins, Paul Jensen, Mallory Ann Morishige, Ashley Elizabeth Youssef, Amanda Buonassisi, Anthony Solar Cell Efficiency and High Temperature Processing of n-type Silicon Grown by the Noncontact Crucible Method |
| title | Solar Cell Efficiency and High Temperature Processing of n-type Silicon Grown by the Noncontact Crucible Method |
| title_full | Solar Cell Efficiency and High Temperature Processing of n-type Silicon Grown by the Noncontact Crucible Method |
| title_fullStr | Solar Cell Efficiency and High Temperature Processing of n-type Silicon Grown by the Noncontact Crucible Method |
| title_full_unstemmed | Solar Cell Efficiency and High Temperature Processing of n-type Silicon Grown by the Noncontact Crucible Method |
| title_short | Solar Cell Efficiency and High Temperature Processing of n-type Silicon Grown by the Noncontact Crucible Method |
| title_sort | solar cell efficiency and high temperature processing of n type silicon grown by the noncontact crucible method |
| url | http://hdl.handle.net/1721.1/118849 https://orcid.org/0000-0002-5353-0780 https://orcid.org/0000-0001-9352-8741 https://orcid.org/0000-0002-5559-4286 https://orcid.org/0000-0001-8345-4937 |
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