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Title: Back-Contact Crystalline-Silicon Solar Cells and Modules

Abstract

This paper summarizes recent progress in the development of back-contact crystalline-silicon (c-Si) solar cells and modules at Sandia National Laboratories. Back-contact cells have potentially improved efficiencies through the elimination of grid obscuration and allow for significant simplifications in the module assembly process. Optimization of the process sequence has improved the efficiency of our back-contact cell (emitter wrap through) from around 12% to near 17% in the past 12 months. In addition, recent theoretical work has elucidated the device physics of emitter wrap-through cells. Finally, improvements in the assembly processing back-contact cells are described.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
4278
Report Number(s):
SAND99-0591C
TRN: AH200114%%213
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: NCPV Program Review Meeting, Denver, CO (US), 09/08/1999--09/11/1999; Other Information: PBD: 10 Mar 1999
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; EFFICIENCY; OPTIMIZATION; PHYSICS; SANDIA NATIONAL LABORATORIES; SOLAR CELLS

Citation Formats

Bode, M.D., Garrett, S.E., Gee, J.M., Jimeno, J.C., and Smith, D.D. Back-Contact Crystalline-Silicon Solar Cells and Modules. United States: N. p., 1999. Web.
Bode, M.D., Garrett, S.E., Gee, J.M., Jimeno, J.C., & Smith, D.D. Back-Contact Crystalline-Silicon Solar Cells and Modules. United States.
Bode, M.D., Garrett, S.E., Gee, J.M., Jimeno, J.C., and Smith, D.D. Wed . "Back-Contact Crystalline-Silicon Solar Cells and Modules". United States. doi:. https://www.osti.gov/servlets/purl/4278.
@article{osti_4278,
title = {Back-Contact Crystalline-Silicon Solar Cells and Modules},
author = {Bode, M.D. and Garrett, S.E. and Gee, J.M. and Jimeno, J.C. and Smith, D.D.},
abstractNote = {This paper summarizes recent progress in the development of back-contact crystalline-silicon (c-Si) solar cells and modules at Sandia National Laboratories. Back-contact cells have potentially improved efficiencies through the elimination of grid obscuration and allow for significant simplifications in the module assembly process. Optimization of the process sequence has improved the efficiency of our back-contact cell (emitter wrap through) from around 12% to near 17% in the past 12 months. In addition, recent theoretical work has elucidated the device physics of emitter wrap-through cells. Finally, improvements in the assembly processing back-contact cells are described.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Mar 10 00:00:00 EST 1999},
month = {Wed Mar 10 00:00:00 EST 1999}
}

Conference:
Other availability
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  • This paper summarizes recent progress in the development of back-contact crystalline-silicon (c-Si) solar cells and modules at Sandia National Laboratories. Back-contact cells have potentially improved efficiencies through the elimination of grid obscuration and allow for significant simplifications in the module assembly process. Optimization of the process sequence has improved the efficiency of our back-contact cell ({open_quotes}emitter wrap through{close_quotes}) from around 12{percent} to near 17{percent} in the past 12 months. In addition, recent theoretical work has elucidated the device physics of emitter wrap-through cells. Finally, improvements in the assembly process using back-contact cells are described. {copyright} {ital 1999 American Institute ofmore » Physics.}« less
  • The authors are developing new module concepts that encapsulate and electrically connect all the crystalline-silicon (c-Si) photovoltaic (PV) cells in a module in a single step. The new assembly process (1) uses back-contact c-Si cells, (2) uses a module backplane that has both the electrical circuit, encapsulant, and backsheet in a single piece, and (3) uses a single-step process for assembly of these components into a module. This new process reduces module assembly cost by using planar processes that are easy to automate, by reducing the number of steps, and by eliminating low-throughput (e.g., individual cell tabbing, cell stringing, etc.)more » steps. The authors refer to this process as monolithic module assembly since it translates many of the advantages of monolithic module construction of thin-film PV modules to wafered c-Si PV modules. Preliminary development of the new module assembly process, and some estimations of the cost potential of the new process, are presented.« less
  • We study an amorphous/crystalline silicon heterojunction (Si HJ) as a back contact in industrial standard p-type five-inch pseudo-square wafer to replace Al back surface field (BSF) contact. The best efficiency in this study is over 17% with open-circuit (Voc) of 0.623 V, which is very similar to the control cell with Al BSF. We found that Voc has not been improved with the heterojunction structure in the back. The typical minority carrier lifetime of these wafers is on the order of 10 us. We also found that the doping levels of p-layer affect the FF due to conductivity and bandmore » gap shifting, and an optimized layer is identified. We conclude that an amorphous/crystalline silicon heterojunction can be a very promising structure to replace Al BSF back contact.« less
  • Thin hydrogenated amorphous silicon (a-Si:H) layers deposited by hot-wire chemical vapor deposition (HWCVD) are investigated as emitters and back-surface-field (BSF) contacts to make silicon heterojunction solar cells on p-type crystalline silicon wafers. A common requirement for excellent emitter and BSF quality is minimization of interface recombination. Best results require immediate a Si:H deposition and an abrupt and flat interface to the c-Si substrate. We obtain record 16.9% and 14.8% efficiencies on p-type planar float-zone (FZ) and Czochralski (CZ) silicon substrates, respectively, with HWCVD a-Si:H(n) emitters and Al-BSF contacts. Initial efforts with p-type HWCVD Si thin films as the BSF havemore » yielded 12.5% efficiency on p type CZ-Si.« less