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Title: 17.5% p-Type Silicon Heterojunction Solar Cells with HWCVD a-Si:H as the Emitter and Back Contact

Abstract

Thin hydrogenated amorphous silicon (a-Si:H) layers deposited by hot-wire chemical vapor deposition (HWCVD) are used as both emitters and back contacts in silicon heterojunction solar cells. Low interface recombination velocity and high open-circuit voltage are achieved by a low substrate temperature (<150 deg C) intrinsic a-Si:H deposition which ensures immediate amorphous silicon deposition. This is followed by deposition of doped a-Si:H at a higher temperature (>200 deg C) which appears to improve dopant activation. With an i/n a-Si:H emitter, we obtain a confirmed efficiency of 17.1% on textured p-type float-zone (FZ) silicon with a screen-printed aluminum back-surface-field (Al-BSF) contact. Employing a-Si:H as both the front emitter and the back contact, we achieve a confirmed efficiency of 17.5%, the highest reported efficiency for a p-type c-Si based heterojunction solar cell.

Authors:
; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
882612
Report Number(s):
NREL/CP-520-38942
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Conference
Resource Relation:
Related Information: Presented at the 2005 DOE Solar Energy Technologies Program Review Meeting held November 7-10, 2005 in Denver, Colorado. Also included in the proceedings available on CD-ROM (DOE/GO-1020060-2245; NREL/CD-520-38577)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; PHOTOVOLTAICS; SOLAR; HETEROJUNCTION SOLAR CELLS; PV; NREL; Solar Energy - Photovoltaics; Silicon Materials and Devices

Citation Formats

Wang, T. H., Page, M. R., Iwaniczko, E., Wang, Q., Xu,Y., Yan, Y., Roybal, L., Levi, D., Bauer, R., Branz, H. M., Yelundur, V., and Rohatgi, A. 17.5% p-Type Silicon Heterojunction Solar Cells with HWCVD a-Si:H as the Emitter and Back Contact. United States: N. p., 2005. Web.
Wang, T. H., Page, M. R., Iwaniczko, E., Wang, Q., Xu,Y., Yan, Y., Roybal, L., Levi, D., Bauer, R., Branz, H. M., Yelundur, V., & Rohatgi, A. 17.5% p-Type Silicon Heterojunction Solar Cells with HWCVD a-Si:H as the Emitter and Back Contact. United States.
Wang, T. H., Page, M. R., Iwaniczko, E., Wang, Q., Xu,Y., Yan, Y., Roybal, L., Levi, D., Bauer, R., Branz, H. M., Yelundur, V., and Rohatgi, A. Tue . "17.5% p-Type Silicon Heterojunction Solar Cells with HWCVD a-Si:H as the Emitter and Back Contact". United States. doi:. https://www.osti.gov/servlets/purl/882612.
@article{osti_882612,
title = {17.5% p-Type Silicon Heterojunction Solar Cells with HWCVD a-Si:H as the Emitter and Back Contact},
author = {Wang, T. H. and Page, M. R. and Iwaniczko, E. and Wang, Q. and Xu,Y. and Yan, Y. and Roybal, L. and Levi, D. and Bauer, R. and Branz, H. M. and Yelundur, V. and Rohatgi, A.},
abstractNote = {Thin hydrogenated amorphous silicon (a-Si:H) layers deposited by hot-wire chemical vapor deposition (HWCVD) are used as both emitters and back contacts in silicon heterojunction solar cells. Low interface recombination velocity and high open-circuit voltage are achieved by a low substrate temperature (<150 deg C) intrinsic a-Si:H deposition which ensures immediate amorphous silicon deposition. This is followed by deposition of doped a-Si:H at a higher temperature (>200 deg C) which appears to improve dopant activation. With an i/n a-Si:H emitter, we obtain a confirmed efficiency of 17.1% on textured p-type float-zone (FZ) silicon with a screen-printed aluminum back-surface-field (Al-BSF) contact. Employing a-Si:H as both the front emitter and the back contact, we achieve a confirmed efficiency of 17.5%, the highest reported efficiency for a p-type c-Si based heterojunction solar cell.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Nov 01 00:00:00 EST 2005},
month = {Tue Nov 01 00:00:00 EST 2005}
}

Conference:
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  • We have developed hydrogenated amorphous silicon (a Si:H) back contacts to both p- and n-type silicon wafers, and employed them in double-heterojunction solar cells. These contacts are deposited entirely at low temperature (<250 C) and replace the standard diffused or alloyed back-surface-field contacts used in single-heterojunction (front-emitter only) cells. High-quality back contacts require excellent surface passivation, indicated by a low surface recombination velocity of minority-carriers (S) or a high open-circuit voltage (Voc). The back contact must also provide good conduction for majority carriers to the external circuit, as indicated by a high light I-V fill factor. We use hot-wire chemicalmore » vapor deposition (HWCVD) to grow a-Si:H layers for both the front emitters and back contacts. Our improved a-Si:H back contacts contribute to our recent achievement of a confirmed 18.2% efficiency in double-heterojunction silicon solar cells on p type textured silicon wafers.« less
  • We have developed hydrogenated amorphous silicon (a-Si:H) back contacts to both p-and n-type silicon wafers, and employed them in double-heterojunction solar cells. These contacts are deposited entirely at low temperature (<250degC) and replace the standard diffused or alloyed back-surface-field contacts used in single-heterojunction (front-emitter only) cells. High-quality back contacts require excellent surface passivation, indicated by a low surface recombination velocity of minority-carriers (S) or a high open-circuit voltage (V{sub oc}). The back contact must also provide good conduction for majority carriers to the external circuit, as indicated by a high light I-V fill factor. We use hot-wire chemical vapor depositionmore » (HWCVD) to grow a-Si:H layers for both the front emitters and back contacts. Our improved a-Si:H back contacts contribute to our recent achievement of a confirmed 18.2% efficiency in double-heterojunction silicon solar cells on p-type textured silicon wafers [1].« less
  • In this paper, two-dimensional (2D) simulation of interdigitated back contact silicon heterojunction (IBC-SHJ) solar cells is presented using Sentaurus Device, a software package of Synopsys TCAD. A model is established incorporating a distribution of trap states of amorphous-silicon material and thermionic emission across the amorphous-silicon / crystalline-silicon heterointerface. The 2D nature of IBC-SHJ device is evaluated and current density-voltage (J-V) curves are generated. Optimization of IBC-SHJ solar cells is then discussed through simulation. It is shown that the open circuit voltage (VOC) and short circuit current density (JSC) of IBC-SHJ solar cells increase with decreasing front surface recombination velocity. Themore » JSC improves further with the increase of relative coverage of p-type emitter contacts, which is explained by the simulated and measured position dependent laser beam induced current (LBIC) line scan. The S-shaped J-V curves with low fill factor (FF) observed in experiments are also simulated, and three methods to improve FF by modifying the intrinsic a-Si buffer layer are suggested: (i) decreased thickness, (ii) increased conductivity, and (iii) reduced band gap. With all these optimizations, an efficiency of 26% for IBC-SHJ solar cells is potentially achievable.« less
  • This paper treats the use of texture etched ZnO:Al films in amorphous silicon solar cells. Chemically textured ZnO:Al films were implemented as a front TCO in p-i-n (superstrate) and n-i-p (substrate) solar cells, and in combination with Ag as a textured back reflector in n-i-p (substrate) solar cells. These cells exhibit excellent optical and light-trapping properties demonstrated by high short-circuit current densities. Adapted microcrystalline p-layers solve the ZnO/p-contact problem and thereby provide high fill factors and open-circuit voltages. The initial efficiencies so far obtained are close to 10% for p-i-n and 8% for n-i-p solar cells.