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Title: Silicon Heterojunction Solar Cell Characterization and Optimization Using In Situ and Ex Situ Spectroscopic Ellipsometry (Presentation)

Abstract

The summary of this report is that: in situ SE gives insight into growth mechanisms and accurate layer thickness; (2) ex situ SE measures completed device structures to determine integrated optical properties; and (3) the combination of in situ and ex situ SE provides a powerful method for pinpointing the effects of processing changes in actual SHJ devices and guiding optimization.

Authors:
; ; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
894451
Report Number(s):
NREL/PR-520-39986
TRN: US200701%%463
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Conference
Resource Relation:
Conference: Prepared for the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion (WCPEC-4), 7-12 May 2006, Waikoloa, Hawaii
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; ELLIPSOMETRY; ENERGY CONVERSION; HETEROJUNCTIONS; OPTICAL PROPERTIES; OPTIMIZATION; PROCESSING; SILICON; SOLAR CELLS; THICKNESS; SPECTROSCOPY; PHOTOVOLTAIC; PV; SILICON HETEROJUNCTION SOLAR CELL; SPECTROSCOPIC ELLIPSOMETRY; HOT-WIRED CVD; IN SITU; EX SITU; SOLAR ENERGY; NREL; Solar Energy - Photovoltaics

Citation Formats

Levi, D., Iwaniczko, E., Page, M., Branz, H., and Wang T. Silicon Heterojunction Solar Cell Characterization and Optimization Using In Situ and Ex Situ Spectroscopic Ellipsometry (Presentation). United States: N. p., 2006. Web.
Levi, D., Iwaniczko, E., Page, M., Branz, H., & Wang T. Silicon Heterojunction Solar Cell Characterization and Optimization Using In Situ and Ex Situ Spectroscopic Ellipsometry (Presentation). United States.
Levi, D., Iwaniczko, E., Page, M., Branz, H., and Wang T. Mon . "Silicon Heterojunction Solar Cell Characterization and Optimization Using In Situ and Ex Situ Spectroscopic Ellipsometry (Presentation)". United States. doi:. https://www.osti.gov/servlets/purl/894451.
@article{osti_894451,
title = {Silicon Heterojunction Solar Cell Characterization and Optimization Using In Situ and Ex Situ Spectroscopic Ellipsometry (Presentation)},
author = {Levi, D. and Iwaniczko, E. and Page, M. and Branz, H. and Wang T.},
abstractNote = {The summary of this report is that: in situ SE gives insight into growth mechanisms and accurate layer thickness; (2) ex situ SE measures completed device structures to determine integrated optical properties; and (3) the combination of in situ and ex situ SE provides a powerful method for pinpointing the effects of processing changes in actual SHJ devices and guiding optimization.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2006},
month = {Mon May 01 00:00:00 EDT 2006}
}

Conference:
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  • We use in-situ and ex-situ spectroscopic ellipsometry to characterize the optical, electronic, and structural properties of individual layers and completed silicon heterojunction devices. The combination of in-situ measurements during thin film deposition with ex-situ measurements of completed devices allows us to understand both the growth dynamics of the materials and the effects of each processing step on material properties. In-situ ellipsometry measurements enable us to map out how the optical properties change with deposition conditions, pointing the way towards reducing the absorption loss and increasing device efficiency. We use the measured optical properties and thickness of the i-, n-, andmore » p-layers in optical device modeling to determine how the material properties affect device performance. Our best solar energy conversion efficiencies are 16.9% for a non-textured, single-sided device with an aluminum back surface field contact on a p-type float zone silicon wafer, and 17.8% for a textured double-sided device on a p-type float zone silicon wafer.« less
  • We use in-situ and ex-situ spectroscopic ellipsometry to characterize the optical, electronic, and structural properties of individual layers and completed silicon heterojunction devices. The combination of in-situ measurements during thin film deposition with ex-situ measurements of completed devices allows us to understand both the growth dynamics of the materials and the effects of each processing step on material properties. In-situ ellipsometry measurements enable us to map out how the optical properties change with deposition conditions, pointing the way towards reducing the absorption loss and increasing device efficiency. We use the measured optical properties and thickness of the i-, n-, andmore » p-layers in optical device modeling to determine how the material properties affect device performance. Our best solar energy conversion efficiencies are 16.9% for a non-textured, single-sided device with an aluminum back surface field contact on a p-type float zone silicon wafer, and 17.8% for a textured double-sided device on a p-type float zone silicon wafer.« less
  • We have used hot wire chemical vapor deposition (HWCVD) to fabricate silicon heterojunction (SHJ) solar cells on p-type FZ silicon substrates with efficiencies as high as 18.2%. The best cells are deposited on anisotropically-textured (100) silicon substrates where an etching process creates pyramidal facets with (111) crystal faces. Texturing increases J{sub sc} through enhanced light trapping, yet our highest V{sub oc} devices are deposited on un-textured (100) substrates. One of the key factors in maximizing the efficiency of our SHJ devices is the process of optimization of the material properties of the 3-5 nm thick hydrogenated amorphous silicon (a-Si:H) layersmore » used to create the junction and back contact in these cells. Such optimization is technically challenging because of the difficulty in measuring the properties of extremely thin layers. In this study, we have utilized spectroscopic ellipsometry (SE) and photoconductivity decay to conclude that a-Si:H films grown on (111) substrates are substantially similar to films grown on (100) substrates. In addition, analysis of the substrate temperature dependence of surface roughness evolution reveals a substrate-independent mechanism of surface smoothening with an activation energy of 0.28 eV. Analysis of the substrate temperature dependence of surface passivation reveals a passivation mechanism with an activation energy of 0.63 eV.« less
  • Real-time, in-situ characterization of hot-wire chemical vapor deposition (HWCVD) growth of hydrogenated silicon (Si:H) thin films offers unique insight into the properties of the materials and mechanisms of their growth. We have used in-situ spectroscopic ellipsometry to characterize Si:H crystallinity as a function of film thickness and deposition conditions. We find that the transition from amorphous to microcrystalline growth is a strong function of film thickness and hydrogen dilution, and a weak function of substrate temperature. We have expressed this information in terms of a color-coded phase-space map of the amorphous to microcrystalline transition in HWCVD growth on crystalline Simore » substrates.« less
  • This conference paper provides a brief look at the current U.S. research and development (R&D) investments in photovoltaics, covering the spectrum from materials and devices through electronics and systems reliability. The program is balanced among fundamental R&D, technology development, and systems performance and reliability, with more than half the funding for university and industry partners. The major activities can be categorized into two general areas: improving current and near-term technologies toward their expected performance levels (the largest portion), and positioning the United States for technical leadership, decision making, and ownership for the host of next-technology options (including some options thatmore » have been called third-generation). The investments in these higher risk, longer-term technology generations provide options that could leapfrog into more rapid use because of their promise of potentially high payoff. Solar electricity is part of America's present and future energy security and independence-as is the R&D that enables it.« less