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Title: Silicon Heterojunction Solar Cell Characterization and Optimization Using In Situ and Ex Situ Spectroscopic Ellipsometry: Preprint

Abstract

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-, and 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.

Authors:
; ; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
891543
Report Number(s):
NREL/CP-520-39932
TRN: US200622%%85
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Conference
Resource Relation:
Conference: Presented at 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; 47 OTHER INSTRUMENTATION; ABSORPTION; ALUMINIUM; DEPOSITION; EFFICIENCY; ELLIPSOMETRY; ENERGY CONVERSION; HETEROJUNCTIONS; OPTICAL PROPERTIES; OPTIMIZATION; PROCESSING; SILICON; SOLAR CELLS; SOLAR ENERGY CONVERSION; THICKNESS; THIN FILMS; PV; IN-SITU; EX SITU; SPECTROSCOPIC ELLIPSOMETRY; HETEROJUNCTION; OPTICAL; ELECTRONIC; STRUCTURAL PROPERTIES; DEVICE; Solar Energy - Photovoltaics; Silicon Materials and Devices

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: Preprint. United States: N. p., 2006. Web. doi:10.1109/WCPEC.2006.279828.
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: Preprint. United States. doi:10.1109/WCPEC.2006.279828.
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: Preprint". United States. doi:10.1109/WCPEC.2006.279828. https://www.osti.gov/servlets/purl/891543.
@article{osti_891543,
title = {Silicon Heterojunction Solar Cell Characterization and Optimization Using In Situ and Ex Situ Spectroscopic Ellipsometry: Preprint},
author = {Levi, D. and Iwaniczko, E. and Page, M. and Branz, H. and Wang, T.},
abstractNote = {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-, and 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.},
doi = {10.1109/WCPEC.2006.279828},
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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  • 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.
  • 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
  • Presented at the 2001 NCPV Program Review Meeting: First application of real-time spectroscopic ellipsometry to in situ characterization of hot-wire CVD of hydrogenated-silicon thin films.
  • 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