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Title: The Effect of Crystallographic Orientation and Nanoscale Surface Morphology on Poly-Si/SiO x Contacts for Silicon Solar Cells

Abstract

High-efficiency crystalline silicon (Si) solar cells require textured surfaces for efficient light trapping. However, passivation of a textured surface to reduce carrier recombination is difficult. Here, we related the electrical properties of cells fabricated on a KOH-etched, random pyramidal textured Si surface to nanostructure of the passivated contact and the textured surface morphology. The effects of both microscopic pyramidal morphology and nanoscale surface roughness on passivated contacts consisting of a polycrystalline Si (poly-Si) deposited on top of an ultrathin, 1.5-2.2 nm, SiOx layer is investigated. Using atomic force microscopy we show a pyramid face, which is predominantly a Si(111) plane to be significantly rougher than a polished Si(111) surface. This roughness results in a nonuniform SiOx layer as determined by transmission electron microscopy (TEM) of a poly-Si/SiOx contact. Our device measurements also show an overall more resistive, and hence thicker SiOx layer over the pyramidal surface as compared to a polished Si(111) surface, which we relate to increased roughness. Using electron-beam-induced current measurements of poly-Si/SiOx contacts we further show that the SiOx layer near the pyramid valleys is preferentially more conducting, and hence likely thinner than over pyramid tips, edges and faces. Hence, both the microscopic pyramidal morphology and nanoscalemore » roughness lead to nonuniform SiOx layer, thus leading to poor poly-Si/SiOx contact passivation. Finally, we report >21% efficient and =80% fill factor front/back poly-Si/SiOx solar cells on both single-side and double-side textured wafers without the use of transparent conductive oxide layers and show that the poorer contact passivation on a textured surface is limited to boron-doped poly-Si/SiOx contacts.« less

Authors:
 [1];  [2]; ORCiD logo [2];  [2];  [2];  [2];  [2];  [2];  [2];  [2];  [2];  [3]
  1. Colorado School of Mines, Golden, CO (United States); National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  3. Colorado School of Mines, Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
OSTI Identifier:
1571392
Report Number(s):
NREL/JA-5900-75083
Journal ID: ISSN 1944-8244
Grant/Contract Number:  
AC36-08GO28308
Resource Type:
Accepted Manuscript
Journal Name:
ACS Applied Materials and Interfaces
Additional Journal Information:
Journal Volume: 11; Journal Issue: 45; Journal ID: ISSN 1944-8244
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; silicon solar cell; passivated contact; silicon oxide; tunneling; surface orientation; electron beam induced current; atomic force microscopy

Citation Formats

Kale, Abhijit, Nemeth, William M., Guthrey, Harvey L., Nanayakkara, Sanjini U., LaSalvia, Vincenzo A., Theingi, San, Findley, Dawn, Page, Matthew, Al-Jassim, Mowafak M., Young, David L., Stradins, Pauls, and Agarwal, Sumit. The Effect of Crystallographic Orientation and Nanoscale Surface Morphology on Poly-Si/SiO x Contacts for Silicon Solar Cells. United States: N. p., 2019. Web. https://doi.org/10.1021/acsami.9b11889.
Kale, Abhijit, Nemeth, William M., Guthrey, Harvey L., Nanayakkara, Sanjini U., LaSalvia, Vincenzo A., Theingi, San, Findley, Dawn, Page, Matthew, Al-Jassim, Mowafak M., Young, David L., Stradins, Pauls, & Agarwal, Sumit. The Effect of Crystallographic Orientation and Nanoscale Surface Morphology on Poly-Si/SiO x Contacts for Silicon Solar Cells. United States. https://doi.org/10.1021/acsami.9b11889
Kale, Abhijit, Nemeth, William M., Guthrey, Harvey L., Nanayakkara, Sanjini U., LaSalvia, Vincenzo A., Theingi, San, Findley, Dawn, Page, Matthew, Al-Jassim, Mowafak M., Young, David L., Stradins, Pauls, and Agarwal, Sumit. Tue . "The Effect of Crystallographic Orientation and Nanoscale Surface Morphology on Poly-Si/SiO x Contacts for Silicon Solar Cells". United States. https://doi.org/10.1021/acsami.9b11889. https://www.osti.gov/servlets/purl/1571392.
@article{osti_1571392,
title = {The Effect of Crystallographic Orientation and Nanoscale Surface Morphology on Poly-Si/SiO x Contacts for Silicon Solar Cells},
author = {Kale, Abhijit and Nemeth, William M. and Guthrey, Harvey L. and Nanayakkara, Sanjini U. and LaSalvia, Vincenzo A. and Theingi, San and Findley, Dawn and Page, Matthew and Al-Jassim, Mowafak M. and Young, David L. and Stradins, Pauls and Agarwal, Sumit},
abstractNote = {High-efficiency crystalline silicon (Si) solar cells require textured surfaces for efficient light trapping. However, passivation of a textured surface to reduce carrier recombination is difficult. Here, we related the electrical properties of cells fabricated on a KOH-etched, random pyramidal textured Si surface to nanostructure of the passivated contact and the textured surface morphology. The effects of both microscopic pyramidal morphology and nanoscale surface roughness on passivated contacts consisting of a polycrystalline Si (poly-Si) deposited on top of an ultrathin, 1.5-2.2 nm, SiOx layer is investigated. Using atomic force microscopy we show a pyramid face, which is predominantly a Si(111) plane to be significantly rougher than a polished Si(111) surface. This roughness results in a nonuniform SiOx layer as determined by transmission electron microscopy (TEM) of a poly-Si/SiOx contact. Our device measurements also show an overall more resistive, and hence thicker SiOx layer over the pyramidal surface as compared to a polished Si(111) surface, which we relate to increased roughness. Using electron-beam-induced current measurements of poly-Si/SiOx contacts we further show that the SiOx layer near the pyramid valleys is preferentially more conducting, and hence likely thinner than over pyramid tips, edges and faces. Hence, both the microscopic pyramidal morphology and nanoscale roughness lead to nonuniform SiOx layer, thus leading to poor poly-Si/SiOx contact passivation. Finally, we report >21% efficient and =80% fill factor front/back poly-Si/SiOx solar cells on both single-side and double-side textured wafers without the use of transparent conductive oxide layers and show that the poorer contact passivation on a textured surface is limited to boron-doped poly-Si/SiOx contacts.},
doi = {10.1021/acsami.9b11889},
journal = {ACS Applied Materials and Interfaces},
number = 45,
volume = 11,
place = {United States},
year = {2019},
month = {10}
}

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Cited by: 3 works
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Figures / Tables:

Figure 1 Figure 1: (a) Schematic of front/back poly-Si/SiOx contact cells on SST and DST n-Cz Si wafers. (b) Cross section SEM image of the front-side of the Al/n + poly-Si/SiOx/n-Si contact stack on a textured Si surface. (c) Current-voltage measurements of the cells shown in “a”. The table in the insetmore » shows their cell parameters.« less

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      Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.