Modifications of Textured Silicon Surface Morphology and Its Effect on Poly-Si/SiO x Contact Passivation for Silicon Solar Cells

Kale, Abhijit; Nemeth, William M; Guthrey, Harvey L; Page, Matthew; Al-Jassim, Mowafak M; Young, David L; Agarwal, Sumit; Stradins, Pauls

doi:10.1109/JPHOTOV.2019.2937230

Title: Modifications of Textured Silicon Surface Morphology and Its Effect on Poly-Si/SiO _x Contact Passivation for Silicon Solar Cells

Full Record
Other Related Research

Abstract

High-efficiency crystalline silicon (c -Si) solar cells require textured surfaces for efficient light trapping. However, passivation of a textured pyramidal surface to reduce carrier recombination is challenging due to the presence of sharp tips, edges, and valleys. Using electrical and surface microscopies combined with lifetime measurements, we report on the effect of HF:HNO3 etching on the pyramidal textured Si surface morphology, and on poly-Si/SiOx contact performance. Preferential rounding of either the valleys between pyramids, or the pyramid tips is obtained depending on the HF:HNO3 solution temperature. Both these morphologies make the pyramid shape irregular, with the pyramid faces no longer being predominantly a Si(111) surface. Our atomic force microscopy measurements further show that the nanoscale roughness over the pyramid face also reduces after HF:HNO3 etching. Thus, etching affects the microscopic pyramidal shape, the dominant crystallographic orientation, and the nanoscale roughness of the surface. We speculate that these three surface effects result in the improvement of surface passivation via poly-Si/SiOx contacts. However, this improved passivation is accompanied by increased reflectance of the HF:HNO3-etched textured surface. Finally, our electron-beam-induced current measurements reveal thickness nonuniformities in the thermally grown SiOx layer on the HF:HNO3-etched textured Si surface: SiO x is thicker near themore »« less

Authors:

Kale, Abhijit ^[1]; Nemeth, William M ^[2];

^[2]; Page, Matthew ^[2]; Al-Jassim, Mowafak M ^[2]; Young, David L ^[2]; Agarwal, Sumit ^[2]; Stradins, Pauls ^[2]

National Renewable Energy Laboratory (NREL), Golden, CO (United States); Colorado School of Mines, Golden, CO (United States)
National Renewable Energy Laboratory (NREL), Golden, CO (United States)

Publication Date:: Fri Nov 01 00:00:00 EDT 2019

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:: 1573202

Report Number(s):: NREL/JA-5900-74648
Journal ID: ISSN 2156-3381

Grant/Contract Number:: AC36-08GO28308

Resource Type:: Accepted Manuscript

Journal Name:: IEEE Journal of Photovoltaics

Additional Journal Information:: Journal Volume: 9; Journal Issue: 6; Journal ID: ISSN 2156-3381

Publisher:: IEEE

Country of Publication:: United States

Language:: English

Subject:: 14 SOLAR ENERGY; 36 MATERIALS SCIENCE; atomic force microscopy; electron beam induced current; passivated contact; pyramid rounding; silicon solar cell

Citation Formats


                    Kale, Abhijit, Nemeth, William M, Guthrey, Harvey L, Page, Matthew, Al-Jassim, Mowafak M, Young, David L, Agarwal, Sumit, and Stradins, Pauls. Modifications of Textured Silicon Surface Morphology and Its Effect on Poly-Si/SiO x Contact Passivation for Silicon Solar Cells.  United States: N. p., 2019. 
Web.  doi:10.1109/JPHOTOV.2019.2937230.

Copy to clipboard


                    Kale, Abhijit, Nemeth, William M, Guthrey, Harvey L, Page, Matthew, Al-Jassim, Mowafak M, Young, David L, Agarwal, Sumit, & Stradins, Pauls. Modifications of Textured Silicon Surface Morphology and Its Effect on Poly-Si/SiO x Contact Passivation for Silicon Solar Cells.  United States.  https://doi.org/10.1109/JPHOTOV.2019.2937230

Copy to clipboard


                    Kale, Abhijit, Nemeth, William M, Guthrey, Harvey L, Page, Matthew, Al-Jassim, Mowafak M, Young, David L, Agarwal, Sumit, and Stradins, Pauls. Fri .  
"Modifications of Textured Silicon Surface Morphology and Its Effect on Poly-Si/SiO x Contact Passivation for Silicon Solar Cells".  United States.  https://doi.org/10.1109/JPHOTOV.2019.2937230.  https://www.osti.gov/servlets/purl/1573202.

Copy to clipboard


                    
@article{osti_1573202,

  title        = {Modifications of Textured Silicon Surface Morphology and Its Effect on Poly-Si/SiO x Contact Passivation for Silicon Solar Cells},

  author       = {Kale, Abhijit and Nemeth, William M and Guthrey, Harvey L and Page, Matthew and Al-Jassim, Mowafak M and Young, David L and Agarwal, Sumit and Stradins, Pauls},

  abstractNote = {High-efficiency crystalline silicon (c -Si) solar cells require textured surfaces for efficient light trapping. However, passivation of a textured pyramidal surface to reduce carrier recombination is challenging due to the presence of sharp tips, edges, and valleys. Using electrical and surface microscopies combined with lifetime measurements, we report on the effect of HF:HNO3 etching on the pyramidal textured Si surface morphology, and on poly-Si/SiOx contact performance. Preferential rounding of either the valleys between pyramids, or the pyramid tips is obtained depending on the HF:HNO3 solution temperature. Both these morphologies make the pyramid shape irregular, with the pyramid faces no longer being predominantly a Si(111) surface. Our atomic force microscopy measurements further show that the nanoscale roughness over the pyramid face also reduces after HF:HNO3 etching. Thus, etching affects the microscopic pyramidal shape, the dominant crystallographic orientation, and the nanoscale roughness of the surface. We speculate that these three surface effects result in the improvement of surface passivation via poly-Si/SiOx contacts. However, this improved passivation is accompanied by increased reflectance of the HF:HNO3-etched textured surface. Finally, our electron-beam-induced current measurements reveal thickness nonuniformities in the thermally grown SiOx layer on the HF:HNO3-etched textured Si surface: SiO x is thicker near the pyramid tips, edges, and faces as compared with near the valleys between pyramids. This nonuniformity in the SiOx layer may explain the poorer passivation obtained on a KOH-textured and HF:HNO3-etched textured surface as compared with a planar surface.},

  doi          = {10.1109/JPHOTOV.2019.2937230},

  journal      = {IEEE Journal of Photovoltaics},

  number       = 6,

  volume       = 9,

  place        = {United States},

  year         = {Fri Nov 01 00:00:00 EDT 2019},

  month        = {Fri Nov 01 00:00:00 EDT 2019}

}

Copy to clipboard

Journal Article:

Free Publicly Available Full Text

Accepted Manuscript (DOE)

Publisher's Version of Record

https://doi.org/10.1109/JPHOTOV.2019.2937230

Other availability

Search WorldCat to find libraries that may hold this journal

Citation Metrics:

Cited by: 9 works

Citation information provided by
Web of Science

Save / Share:

Export Metadata

Save to My Library

Similar Records in DOE PAGES and OSTI.GOV collections:

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

Journal Article Kale, Abhijit ; Nemeth, William M. ; Guthrey, Harvey L. ; ... - ACS Applied Materials and Interfaces

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, SiO_x layer is investigated. Using atomic force microscopy we show a pyramid face, which is predominantly a Si(111) planemore »« less
Cited by 16
https://doi.org/10.1021/acsami.9b11889

Full Text Available
Effect of Surface Texture on Pinhole Formation in SiO_x-Based Passivated Contacts for High-Performance Silicon Solar Cells

Journal Article Guthrey, Harvey ; Lima Salles, Caroline ; Kale, Abhijit S. ; ... - ACS Applied Materials and Interfaces

High-efficiency silicon solar cells rely on some form of passivating contact structure to reduce recombination losses at the crystalline silicon surface and losses at the metal/Si contact interface. One such structure is polycrystalline silicon (poly-Si) on oxide, where heavily doped poly-Si is deposited on a SiO_x layer grown directly on the crystalline silicon (c-Si) wafer. Depending on the thickness of the SiO_x layer, the charge carriers can cross this layer by tunneling (<2 nm SiO_x thickness) or by direct conduction through disruptions in the SiOx, often referred to as pinholes, in thicker SiO_x layers (>2 nm). In this work, wemore »« less
https://doi.org/10.1021/acsami.0c12795

Full Text Available
Pinhole Formation in Poly-Si/SiOx Passivating Contacts on Si(111)-Oriented Textures

Conference Lima Salles, Caroline ; Guthrey, Harvey ; LaSalvia, Vincenzo ; ...

Poly-Si/SiOx passivating contacts were grown on inverted pyramid and random pyramid textured wafers to investigate the hypothesis that pinhole formation is most susceptible at the valleys and edges of a textured surface. Tetramethylammonium hydroxide (TMAH) etching and electron beam induced current (EBIC) were used to assess pinhole formation and charge-carrier transport. Scanning electron microscopy revealed that TMAH etching can expose pinhole locations on textured surfaces. We show that pinholes may preferentially form at the vertices of inverted pyramids. Our TMAH and EBIC analyses on random pyramids show no preferential oxide breakup at the pyramid valleys.
https://doi.org/10.1109/PVSC45281.2020.9300568
High-Performance Passivating Contacts for Si PV Based on Engineered, Doped Nanopinholes through Dielectric Layers

Conference Lima Salles, Caroline ; Nemeth, William ; Guthrey, Harvey ; ...

We present a novel, industrially relevant method to fabricate high-performance poly-Si passivating contacts for Si PV. Passivating contacts based on SiOx/poly-Si layer stacks have been implemented in record-efficiency homojunction Si solar cells. In this technology, the carrier transport through a surface-passivating SiOx is enabled either by quantum-tunneling or nanopinholes. The doped poly-Si layer provides charge-carrier selectivity. Previously, the ISFH research group demonstrated a record 26.1% efficient Si homojunction cell, where transport pinholes in ~2 nm SiOx were produced by thermal breakdown at > 1000 degrees C, which is hard to control and is surface morphology-dependent. At room temperature, our newmore »« less
Full Text Available
Characterization of Engineered Pinholes in Dielectric Stacks of High-Performance Poly-Silicon Passivating Contacts

Conference Guthrey, Harvey ; Lima Salles, Caroline ; Nemeth, William ; ...

Passivating contact structures are expected to be implemented in > 50 % of industrially manufactured silicon photovoltaics produced over the next decade. One type of passivating contact utilizes a c-Si/dielectric/doped poly-Si layer stack. In cases where the dielectric layer/s are thick enough to impede tunneling of charge carriers, it was shown that disruptions (pinholes) in the dielectric are required to facilitate transport.[1] Pinholes in SiOx layers have typically been formed via high temperature annealing that allows localized breakup of this layer. This approach has drawbacks; 1) high temperature annealing increases cost and 2) pinhole formation is sensitive to both themore »« less
Full Text Available

Similar Records

Title: Modifications of Textured Silicon Surface Morphology and Its Effect on Poly-Si/SiO x Contact Passivation for Silicon Solar Cells

Abstract

Citation Formats

Title: Modifications of Textured Silicon Surface Morphology and Its Effect on Poly-Si/SiO _x Contact Passivation for Silicon Solar Cells