Title: Effect of Surface Texture on Pinhole Formation in SiO_x-Based Passivated Contacts for High-Performance Silicon Solar Cells

Abstract

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, we study structures with tunneling- or pinhole-like SiO_x contacts grown on pyramidally textured c-Si wafers and expose variations in the SiOx layer properties related to surface morphology using electron-beam-induced current (EBIC) imaging. Using EBIC, we identify and mark regions with potential pinholes in the SiO_x layer. We further perform high-resolution transmission electron microscopy on the same areas, thus allowing us to directly correlate locally enhanced carrier collection with variations in the structure of the SiO_x layer. Our results show that the pinholes in the SiO_x layer preferentially form in different locations based on the annealing conditions used to form the device.more » With greater understanding of these processes and by controlling the surface texture geometry, there is potential to control the size and spatial distribution of oxide disruptions in silicon solar cells with poly-Si on oxide-type contacts; usually, this is a random phenomenon on polished or planar surfaces. Such control will enable us to consistently produce high-efficiency devices with low recombination currents and low junction resistances using this contact structure.« less

Authors:

Guthrey, Harvey  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-1574-3379"

Lima Salles, Caroline  ^[2];

• Search DOE PAGES for author "Lima Salles, Caroline"
• Search DOE PAGES for ORCID "0000-0003-1537-3611"

Kale, Abhijit S. ^[2]; Nemeth, William ^[1]; Page, Matthew ^[1]; Agarwal, Sumit ^[3]; Young, David L. ^[1]; Al-Jassim, Mowafak ^[1]; Stradins, Paul ^[1]

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+ Show Author Affiliations

1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
2. National Renewable Energy Lab. (NREL), Golden, CO (United States); Colorado School of Mines, Golden, CO (United States)
3. Colorado School of Mines, Golden, CO (United States)

Publication Date:

Tue Dec 01 00:00:00 EST 2020

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:

1755723

Report Number(s):

NREL/JA-5K00-77115
Journal ID: ISSN 1944-8244; MainId:26061;UUID:b29e7e98-4068-4bd6-80ad-3779ff0ae32a;MainAdminID:19044

Grant/Contract Number:  

AC36-08GO28308

Resource Type:

Accepted Manuscript

Journal Name:

ACS Applied Materials and Interfaces

Additional Journal Information:

Journal Volume: 12; Journal Issue: 50; Journal ID: ISSN 1944-8244

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

14 SOLAR ENERGY; EBIC; oxide passivation; pinholes; pyramid texture; silicon solar cell; passivating contact; surface texture