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Restored Passivation after Complete Removal of Front Poly-Si Between the Grid in Poly-Si/SiO2 Front/Back Cells

Conference ·
DOI:https://doi.org/10.1063/5.0089756· OSTI ID:1890145
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This work explores the use of wet chemical etching to completely remove the front poly-Si layer between grid lines of a front/back poly-Si/SiO2 passivated contact device. The purpose of the work is to provide excellent passivation under the metal grid, but to also maximize Jsc by eliminating optical absorption in the front poly-Si. We show that after a high temperature anneal to distribute carriers in the poly-Si/SiO2/c-Si interface all of the poly-Si can be removed selectively with TMAH, using the SiO2 as an etch-stop layer. The etched surface can be repassivated back to its original level with the addition of a SiNx/Al2O3 stack grown on the preserved tunnelling oxide layer followed by a short forming gas anneal. Using symmetric 100 - 200 nm intrinsically doped poly-Si/SiO2 on textured n-type wafer templates we show absolute device efficiency enhancement from 15% to 21% by increasing the Jsc by 12 mA/cm2 after removing the front poly-Si and repassivating while effectively preserving the Voc, and FF of the device. IQE values are similar to PERC devices in the short wavelength range.
Research Organization:
National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
DOE Contract Number:
AC36-08GO28308
OSTI ID:
1890145
Report Number(s):
NREL/CP-5900-84146; MainId:84919; UUID:0cf5ee68-d1c4-4ad6-b482-a002c1b62c4c; MainAdminID:67642
Country of Publication:
United States
Language:
English

References (7)

Temperature-induced stoichiometric changes in thermally grown interfacial oxide in tunnel-oxide passivating contacts journal December 2020
An improved TMAH Si-etching solution without attacking exposed aluminum journal March 2001
Efficiency Roadmap for Evolutionary Upgrades of PERC Solar Cells by TOPCon: Impact of Parasitic Absorption journal March 2020
Reactive ion etched, self-aligned, selective area poly-Si/SiO2 passivated contacts journal November 2020
monoPoly™ cells: Large-area crystalline silicon solar cells with fire-through screen printed contact to doped polysilicon surfaces journal December 2018
Ultra‐Thin Poly‐Si Layers: Passivation Quality, Utilization of Charge Carriers Generated in the Poly‐Si and Application on Screen‐Printed Double‐Side Contacted Polycrystalline Si on Oxide Cells journal August 2020
The application of poly-Si/SiOx contacts as passivated top/rear contacts in Si solar cells journal January 2017

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Related Subjects

SOLAR ENERGY
etching
optical absorption
semiconductor materials