skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

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

Journal Article · · 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 SiOx layer grown directly on the crystalline silicon (c-Si) wafer. Depending on the thickness of the SiOx layer, the charge carriers can cross this layer by tunneling (<2 nm SiOx thickness) or by direct conduction through disruptions in the SiOx, often referred to as pinholes, in thicker SiOx layers (>2 nm). In this work, we study structures with tunneling- or pinhole-like SiOx 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 SiOx 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 SiOx layer. Our results show that the pinholes in the SiOx layer preferentially form in different locations based on the annealing conditions used to form the device. 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.

Research Organization:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
Grant/Contract Number:
AC36-08GO28308
OSTI ID:
1755723
Report Number(s):
NREL/JA-5K00-77115; MainId:26061; UUID:b29e7e98-4068-4bd6-80ad-3779ff0ae32a; MainAdminID:19044
Journal Information:
ACS Applied Materials and Interfaces, Vol. 12, Issue 50; ISSN 1944-8244
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

References (34)

A 720 mV open circuit voltage SiO x : c ‐Si:SiO x double heterostructure solar cell journal December 1985
A review of focused ion beam milling techniques for TEM specimen preparation journal June 1999
Interdigitated back contact solar cells with polycrystalline silicon on oxide passivating contacts for both polarities journal July 2017
Silicon heterojunction solar cell with interdigitated back contacts for a photoconversion efficiency over 26% journal March 2017
Understanding the limits of ultrathin SiO2 and SiON gate dielectrics for sub-50 nm CMOS journal September 1999
An investigation of the thermal stability of the interfacial oxide in polycrystalline silicon emitter bipolar transistors by comparing device results with high‐resolution electron microscopy observations journal January 1987
Extraction of Surface Recombination Velocity at Highly Doped Silicon Surfaces Using Electron-Beam-Induced Current journal January 2015
Working principle of carrier selective poly-Si/c-Si junctions: Is tunnelling the whole story? journal December 2016
Three-Dimensional Electron Energy Deposition Modeling of Cathodoluminescence Emission near Threading Dislocations in GaN and Electron-Beam Lithography Exposure Parameters for a PMMA Resist journal November 2012
Temperature-dependent contact resistance of carrier selective Poly-Si on oxide junctions journal October 2018
IBC c-Si solar cells based on ion-implanted poly-silicon passivating contacts journal December 2016
SiO2 surface passivation layers – a key technology for silicon solar cells journal October 2018
n-Type Si solar cells with passivating electron contact: Identifying sources for efficiency limitations by wafer thickness and resistivity variation journal December 2017
A simple method for pinhole detection in carrier selective POLO-junctions for high efficiency silicon solar cells journal December 2017
Pinhole density and contact resistivity of carrier selective junctions with polycrystalline silicon on oxide journal June 2017
Depletion region surface effects in electron beam induced current measurements journal September 2016
Three-dimensional electron microscopy simulation with the CASINO Monte Carlo software journal May 2011
A Simple Model Describing the Symmetric <formula formulatype="inline"><tex Notation="TeX">$I\hbox{--}V$</tex></formula> Characteristics of <formula formulatype="inline"><tex Notation="TeX">$\hbox{p}$</tex></formula> Polycrystalline Si/ <formula formulatype="inline"><tex Notation="TeX">$\hbox{n}$</tex></formula> Monocrystalline Si, and <formula formulatype="inline"> <tex Notation="TeX">$\hbox{n}$</tex></formula> Polycrystalline Si/<formula formulatype="inline"><tex Notation="TeX">$\hbox{p}$</tex></formula> Monocrystalline Si Junctions journal May 2014
Early stage evolution kinetics of the polysilicon/single‐crystal silicon interfacial oxide upon annealing journal January 1991
Recombination behavior and contact resistance of n+ and p+ poly-crystalline Si/mono-crystalline Si junctions journal December 2014
Oxidation induced stresses and some effects on the behavior of oxide films journal November 1983
Stress effect on the kinetics of silicon thermal oxidation journal March 2001
Metallization-induced recombination losses of bifacial silicon solar cells: Metallization-induced recombination losses of bifacial silicon solar cells
  • Edler, Alexander; Mihailetchi, Valentin D.; Koduvelikulathu, Lejo J.
  • Progress in Photovoltaics: Research and Applications, Vol. 23, Issue 5 https://doi.org/10.1002/pip.2479
journal February 2014
Laser contact openings for local poly-Si-metal contacts enabling 26.1%-efficient POLO-IBC solar cells journal November 2018
Understanding the charge transport mechanisms through ultrathin SiO x layers in passivated contacts for high-efficiency silicon solar cells journal February 2019
Effect of Crystallographic Orientation and Nanoscale Surface Morphology on Poly-Si/SiO x Contacts for Silicon Solar Cells journal October 2019
Structure and morphology of polycrystalline silicon‐single crystal silicon interfaces journal April 1985
Introducing pinhole magnification by selective etching: application to poly-Si on ultra-thin silicon oxide films journal September 2017
Stress‐related problems in silicon technology journal September 1991
Study of Pinhole Conductivity at Passivated Carrier-selected Contacts of Silicon Solar Cells journal August 2016
Polysilicon emitters for silicon concentrator solar cells conference January 1990
Tunneling or Pinholes: Understanding the Transport Mechanisms in SiOx Based Passivated Contacts for High-Efficiency Silicon Solar Cells
  • Kale, Abhijit S.; Nemeth, William; Nanayakkara, Sanjini U.
  • 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) https://doi.org/10.1109/PVSC.2018.8547211
conference June 2018
Nonuniform Charge Collection in SiO x -Based Passivated-Contact Silicon Solar Cells conference June 2019
Dopant diffusion from p + -poly-Si into c-Si during thermal annealing conference June 2016