Insights into Na+ Diffusion in Silicon Modules under Operating Conditions: Measuring Low Concentrations by D-SIMS

Jacob Clenney, Erick Martinez Loran, Guillaume Von Gastrow, David Fenning, Rico Meier, Mariana I. Bertoni

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Sodium induced shunting under an electric field is a challenging reliability issue in crystalline Si solar modules. THe source of this Potential-Induced Degradation of the Shunting type (PID-s) is well understood [1] and its influence on power loss has been intensively studied based on phenomenological models on cell or module level relating the experimental power-loss to stressing parameters (time, temperature, voltage) [1]. However, little is known about the Na ion migration kinetics, responsible for PID on a microscopic level, and its quantitative relation to the efficiency degradation. In this paper we present our investigations of sodium ion migration in Ethylene-Vinyl Acetate (EVA) and silicon through Dynamic Secondary Ion Mass Spectroscopy (D-SIMS). Each sample was annealed at field relevant temperatures from 60-90 °C to address typical migration mechanisms of common PV installations. Analysis of the SIMS migration profiles revealed a diffusivity constant D0,EVA = 0.09 ± 0.14 cm2/s and an activation energy EA,EVA = 0.85 ±.04 eV for Na in EVA and diffusivities higher than extrapolated literature values in silicon (D0,Si = (3.03 ± 2.42)x10-5 cm2/s, and EA,Si = 0.98 ± 0.02 eV). The new insight will be included in a drift-diffusion based degradation model accounting for the partition coefficient across all relevant interfaces. This model can assist in predicting PID-failure in the field based on the given mudle stack and the diffusion of Na+ through each material. This tool can be used for process optimization as well as material selection significantly reducing the cost and time to validate a technology.

Original languageEnglish (US)
Title of host publication2020 47th IEEE Photovoltaic Specialists Conference, PVSC 2020
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages863-867
Number of pages5
ISBN (Electronic)9781728161150
DOIs
StatePublished - Jun 14 2020
Event47th IEEE Photovoltaic Specialists Conference, PVSC 2020 - Calgary, Canada
Duration: Jun 15 2020Aug 21 2020

Publication series

NameConference Record of the IEEE Photovoltaic Specialists Conference
Volume2020-June
ISSN (Print)0160-8371

Conference

Conference47th IEEE Photovoltaic Specialists Conference, PVSC 2020
CountryCanada
CityCalgary
Period6/15/208/21/20

Keywords

  • PID
  • SIMS
  • degradation mechanism
  • impurity migration
  • reliability
  • silicon
  • solar cell

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Industrial and Manufacturing Engineering
  • Electrical and Electronic Engineering

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