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Title: Manufacturing and Reliability Science for CIGS Photovoltaics

Abstract

The purpose of this program was to overcome the largest challenges to investor confidence and long product lifetime in CuIn xGa 1-xSe 2 (CIGS)-based photovoltaic products: metastability, shading-induced hot spots, and potential-induced degradation. Key findings were made in each of these areas by studying CIGS reliability at the cell level, which very few groups are currently doing. Metastability was thought to be a function of the CIGS absorber. We have challenged the state-of-the-art by showing that the metastability seen in commercial products is likely to be caused by the buffer layer. SCAPS device modeling confirmed that the buffer layer has a significant influence on metastability in CIGS devices, and also led to a processing change - the introduction of CdS islands to Zn(O,S) buffer layers - that dramatically reduced metastability in CIGS solar cells. In the reverse-bias shading task, modeling showed us that 19% solar cells are possible with thin CIGS layers of 0.5 µm. We were able to fabricate 15.2% solar cells in this project, which is the highest reported efficiency of devices in the ultra-thin class. We also discovered that the best way to dissipate less power in reverse bias was to eliminate the intrinsic ZnO layer thatmore » is often used in CIGS devices. Lower power dissipation led to devices that allowed two times the maximum power point current density in reverse without damage. Potential-induced degradation (PID) is caused by the drift of Na+ ions from the back glass to the CIGS/Mo interface, followed by diffusion into the solar cells and to the CdS region. We found that PID can be slowed by using low-conductivity borosilicate glass that contains higher K and lower Na than soda-lime glass. Based on significant progress in each of the three reliability challenges, the CIGS cell-level reliability project was very successful. We have also proved that module-level degradation mechanisms can be tested and solved at the cell level.« less

Authors:
ORCiD logo [1]
  1. National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
OSTI Identifier:
1490746
Report Number(s):
NREL/TP-5K00-72953
DOE Contract Number:  
AC36-08GO28308
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 29 ENERGY PLANNING, POLICY, AND ECONOMY; photovoltaic products; metastability; Solar Cell Capacitance Simulator (SCAPS)

Citation Formats

Mansfield, Lorelle M. Manufacturing and Reliability Science for CIGS Photovoltaics. United States: N. p., 2019. Web. doi:10.2172/1490746.
Mansfield, Lorelle M. Manufacturing and Reliability Science for CIGS Photovoltaics. United States. doi:10.2172/1490746.
Mansfield, Lorelle M. Mon . "Manufacturing and Reliability Science for CIGS Photovoltaics". United States. doi:10.2172/1490746. https://www.osti.gov/servlets/purl/1490746.
@article{osti_1490746,
title = {Manufacturing and Reliability Science for CIGS Photovoltaics},
author = {Mansfield, Lorelle M},
abstractNote = {The purpose of this program was to overcome the largest challenges to investor confidence and long product lifetime in CuInxGa1-xSe2 (CIGS)-based photovoltaic products: metastability, shading-induced hot spots, and potential-induced degradation. Key findings were made in each of these areas by studying CIGS reliability at the cell level, which very few groups are currently doing. Metastability was thought to be a function of the CIGS absorber. We have challenged the state-of-the-art by showing that the metastability seen in commercial products is likely to be caused by the buffer layer. SCAPS device modeling confirmed that the buffer layer has a significant influence on metastability in CIGS devices, and also led to a processing change - the introduction of CdS islands to Zn(O,S) buffer layers - that dramatically reduced metastability in CIGS solar cells. In the reverse-bias shading task, modeling showed us that 19% solar cells are possible with thin CIGS layers of 0.5 µm. We were able to fabricate 15.2% solar cells in this project, which is the highest reported efficiency of devices in the ultra-thin class. We also discovered that the best way to dissipate less power in reverse bias was to eliminate the intrinsic ZnO layer that is often used in CIGS devices. Lower power dissipation led to devices that allowed two times the maximum power point current density in reverse without damage. Potential-induced degradation (PID) is caused by the drift of Na+ ions from the back glass to the CIGS/Mo interface, followed by diffusion into the solar cells and to the CdS region. We found that PID can be slowed by using low-conductivity borosilicate glass that contains higher K and lower Na than soda-lime glass. Based on significant progress in each of the three reliability challenges, the CIGS cell-level reliability project was very successful. We have also proved that module-level degradation mechanisms can be tested and solved at the cell level.},
doi = {10.2172/1490746},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {1}
}

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