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Title: An Illumination- and Temperature-Dependent Analytical Model for Copper Indium Gallium Diselenide (CIGS) Solar Cells

Abstract

In this study, we present a physics-based analytical model for copper indium gallium diselenide (CIGS) solar cells that describes the illumination- and temperature-dependent current-voltage (I-V) characteristics and accounts for the statistical shunt variation of each cell. The model is derived by solving the drift-diffusion transport equation so that its parameters are physical and, therefore, can be obtained from independent characterization experiments. The model is validated against CIGS I-V characteristics as a function of temperature and illumination intensity. This physics-based model can be integrated into a large-scale simulation framework to optimize the performance of solar modules, as well as predict the long-term output yields of photovoltaic farms under different environmental conditions.

Authors:
 [1];  [2];  [2];  [2];  [1]
  1. Purdue Univ., West Lafayette, IN (United States)
  2. National Renewable Energy Lab. (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:
1376668
Report Number(s):
NREL/JA-5J00-66398
Journal ID: ISSN 2156-3381
Grant/Contract Number:
AC36-08GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
IEEE Journal of Photovoltaics
Additional Journal Information:
Journal Volume: 6; Journal Issue: 5; Journal ID: ISSN 2156-3381
Publisher:
IEEE
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; analytical model; compact model; copper indium gallium diselenide (CIGS); heterojunction; illumination dependent; temperature dependent

Citation Formats

Sun, Xingshu, Silverman, Timothy, Garris, Rebekah, Deline, Chris, and Alam, Muhammad Ashraful. An Illumination- and Temperature-Dependent Analytical Model for Copper Indium Gallium Diselenide (CIGS) Solar Cells. United States: N. p., 2016. Web. doi:10.1109/JPHOTOV.2016.2583790.
Sun, Xingshu, Silverman, Timothy, Garris, Rebekah, Deline, Chris, & Alam, Muhammad Ashraful. An Illumination- and Temperature-Dependent Analytical Model for Copper Indium Gallium Diselenide (CIGS) Solar Cells. United States. doi:10.1109/JPHOTOV.2016.2583790.
Sun, Xingshu, Silverman, Timothy, Garris, Rebekah, Deline, Chris, and Alam, Muhammad Ashraful. Mon . "An Illumination- and Temperature-Dependent Analytical Model for Copper Indium Gallium Diselenide (CIGS) Solar Cells". United States. doi:10.1109/JPHOTOV.2016.2583790. https://www.osti.gov/servlets/purl/1376668.
@article{osti_1376668,
title = {An Illumination- and Temperature-Dependent Analytical Model for Copper Indium Gallium Diselenide (CIGS) Solar Cells},
author = {Sun, Xingshu and Silverman, Timothy and Garris, Rebekah and Deline, Chris and Alam, Muhammad Ashraful},
abstractNote = {In this study, we present a physics-based analytical model for copper indium gallium diselenide (CIGS) solar cells that describes the illumination- and temperature-dependent current-voltage (I-V) characteristics and accounts for the statistical shunt variation of each cell. The model is derived by solving the drift-diffusion transport equation so that its parameters are physical and, therefore, can be obtained from independent characterization experiments. The model is validated against CIGS I-V characteristics as a function of temperature and illumination intensity. This physics-based model can be integrated into a large-scale simulation framework to optimize the performance of solar modules, as well as predict the long-term output yields of photovoltaic farms under different environmental conditions.},
doi = {10.1109/JPHOTOV.2016.2583790},
journal = {IEEE Journal of Photovoltaics},
number = 5,
volume = 6,
place = {United States},
year = {Mon Jul 18 00:00:00 EDT 2016},
month = {Mon Jul 18 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
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  • The surface and near surface structure of copper-indium-gallium-selenide (CIGS) absorber layers is integral to the producing a high-quality photovoltaic junction. By using X-ray absorption spectroscopy (XAS) and monitoring multiple elemental absorption edges with both theory and experiment, we are able to identify several features of the surface of CIGS as a function of composition and surface treatments. The XAS data shows trends in the near surface region of oxygen, copper, indium and gallium species as the copper content is varied in the films. The oxygen surface species are also monitored through a series of experiments that systematically investigates the effectsmore » of water and various solutions of: ammonium hydroxide, cadmium sulfate, and thiourea. These being components of cadmium sulfide chemical bath deposition (CBD). Characteristics of the CBD are correlated with a restorative effect that produces as normalized, uniform surface chemistry as measured by XAS. This surface chemistry is found in CIGS solar cells with excellent power conversion efficiency (<19%). The results provide new insight for CIGS processing strategies that seek to replace CBD and/or cadmium sulfide.« less
  • The surface and near surface structure of copper-indium-gallium-selenide (CIGS) absorber layers is integral to the producing a high-quality photovoltaic junction. By using X-ray absorption spectroscopy (XAS) and monitoring multiple elemental absorption edges with both theory and experiment, we are able to identify several features of the surface of CIGS as a function of composition and surface treatments. The XAS data shows trends in the near surface region of oxygen, copper, indium and gallium species as the copper content is varied in the films. The oxygen surface species are also monitored through a series of experiments that systematically investigates the effectsmore » of water and various solutions of: ammonium hydroxide, cadmium sulfate, and thiourea. These being components of cadmium sulfide chemical bath deposition (CBD). Characteristics of the CBD are correlated with a restorative effect that produces as normalized, uniform surface chemistry as measured by XAS. This surface chemistry is found in CIGS solar cells with excellent power conversion efficiency (<19%). The results provide new insight for CIGS processing strategies that seek to replace CBD and/or cadmium sulfide.« less
  • The influence of Cu(In,Ga)Se{sub 2} (CIGSe) surface roughness on the photovoltaic parameters of state of the art devices is reported, highlighting the importance of the roughness of the as-grown CIGSe absorbers on solar cell efficiencies. As-grown CIGSe surface is progressively smoothed using a chemical etch, and characterized by SEM, AFM, XPS, {mu}-Raman spectroscopy, x-ray diffraction (XRD), and reflectivity. The decrease of roughness has no marked influence on crystal structure and surface composition of the absorber. The main effect is that the total reflectivity of the CIGSe surface increases with decreasing roughness. The samples are processed into solar cells and characterizedmore » by current-voltage measurements. While the open circuit voltage (V{sub oc}) and fill factor remain constant, the short circuit current (J{sub sc}) decreases markedly with decreasing roughness, resulting in a reduction of the solar cell efficiency from 14% down to 11%, which exceeds the expected decrease from increased reflectivity. Quantum efficiency and reflectivity measurements on complete cells are performed to analyze those effects. The influence of surface roughness on the theorical effective space charge region and diffusion length is based on a simple theoretical model. This paper discusses the comparison of CIGSe solar cells with n-i-p structures.« less
  • Textured transparent conductors are widely used in thin-film silicon solar cells. They lower the reflectivity at interfaces between different layers in the cell and/or cause an increase in the path length of photons in the Si absorber layer, which both result in an increase in the number of absorbed photons and, consequently, an increase in short-circuit current density (J{sub sc}) and cell efficiency. Through optical simulations, we recently obtained strong indications that texturing of the transparent conductor in copper indium gallium (di-)selenide (CIGS) solar cells is also optically advantageous. Here, we experimentally demonstrate that the J{sub sc} and efficiency ofmore » CIGS solar cells with an absorber layer thickness (d{sub CIGS}) of 0.85 μm, 1.00 μm and 2.00 μm increase through application of a moth-eye textured resist with a refractive index that is sufficiently similar to AZO (n{sub resist} = 1.792 vs. n{sub AZO} = 1.913 at 633 nm) to avoid large optical losses at the resist-AZO interface. On average, J{sub sc} increases by 7.2%, which matches the average reduction in reflection of 7.0%. The average relative increase in efficiency is slightly lower (6.0%). No trend towards a larger relative increase in J{sub sc} with decreasing d{sub CIGS} was observed. Ergo, the increase in J{sub sc} can be fully explained by the reduction in reflection, and we did not observe any increase in J{sub sc} based on an increased photon path length.« less