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Search Publications by: Behrang Hamadani (Fed)

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Displaying 1 - 25 of 69

Ozone generation and chemistry from 222 nm germicidal ultraviolet light in a fragrant restroom

May 20, 2024
Author(s)
Michael F. Link, Rileigh Robertson, Andrew Shore, Behrang Hamadani, Christina Cecelski, Dustin Poppendieck
Devices using 222 nm germicidal ultraviolet light (GUV222) have been marketed to reduce virus transmission indoors with low risk of occupant harm from direct UV exposure. GUV222 generates ozone, an indoor air pollutant and oxidant, under constrained

Electrical and Electroluminescence Evaluation of 17 Year Old Monocrystalline Silicon Building Integrated Photovoltaic Modules

December 25, 2023
Author(s)
Andrew Shore, Tali Schlenoff, Bakary Coulibaly, David Navon, Stephanie Moffitt, Brian P. Dougherty, Behrang Hamadani
Longterm reliable operation of photovoltaic modules is necessary to ensure the technology is key to reducing the cost of solar energy. However, degradation mechanisms in the field are not always consistent or predictable. We present a dataset of 72

Intra-grain local luminescence properties of CdSe0.1Te0.9 Thin Films

December 25, 2023
Author(s)
Ganga Neupane, Behrang Hamadani, David Albin, Joel Duenow, Matthew Reese, Susanna Thon
We report on the local photoluminescence properties of grains and grain boundaries of CdSe0.1Te0.9 thin film deposited by the colossal grain growth method using a wide-field hyperspectral imaging technique. We observed significant variations in the

Imaging local luminescence variations in CdSe0.1Te0.9 thin films grown by the colossal grain growth process.

August 4, 2023
Author(s)
Ganga Neupane, Andrew Winchester, Nicolas Marquez Peraca, David Albin, Joel Duenow, Matthew Reese, Sujitra Pookpanratana, Susanna Thon, Behrang Hamadani
Clear visualization and understanding of luminescence properties of grain interiors and grain boundaries in polycrystalline thin-film photovoltaic materials are crucial to achieving high-performance solar cells. Luminescence-based measurements, for example

Ozone Generation from a Germicidal Ultraviolet Lamp with Peak Emission at 222 nm

July 21, 2023
Author(s)
Michael F. Link, Andrew Shore, Behrang Hamadani, Dustin Poppendieck
Recent interest in commercial devices containing germicidal ultraviolet lamps with a peak emission wavelength at 222 nm (GUV222) has focused on mitigating virus transmission indoors while posing minimum risk to human tissue. However, 222 nm light can

What limits the voltage of GaAs photovoltaic devices under low indoor light?

June 19, 2023
Author(s)
Behrang Hamadani, Margaret Stevens, Matthew Lumb, Kenneth Schmieder
The external radiative efficiency of a photovoltaic device is a useful metric to compare different photovoltaic technologies and material systems. However, under low-intensity indoor lighting, a particular open-circuit voltage dependence arises that cannot

Hyperspectral Imaging of Localized, Optically-Active Defects in GaAs Solar Cells

November 14, 2022
Author(s)
Behrang Hamadani, Margaret Stevens, Brianna Conrad, Matthew Lumb, Eric Armour, Kenneth Schmieder
A novel hyperspectral imaging instrument with dual electroluminescence and photoluminescence capability was used to image and analyze localized radiative defects in rear-junction GaAs solar cells grown at 1 µm/min. The absolute photon emission rates were

Visualizing Localized, Radiative Defects in GaAs Solar Cells

September 1, 2022
Author(s)
Behrang Hamadani, Margaret Stevens, Brianna Conrad, Matthew Lumb, Kenneth Schmieder
We have used a calibrated, wide-field hyperspectral imaging instrument to obtain absolute spectrally and spatially resolved photoluminescence images in high growth-rate, rear-junction GaAs solar cells from 300 K to 77 K. At the site of some localized

Color-Temperature Dependence of Indoor Organic Photovoltaic Performance

March 5, 2022
Author(s)
Boya Zhang, Justin Bonner, Lakshmi Murthy, Thien Nguyen, Fong-Yi Cao, Yen-Ju Cheng, Behrang Hamadani, Julia Hsu
Organic materials are uniquely suited for indoor light energy harvesting because they absorb mostly in the visible spectrum and the absence of ultraviolet light minimizes their degradation. However, the performance of photovoltaic devices under indoor

Heterosubstrate Illumination Effects in III-V Solar Cells

February 16, 2022
Author(s)
Brianna Conrad, Behrang Hamadani
Reference cell-based current versus voltage ( I–V ) measurements assume that the effect of an illumination spectrum on a solar cell's performance can be fully captured by the multiplication of the spectrum with the device's spectral response and subsequent

Investigating Sub-bandgap Spectral Effects in GaInP-on-Ge Solar Cells

August 26, 2021
Author(s)
Brianna Conrad, Behrang Hamadani
There is a fundamental understanding in photovoltaics that sub-bandgap light will not be absorbed in the solar cell and therefore will not affect the power generation. We have shown a novel phenomenon in which sub-bandgap illumination is required for good

Solar Cell Performance Measurements Under Artificial Lighting Sources

January 5, 2021
Author(s)
Behrang Hamadani
In recent years, there has been a growing interest in measurements of photovoltaic solar cells under ambient artificial lighting such as light emitting diode (LED) or fluorescent light sources. Certain classes of solar cells are considered very good

Understanding Photovoltaic Energy Losses under Indoor Lighting Conditions

July 28, 2020
Author(s)
Behrang H. Hamadani
The external luminescence quantum yield as a function of the solar cell current density when exposed to low indoor light was estimated based on absolute electroluminescence measurements and a self-consistent use of the electro-optical reciprocity

3D printed optical concentrators for LED arrays

July 19, 2020
Author(s)
Behrang H. Hamadani, Jonathan E. Seppala, Clarence J. Zarobila
Additive manufacturing methods based on photopolymerization offer a great potential for fabrication of high quality, highly transparent optical components. One appropriate use of these technologies is related to fabrication of parts that can be used in