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Search Publications by: Behrang Hamadani (Fed)

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Displaying 26 - 50 of 67

Modulated Photocurrent Measurements in Double Junction Solar Cells

November 4, 2018
Author(s)
Nicolas Marquez Peraca, Behrang Hamadani
Frequency dependent external quantum efficiency (EQE) measurements were performed on double junction solar cells by a custom-designed system consisting of an array of various monochromatic LEDs. Some LEDs were pulsed as a function of frequency while others

Frequency response of the external quantum efficiency in multijunction solar cells

June 29, 2017
Author(s)
Nicolas Marquez Peraca, D T. Bilir, Behrang Hamadani
The frequency dependence of the external quantum efficiency (EQE) of high-quality multijunction solar cells was examined by the modulated photocurrent spectroscopy method via an optical setup comprised of a light-pipe-coupled compact LED array. The optical

Spectral dependence of carrier lifetimes in silicon for photovoltaic applications

December 21, 2016
Author(s)
John F. Roller, Yu-Tai Li, Mario Dagenais, Behrang H. Hamadani
Charge carrier lifetimes in photovoltaic-grade silicon wafers were measured by a spectral-dependent, quasi-steady-state photoconductance technique. Narrow bandwidth LEDs were used to excite excess charge carriers within the material, and the effective

Challenges of Irradiance-mode Spectral Response Measurements

October 16, 2014
Author(s)
Behrang H. Hamadani, John F. Roller, Brian P. Dougherty, Howard W. Yoon
Irradiance-mode spectral response measurements of solar cells are important because they provide a direct, reliable and accurate route for determination of the short circuit current (Isc) of solar cells under air mass 1.5 standard reference spectrum. In

Large-area irradiance-mode spectral response measurements of solar cells by a light-emitting-diode- based integrating sphere source

May 30, 2014
Author(s)
Behrang H. Hamadani, John F. Roller, Andrew M. Shore, Brian P. Dougherty, Howard W. Yoon
An irradiance-mode absolute differential spectral response measurement system based on a light emitting diode (LED) array is described. The LEDs are coupled to an integrating sphere whose output irradiance is uniform to better than 2 % over an area of 160

Fast and Reliable Spectral Response Measurements of PV Cells Using Light Emitting Diodes

January 1, 2014
Author(s)
Behrang H. Hamadani, John F. Roller, Brian P. Dougherty, Howard W. Yoon
We present a measurement system for absolute differential spectral responsivity of solar cells based on high-powered LED arrays coupled to an optical light guide capable of large area illumination. Two different measurement techniques were developed and

Local electrical characterizations of cadmium telluride solar cells using low energy electron beam

October 1, 2013
Author(s)
Heayoung Yoon, Paul M. Haney, Dmitry A. Ruzmetov, Hua Xu, Marina S. Leite, Behrang H. Hamadani, Albert A. Talin
We investigate local electronic properties of cadmium telluride solar cells using electron beam induced current (EBIC) measurements with current-collecting patterned contacts. EBIC measurements are performed with a spatial resolution as high as ≈20 nm both

Absolute spectral responsivity measurements of solar cells by a hybrid optical technique

July 15, 2013
Author(s)
Behrang H. Hamadani, John F. Roller, Brian P. Dougherty, Fiona Persaud, Howard W. Yoon
An irradiance mode, absolute differential spectral response measurement system for solar cells is presented. The system is based on combining the monochromator-based approach of determining the power mode spectral responsivity of cells with an LED-based

Modulated photocurrent spectroscopy of CdTe/CdS solar cells-equivalent circuit analysis

May 20, 2013
Author(s)
Behrang H. Hamadani, John F. Roller, Kounavis Panagiotis, Nikolai B. Zhitenev, David J. Gundlach
We have used the technique of photocurrent modulated spectroscopy to investigate the dynamic response of charge carrier transport in thin film CdTe/CdS solar cells as a function of light bias and temperature over a broad excitation frequency range. The

High-Resolution Local Current Measurement of CdTe Solar Cells

October 4, 2012
Author(s)
Heayoung Yoon, Dmitry A. Ruzmetov, Paul M. Haney, Marina S. Leite, Behrang H. Hamadani, Albert A. Talin, Nikolai B. Zhitenev
We investigate local electronic properties of CdTe solar cells using electron beam to excite electron-hole pairs and evaluate spatially resolved photocurrent characteristics. Standard semiconductor processes were used to fabricate Ohmic metal contacts on

Towards realization of a large-area, LED-based solar simulator

November 27, 2011
Author(s)
Behrang H. Hamadani, Kangbin Chua, John F. Roller, Howard W. Yoon, Brian P. Dougherty
LED-based solar simulators have shown great promise as alternative light sources for indoor testing of PV cells as compared to their traditional counterparts. However, large-area uniform illumination more suitable for larger cells and module measurements

Imaging of nanoscale charge transport in bulk heterojunction solar cells

June 17, 2011
Author(s)
Behrang H. Hamadani, Nadine E. Gergel-Hackett, Paul M. Haney, Nikolai B. Zhitenev
We have studied the local charge transport properties of organic bulk heterojunction solar cells based on the blends of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) with a photoconductive atomic force microscope (PCAFM). We

Three-Dimensionally Structured CdS/CdTe Photovoltaics on Dual Interdigitated Back-Contacts

April 8, 2011
Author(s)
Carlos M. Hangarter, Behrang Hamadani, Ryan F. Need, Carlos R. Beauchamp, Hua Xu, John E. Bonevich, Nikolai Zhitenev, Daniel Josell
The fabrication and properties of three-dimensionally structured CdS/CdTe solar cells with back-contacts are described. Fabrication entails electrodeposition of CdS at submicrometer length scales on one of two metal electrodes interdigitated in a comb

Flexible Titanium Dioxide Memory

April 25, 2010
Author(s)
Nadine Gergel-Hackett, Laurie Stephey, Barbara Dunlap, Behrang Hamadani, David J. Gundlach, Curt A. Richter

Origin of Nanoscale Variations in Photoresponse of an Organic Solar Cell

April 22, 2010
Author(s)
Behrang H. Hamadani, Suyong S. Jung, Paul M. Haney, Lee J. Richter, Nikolai B. Zhitenev
Photo generated charge transport in bulk heterojunction (BHJ) solar cells is strongly dependent on the active layer nanomorphology resulting from phase segregation and connectivity of the donor and acceptor regions. Scanning probe-based techniques and in

Three-Dimensionally Structured Thin Film Heterojunction Photovoltaics on Interdigitated Back-Contacts

February 1, 2010
Author(s)
Daniel Josell, Carlos R. Beauchamp, Behrang H. Hamadani, Suyong S. Jung, Jonathan E. Guyer, Abhishek Motayed, Carlos M. Hangarter, Nadine E. Gergel-Hackett, Hua Xu, Nikolai B. Zhitenev
Fabrication and properties of three-dimensionally structured back-contact heterojunction solar cells are described. A variety of devices are explored, all of which were fabricated by electrochemical deposition of a semiconducting material on one of two