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Search Publications by: Behrang Hamadani (Fed)

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Displaying 51 - 75 of 127

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