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Search Publications by: John Roller (Assoc)

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Displaying 1 - 14 of 14

Reconciling LED and Monochromator-based Measurements of Spectral Responsivity

August 1, 2019
Author(s)
John F. Roller, Behrang H. Hamadani
The irradiance spectral responsivity is an important measurement characteristic for a reference solar cell and has served as a primary reference cell calibration method for a growing number of national labs in recent years. This paper discusses the process

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

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

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

SRM 1450d, Fibrous-Glass Board, for Thermal Conductivity from 280 K to 340 K

August 1, 2011
Author(s)
Robert R. Zarr, Amanda C. Harris, John F. Roller, Stefan D. Leigh
Thermal conductivity measurements at and near room temperature are presented as the basis for certified values of thermal conductivity for SRM 1450d, Fibrous Glass Board. The measurements have been conducted in accordance with a randomized full factorial