Challenges of irradiance-mode spectral response measurements

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 (I_sc) of solar cells under air mass 1.5 standard reference spectrum. In this work, a monochromator-based approach was combined with a light emitting diode (LED) array-operated system based on an integrating sphere design to obtain the irradiance-mode SR curves for a variety of cells, including large-area cells with dimensions up to 155 mm. Challenges associated with these measurements, including light uniformity, collimation issues and light bias effects are discussed. I_sc calculations using this approach and intercomparison with other laboratories confirm the accuracy of the outlined methodology.