Reconciling LED and monochromator-based measurements of spectral responsivity in solar cells

Irradiance spectral responsivity is an important measurement characteristic for a solar cell and has served as a primary reference cell calibration parameter for a growing number of national laboratories in recent years. This paper discusses the process by which a packaged reference cell is calibrated using the power spectral responsivity from a monochromator-based measurement coupled with discrete irradiance responsivity measurements from a light-emitting diode (LED) array source to uniformly illuminate the cell. To accurately transfer the responsivity from a calibrated detector cell to a fully packaged reference cell, differences in the measurements of power and irradiance responsivities due to the two separate lighting sources must be reconciled. The spectral effects of using LEDs, as well as other physical packaging effects, are discussed in detail, and a comprehensive treatment of the uncertainty components from both approaches is presented.