Measuring the External Quantum Efficiency of Tandem Photovoltaic Modules Using an LED-Based Solar Simulator

An external quantum efficiency (EQE) measurement procedure for full-size tandem modules using a light-emitting diode (LED)-based solar simulator is introduced. This elegant procedure uses the LED light source for both, setting a close to one-sun bias spectrum and performing the actual EQE measurement by modulating individual LED channels. Measurement comparisons using filtered silicon solar cells and a perovskite on silicon (PSC/Si) single-cell module demonstrate good agreement between the EQEs obtained with the presented procedure and reference EQEs, determined at Fraunhofer ISE CalLab PV Cells and the National Metrology Institute of Germany. Applying the procedure to a full-size PSC/Si tandem module results in a close match of the full module EQE and the EQE of an optically similar single-cell module measured at CalLab PV Cells. Performing a spectral adjustment of the LED solar simulator based on the full-module and single-cell module EQE, only minor spectral variations, reflected in minimal deviations of the resulting spectral mismatch factors of less than 0.4%, are determined. The presented results confirm the applicability of the procedure as an efficient and accurate approach for EQE measurements and underline its overall relevance for the calibration of full-size tandem modules.