Elimination of Artifacts in External Quantum Efficiency Measurements of Multijunction Solar Cells Using a Pulsed Voltage Bias

A pulsed voltage bias (PVB) method is demonstrated to eliminate artifacts in external quantum efficiency (EQE) measurements of multijunction solar cells that are caused by the shunt effect or the combined effects of shunt and luminescence coupling. This method uses a PVB superimposed on the dc voltage and light biases in conventional EQE measurements. The PVB method is compared with the recently reported pulsed light bias (PLB) method and unity rule. It is found that the PVB method has a similar accuracy as the PLB method, while the unity rule shows a larger discrepancy between the measurement results and the true EQE under certain conditions. Experimental results show that, with either the PVB or PLB method, one only needs to measure the EQE at one wavelength point and scale accordingly at the other wavelengths to obtain the entire spectrum in the wavelength range of the subcell under test, making both methods convenient to use in practice.