Correcting the Effect of LED Spectra on External Quantum Efficiency Measurements of Solar Cells

Light emitting diodes (LEDs) are increasingly being used as light sources in studying solar cells due to their high power, low cost, and long bulb lifetimes. However, LEDs do not provide the monochromatic illumination that is desired for an external quantum efficiency measurement. This study investigates the error associated with using a broad emission spectrum instead of monochromatic light on measurements of the external quantum efficiency of silicon solar cells. An analytical approach is used to quantify the impact of the finite spectral width of LEDs. The approach is then extended to provide a method that corrects for the resulting error in the measured external quantum efficiency (EQE). It is shown that after applying the correction method to the measured EQE, the absolute error can be reduced from 1%–2% to under 0.5%.