Characterization of radiation damage in multi-junction solar cells using light-biased current measurement

We present in this paper a technique that we call light-biased current measurement (LBCM) that is used to measure the current output of a component cell in a multijunction solar cell structure. The current of the solar cell is measured while it is illuminated under a simulated air mass zero (AM0) spectrum and secondary lamps are applied to boost the current in the component cells not being measured. Hence, the component cell being measured limits the current generation of the multi-junction device. This technique offers improved reliability and significant time savings compared to quantum efficiency (QE) measurement. Furthermore, this study shows that QE is almost impossible to reliably measure in low quality devices such as those severely degraded by radiation. LBCM data are compared with QE data and uncertainties of both methods are analyzed.