Triple-junction amorphous silicon solar cells have been characterized using two techniques to identify the current-limiting component cell after a variety of radiation exposure experiments. The first technique is calculation of integrated current from quantum efficiency (QE) data, which is commonly accepted by the photovoltaics community for predicting the current output of a solar cell. This study shows that significant sources of uncertainty make quantum efficiency measurements unreliable in low quality multi-junction devices such as those that have been severely degraded by particle radiation.
An alternate method is examined whereby a solar cell is illuminated by simulated air-mass zero (AM0) light and secondary filtered lamps are used to boost the current in two of the three component cells. Thorough characterization of the test condition shows that the targeted component cell limits the current of the device as a result of the boost light, making the current measured from the device under test represent the current output of the desired component cell. This method is henceforth called light-biased current measurement (LBCM). An additional benefit of the light-biased current measurement is the significantly reduced time required to make a measurement compared to quantum efficiency measurements.
Successful repeatability and reproducibility experiments further validate this test method. As shown during reproducibility testing, one of the two solar simulators used introduces an expected increase in the measurement uncertainty due its unstable intensity output. The increase in variance of the data is well correlated to the estimated measurement uncertainty.