Voltage calibration of luminescence images of silicon solar cells

A variety of methods extracting spatially resolved information of solar cell parameters using luminescence imaging on silicon solar cells have been introduced in the past years. Nearly, all methods base on calibrating the local luminescence intensity to local junction voltage. The different methods, however, use different approaches to calibrate the luminescence images to local junction voltage. The assumptions made by the voltage calibration approaches are fundamental for a correct voltage calibration and hence for a correct extraction of other relevant local solar cell parameters. In this work, we review the different voltage calibration approaches and analyse the validity and the effect of the underlying assumptions carefully using circuit simulation results. We present experimental results of voltage calibrated luminescence images of a multicrystalline silicon solar cell using different voltage calibration approaches. We show the relevance of accurate voltage calibration by performing a sensitivity analysis investigating the sensitivity of local cell parameter results obtained by a method known from literature with respect to changes in the calibration constant. We conclude proposing an approach for voltage calibration which is the most reasonable trade-off between accuracy and sufficiently low data acquisition times.