A contactless method of emitter sheet resistance measurement for silicon wafers

Abstract

The emitter sheet resistance is an essential parameter impacting the efficiency of silicon solar cells with diffused layers. Conventional measurement methods of this parameter either require electrical contacts or are impacted by the bulk resistivity of the measured samples. In this study, a novel method based on the combination of eddy-current conductance and photoluminescence imaging is developed for a contactless determination of the emitter sheet resistance. Numerical simulation is used to establish the correlation between the photoluminescence profile and the sum of the emitter and bulk resistance. Together with eddy-current conductance measurements, the emitter sheet resistance and bulk resistance can be separated. The accuracy of the method is validated experimentally, and its uncertainty is investigated. The contactless nature of the developed method makes it attractive for inline inspection of diffused layers in solar cell manufacturing.