Short-circuit current density mapping for solar cells

Abstract

A map of local short-circuit current density (JSC) of a solar cell at standard irradiance spectra is a desirable source of information for current-loss analysis and device optimization. In this work, we present a new and easily implementable method to obtain such JSC maps as well as local external quantum efficiency graphs with a spatial resolution of about 100µm, exemplified for silicon solar cells. The method is based on a pixel by pixel interpolation of external quantum efficiency maps obtained by spectrally resolved light-beam induced current measurements (SR-LBIC). The local data is integrated with an AM1.5G spectrum to obtain a JSC map with no additional measurement time beyond SR-LBIC image acquisition. The averaged currents over a map are in good agreement with global current–voltage measurements. Some of the possible applications of this method are presented and exemplified, including local quantum efficiency of a cast-mono solar cell, separation of JSC contributions from front side and bulk, quantitative determination of the electrical shading effect in IBC cells, the impact of the irradiance spectrum on local JSC for indoor photovoltaic applications and also the separation of optical and electrical current losses with newly introduced Pseudo-JSC maps based on internal quantum efficiency maps. Finally, the resulting JSC maps also present valuable information for several existing local cell-parameter imaging methods. This basic approach leads to an easily accessible, spatially resolved short-circuit current loss-analysis, which is in principle applicable to any solar cell structure.