Hideyo Iida

Analysis of silver front electrode / emitter interface structure by SPM method

The interfaces between the silver electrodes and the emitters of conventional p-type silicon solar cells have been observed by Transmission Electron Microscope (TEM), Field-Emission Scanning Electron Microscope (FE-SEM) with Energy Dispersive X-ray Spectrometer (EDS) and Scanning Probe Microscope (SPM). The observed interfaces were prepared by mechanical peeling and two steps wet-etching method. The SPM electric current image showed that the intermediate glass region between the sintered silver bulk layer and the region of the nearest neighbor to the silicon emitter surface which contained silver colloids and silver re-crystallites. The intermediate glass region limits electric current as un-uniformly dispersed current path. Density of the current path was extremely lower than the density of the silver colloids and silver re-crystallites at the nearest neighbor to the emitter surface. The observation by SPM also told us that the optimization of the intermediate glass region was another important factor for the determination of the contact resistance as well as the structure contains silver colloids and silver re-crystallites at the nearest neighbor to the emitter.