INVESTIGATION OF REAR CONTACT RESISTANCE OF LINE CONTACTED INDUSTRIAL PERC SOLAR CELLS

摘要

In this work we present the results of the contact resistance investigation of high efficiency line contacted industrial Passivated Emitter and Rear solar Cells (PERC). Especially the homogeneity of the contact resistance over the rear side of a PERC structure as well as the influence of a high amount of voiding inside the local rear contacts on the contact resistance is analyzed. The rear contact resistance is measured by the Transfer Length Method (TLM) and evaluated using our recently developed evaluation method utilizing 2D Sentaurus Device simulations of the sample structure. These evaluations yield a low mean specific rear contact resistance and demonstrate that it is homogeneously distributed over the rear side of a PERC solar cell even for a high percentage of rear contact voiding above 60%. The reason for the voiding to have little effect on the contact resistance is that Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray spectroscopy (EDX) images reveal a metallization along the edges of voided rear contacts. By applying our cell processes and screen-printing pastes this edge metallization is sufficient to achieve an adequate electrical connection between the base and the rear metallization of actual high efficiency PERC solar cells.