Development of High-efficiency Industrial p-type Multi-crystalline PERC Solar Cells with Efficiency Greater Than 21%

AbstractIn recent years, rather fine-grained multicrystalline Si material seems to have outperformed most quasi-mono material in industrial production. We have developed an industrial process for PERC cells, specifically suitable for 156×156 mm2 fine-grained multicrystalline p-type wafers, and we reached cell efficiencies of up to 21.25% with a Voc of 667.8mV, which seems to be the highest reported efficiency and Voc for industrial p-type mc silicon solar cells. In this work, we describe recent changes to our process sequence, adjust a measurement method to low saturation currents, and give a detailed loss analysis with the help of numerical device simulation. The improved surface passivation and optimized doping profile have reduced the emitter saturation current to 25.6 fA/cm2, which is the main contribution to the cell efficiency improvements. Particular attention is paid to fill factor losses due to recombination rate saturation in the base. But Voc is still dominated by recombination at the rear contacts. Accordingly, improvement strategies need be adjusted