Comparative Evaluation of Rear Local Contact Patterns for P-Type Mono Crystalline Silicon PERC Solar Cell

The passivated emitter and rear cell (PERC) is an advantageous type of solar cell to reduce rear surface recombination [1] along with its improved back surface reflectivity [2]. Therefore, many research and developments have been taking place on this type of solar cell to increase the overall solar cell performance. In this study, different type of rear local contact opening patterns (line and dash) formed by industrial-type picosecond laser which has 532 nm wavelength with fixed laser contact opening (LCO) width on M2 p-type mono commercial blue wafers. Manufactured cells are investigated in terms of photovoltaic parameters depending on the rear metal fractions. We ablate rear dielectric passivation layer with 4 different LCO patterns by varying rear local contact pitches from 900 μm to 1200 μm by an increment of 100 μm using (1:1) dash pattern. Line pattern is used as reference pattern, which has 1500 μm line pitch and same contact width. Laser opening areas are analyzed by photoluminescence (PL) images as well as implied open circuit voltage (iVoc) measurements. Local contacts and formation of back surface field (BSF) has been analyzed by using scanning electron microscopy (SEM) for all types of LCOs after screen printing of aluminum paste. As a result, rear contact pattern with 3.19% metal fraction (1000 μm pitch) is found to be relatively more efficient than the others investigated in this study. When compared to reference line pattern, the optimized LCO pattern provides a gain in conversion efficiency of 0.35%, Voc of 6 mV and FF of 0.35 % on average.