The Effect of Nonuniform Emitter Sheet Resistance on PERC Solar Cell Performance

Abstract

The aim of this research work is to study the effects of non-uniform emitter sheet resistance on the performance of PERC solar cells. For this purpose, we used different simulation techniques including EDNA 2, MATLAB and Griddler 2.5 Pro. We calibrated the phosphorous doping profiles with Nmax of 4E20, 3.5E20, 3E20, 2.5E20, 2E20, 1.5E20 and 1E20 by using EDNA 2. The results show that the emitter saturation current densities are decreased for corresponding increase in sheet resistance during phosphorous diffusion. In this way we find a relationship between emitter sheet resistances and recombination current densities and developed a MATLAB function from it. By assuming maximum emitter sheet resistance and the corresponding minimum recombination current density at the centre of the cell, we determined their average values from the same MATLAB function. These average values were then used as input parameters for computer simulations Griddler 2.5 Pro, to assess the effect of non-uniformities in emitter sheet resistance and recombination currents on the performance of p- PERC solar cells. The open-circuit voltage, short-circuit current density, fill factor and efficiency are calculated as a function of the difference between the maximum and minimum value of emitter sheet resistance. The results show that the open-circuit voltage and the efficiency of p-PERC solar cell are decreased if the difference between maximum and minimum value of emitter sheet resistance is increased from 0.45 ohm/sq to 19.3 ohm/sq. Whereas the fill factor is increased for the corresponding increase in the difference between maximum and minimum value of emitter sheet resistance.