Influence of Base Resistivity on Solar Cell Parameters of Double-Side Contacted Rear Junction Solar Cells

We study the dependence of solar cell parameters on base resistivity for double-side contacted n-type rear junction solar cells with boron emitter and local rear contacts. Experimental data for solar cells processed on n-type Cz Si wafers with base resistivities ranging from 2 Ω·cm to 16 Ω cm are compared to device simulations for the respective resistivity range. Our experimental data show the typical strong increase of efficiency with base resistivity in the range of 2 - 5 Ω cm and at about 10 Ω cm a saturation of efficiency with base resistivity sets in [1-4].Comparison of experimental and simulation results reveal that our experimental findings are closely reproduced assuming a constant bulk lifetime after solar cell processing. Furthermore the results of this study were implemented in an optimized solar cell process. With 14 Ω cm n-type Cz as base material solar cell efficiencies of up to 20.9% on 243.4 cm2 (total area) were achieved which was confirmed by Fraunhofer ISE CalLab.