Development of Bifacial P-Pert and N-Pert Solar Cells With Reduced Thermal Processing and Comparison of Bifacial Coefficients
Abstract
Bifacial n-type TOPCon and p-type PERC solar cells represent a market share of 90%. The reduction of production costs is a goal of the industry, and a way to address this challenge is to develop a manufacturing process with a reduced number of steps. Considering these facts, the aim of this study is to compare and analyse the bifaciality coefficients of p-type and n-type bifacial solar cells developed with the diffusion of boron and phosphorus in a single thermal step. The co-diffusion of dopants was performed according to the patent application BR1020180085760. The sheet resistance (Rsh) and I-V characteristics of p-type and n-type bifacial solar cells produced with boron diffusion temperatures ranging from 940 970 °C were measured to determine the bifaciality coefficients. For both types of substrates, the Rsh of the emitters was higher than the Rsh of the back surface field, and the phosphorus-doped layer was affected by the boron diffusion temperature. The shortcircuit current density (Jsc) of p-type bifacial solar cells with incident irradiance on the boron-BSF was low. Consequently, the Jsc and the maximum power output bifaciality coefficients of the p-type devices were approximately 0.6, lower than those of the n-type solar cells, which were close to 1.0. The results demonstrated that the bifaciality coefficients of commercial n-type TOPCon solar cells have the potential to be improved from 0.8 to approximately 1.0.
Keywords
Bifacial solar cells, p-type and n-type solar cells, reduced thermal steps, bifaciality coefficients