Abstract
Interdigitated back contact (IBC) n-type silicon solar cells with a different front surface layer doping concentration were fabricated and studied and the influence of the front surface doping level was analyzed via simulation (PC1D). The IBC cells were processed by industrially feasible technologies including laser ablation and screen printing; photolithography was not used. A maximum efficiency of up to 20.88% was achieved at an optimal front surface field (FSF) peak doping concentration of 4.8 × 1019 cm−3 with a sheet resistance of approximately 95 Ω/square, corresponding to Jsc = 40.05 mA/cm2, Voc = 671 mV and a fill factor of 77.70%. The effects of the front surface doping level were studied in detail by analyzing parameters related to carrier transmission mechanisms such as minority carrier concentration, minority carrier lifetime and the saturation current density of the FSF (J0e). The influence of the front surface recombination velocity (FSRV) on the performance of IBC solar cells with different FSF layer doping concentrations was also investigated and was verified by examining the variation in the minority carrier density as a function of the distance from the front surface. In particular, the impact of the FSF doping concentration on the Jsc of the IBC cells was clarified by considering carrier transmission mechanisms and the charge-collection probability. The trends revealed in the simulations agreed with the corresponding experimental data obtained from the fabricated IBC solar cells. This study not only verifies that the presented simulation is a reasonable and reliable guide for choosing the optimal front surface doping concentration in industrial IBC solar cells but also provides a deeper physical understanding of the impact that front surface layer doping has on the IBC solar cell performance considering carrier transmission mechanisms and the charge-collection probability.
Highlights
Interdigitated back contact (IBC) n-type solar cells [1,2] have attracted much attention in recent years
Poor front surface passivation leads to a decrease in the diffusion length of the minority carriers that results in a significant recombination of the photogenerated carriers generated near the cell front surface before they contribute to the electrical performances of the solar cell
The minority carrier density in the base was highest in the best efficiency cell and it increased as the recombination in the doped front surface decreased
Summary
Interdigitated back contact (IBC) n-type solar cells [1,2] have attracted much attention in recent years. Their high efficiency reduces the manufacturing cost by increasing the amount of electric power generated by each photovoltaic (PV) system [3,4,5]. When compared with the front contact cells, the first and most important advantage of the IBC solar cells is the complete elimination of optical shading toward the front side This can be achieved by transferring the metal grids to the rear surface, which is typically responsible for increasing the short-circuit current density by 4–8% [6,7].
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