Black silicon solar cells with interdigitated back-contacts achieve 22.1% efficiency

Abstract

The nanostructuring of silicon surfaces—known as black silicon—is a promising approach to eliminate front-surface reflection in photovoltaic devices without the need for a conventional antireflection coating. This might lead to both an increase in efficiency and a reduction in the manufacturing costs of solar cells. However, all previous attempts to integrate black silicon into solar cells have resulted in cell efficiencies well below 20% due to the increased charge carrier recombination at the nanostructured surface. Here, we show that a conformal alumina film can solve the issue of surface recombination in black silicon solar cells by providing excellent chemical and electrical passivation. We demonstrate that efficiencies above 22% can be reached, even in thick interdigitated back-contacted cells, where carrier transport is very\ud sensitive to front surface passivation. This means that the surface recombination issue has truly been solved and black silicon solar cells have real potential for industrial production. Furthermore, we show that the use of black silicon can result in a 3% increase in daily energy production when compared with a reference cell with the same efficiency, due to its better angular acceptance.Peer ReviewedPostprint (author's final draft

Realization of Quasi‐Omnidirectional Solar Cells with Superior Electrical Performance by All‐Solution‐Processed Si Nanopyramids

“…For heterojunction solar cells, from Figure 4d, it can be seen that the QE spectra of the SiMPs‐textured solar cell decrease gradually with increasing θ. Differently, Figure 4e shows that when the θ is smaller than 45°, the QE spectra of the SiNPs‐textured solar cell drop very slightly with increasing θ, but when the θ is larger than 60°, it turns to drop rapidly with increasing θ, which is similar to that of Si nanopillars‐textured solar cell 6. For better comparison, we have also plotted the QEs at 900 nm of the both kinds of solar cells as a function of θ, as shown in Figure 4f.…”

“…Though photovoltaic sun tracking system is effective to solve the problem induced by the changed θ, it is costly and difficult to work precisely for more than 20–25 years of module lifetime 1. In recent years, there are lots of reports demonstrating that Si nanostructures possess outstanding broadband and omnidirectional antireflection ability, which are promising to be adopted in solar cells to form omnidirectional solar cells for enhancing electric energy output over broad θ 2, 3, 4, 5, 6, 7, 8, 9. For example, Spinelli et al2 have reported that Si nanocylinder arrays can effectively suppress reflection over the wide θ of 0°–60°.…”

“…For example, Spinelli et al2 have reported that Si nanocylinder arrays can effectively suppress reflection over the wide θ of 0°–60°. Savin et al6 even demonstrated that Si nanopillars textured solar cell brings 3% higher in daily energy production as compared to the conventional Si micropyramids (SiMPs)‐textured solar cell, which benefits from its better angular acceptance. Hence, considerable efforts have been focused on integrating Si nanostructures into various solar cells, such as diffused homojunction cells,10, 11, 12 heterojunction cells,13, 14 photo‐electrochemical cells,15 hybrid cells,16, 17, 18 carrier‐selective contact cells,19 and ultrathin crystalline Si (c‐Si) cells 20…”

“…Recently, through passivating the surface by thermal SiO 2 , SiO 2 /SiN x :H dual layers, or atomic layer deposited Al 2 O 3 layer, ηs approaching or higher than 20% have been demonstrated on Si nanostructures‐textured solar cells thanks to the excellent passivation effect of these dielectric layers 6, 22, 23. Nevertheless, when compared to their conventional SiMPs‐textured counterparts, the nanostructures‐textured solar cells still suffer from higher carrier recombination and thus have lower open‐circuit voltage ( V OC ).…”

PV cells electrical parameters measurement

“…On that account, a real PV cell is measured at standard conditions, ie in the lab using solar simulator equipment, at known both irradiance intensity and standard spectral distribution specified by air mass AM1.5 Global filter usually at 1000 W/m 2 light power. [1][2][3][4] Based on theoretical approach with respect to experiments, this paper analyses I − V electrical parameters acquisition needs when measuring a PV silicon cell, as well as P − V and efficiency estimation, to reveal troubleshooting and accuracy of these procedures.…”