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Monocrystalline Si (c‐Si) solar cells with passivating contacts based on doped polycrystalline Si (poly‐Si) on ≈2.0 nm silicon oxide (SiOx) require >1000 °C thermal processing to create conducting pinholes in the SiOx layer. However, this high thermal budget can induce bulk defects in the Czochralski c‐Si wafers used as the cell absorber layer. In this work, it is demonstrated that pinholes can instead be created using metal‐assisted chemical etching on planar or textured morphologies, at room temperature. This wet process creates up to 200 nm wide conducting pinholes that are directly observed with transmission electron and atomic force microscopies. High‐performance hole‐selective poly‐Si/SiNy/SiOx and electron‐selective poly‐Si/SiOx passivating contacts are fabricated and implemented in laboratory‐scale solar cells. This process development significantly broadens the range of passivation layer materials, their thicknesses, and surface morphologies, which enables the design of poly‐Si contacts with superior passivating quality. [ABSTRACT FROM AUTHOR]

We use capacitance techniques to directly measure the Fermi level at the crystalline/amorphous interface in n-type silicon heterojunction solar cells. The hole density calculated from the Fermi level position and the inferred band-bending picture show strong inversion of (n)crystalline silicon at the interface at equilibrium. Bias dependent experiments show that the Fermi level is not pinned at the interface. Instead, it moves farther from and closer to the crystalline silicon valence band under a reverse and forward bias, respectively. Under a forward bias or illumination, the Fermi level at the interface moves closer to the crystalline silicon valence band thus increases the excess hole density and band bending at the interface. This band bending further removes majority electrons away from the interface leading to lower interface recombination and higher open-circuit voltage. [ABSTRACT FROM AUTHOR]

We characterize the optical and carrier-collection physics of multi-scale textured p-type black Si solar cells with conversion efficiency of 17.1%. The multi-scale texture is achieved by combining density-graded nanoporous layer made by metal-assisted etching with micron-scale pyramid texture. We found that (1) reducing the thickness of nanostructured Si layer improves the short-wavelength spectral response and (2) multi-scale texture permits thinning of the nanostructured layer while maintaining low surface reflection. We have reduced the nanostructured layer thickness by 60% while retaining a solar-spectrum-averaged black Si reflectance of less than 2%. Spectral response at 450 nm has improved from 57% to 71%. [ABSTRACT FROM AUTHOR]

We study optical effects and factors limiting performance of our confirmed 16.8% efficiency “black silicon” solar cells. The cells incorporate density-graded nanoporous surface layers made by a one-step nanoparticle-catalyzed etch and reflect less than 3% of the solar spectrum, with no conventional antireflection coating. The cells are limited by recombination in the nanoporous layer which decreases short-wavelength spectral response. The optimum density-graded layer depth is then a compromise between reflectance reduction and recombination loss. Finally, we propose universal design rules for high-efficiency solar cells based on density-graded surfaces. [ABSTRACT FROM AUTHOR]

We present progress to develop low-cost interdigitated back contact solar cells with pc-Si/SiO 2 /c-Si passivated contacts formed by plasma immersion ion implantation (PIII). PIII is a lower-cost implantation technique than traditional beam line implantation due to its simpler design, lower operating costs, and ability to run high doses (1E14–1E18 cm −2 ) at low ion energies (20 eV–10 keV). These benefits make PIII ideal for high throughput production of patterned passivated contacts, where high-dose, low-energy implantations are made into thin (20–200 nm) a-Si layers instead of into the wafer itself. For this work symmetric passivated contact test structures (~100 nm thick) grown on n -Cz wafers with pH 3 PIII doping gave implied open circuit voltage (iV oc ) values of 730 mV with J o values of 2 fA/cm 2 . Samples doped with B 2 H 6 gave iV oc values of 690 mV and J o values of 24 fA/cm 2 , outperforming BF 3 doping, which gave iV oc values in the 660–680 mV range. Samples were further characterized by SIMS, photoluminescence, TEM, EELS, and post-metallization TLM to reveal micro- and macro-scopic structural, chemical and electrical information. [ABSTRACT FROM AUTHOR]