Over 65% sunlight absorption in a 1 μm Si slab with hyperuniform texture

Abstract

Thin, flexible and invisible solar cells will be an ubiquitous technology in the near future. Ultrathin crystalline silicon (c-Si) cells capitalise on the success of bulk silicon cells while being light-weight and mechanically flexible, but suffer from poor absorption and efficiency. Here we present a new family of surface texturing, based on correlated disordered hyperuniform patterns, capable of efficiently coupling the incident spectrum into the silicon slab optical modes. We experimentally demonstrate 66.5% solar light absorption in free-standing 1 µm c-Si layers by hyperuniform nanostructuring. The absorption equivalent photocurrent derived from our measurements is 26.3 mA/cm2, which is far above the highest found in literature for Si of similar thickness. Considering state-of-the-art Si PV technologies, the enhanced light trapping translates to a record efficiency above 15%. The light absorption can potentially be increased up to 33.8 mA/cm2 by incorporating a back-reflector and improved anti-reflection, for which we estimate a photovoltaic efficiency above 21% for 1 µm thick Si cells.

Scalable Disordered Hyperuniform Architectures via Nanoimprint Lithography of Metal Oxides

“…A full assessment of the optical properties of these metal oxides-based dHU nanoarchitectures goes beyond the aim of this work. However, our results support the anti-reflective effect obtained with this kind of materials, as also recently reported by other groups 15,22 . Thus, the ARC effects shown here are potentially important for devices obtained via sol-NIL, especially considering the scalability of the dewetting approach to produce hard masters and the ease of implementation of the overall process.…”

“…The scattering is redistributed in a ring with a maximal intensity at about k ∥ ∼ ±3.4 μm –1 with respect to the specular reflection peak. Thus, the scattering ring in the far-field shifts according to the incidence angle of the excitation laser, as expected for these kinds of disordered structures [ I ring ( k ∥ ) = S ( k ∥ – k in ) where k in is the projection on the plane of the sample of the wavevector of the incident radiation] . The same measurement performed on a titania-based replica of the master shows exactly the same behavior with the ring at k ∥ ∼ ±3.4 μm –1 degrees and an overall lower scattering intensity (Figure a).…”

“…Artificial structures, such as waveguide polarizers, lasers, metalenses, photonic band gaps for light propagation, − plasmonic metasurfaces, and efficient light trapping in thin Si films are recent examples of dHU systems, typically obtained via top-down fabrication methods or hybrid self-assembly and top-down . Nevertheless, dHU systems can be, in principle, obtained by self-assembly, exploiting advection, emulsions, block copolymer assembly, and sedimentation. , Other remarkable examples of dHU materials are those obtained via spontaneous pattern formation in systems following Swift–Hohenberg , and Cahn–Hilliard dynamics (respectively, describing wrinkling and phase separation via spinodal decomposition) as recently pointed out by Ma and co-workers. , These spontaneous phenomena are mainly observed in liquid and soft materials.…”

Light trapping in thin silicon solar cells: A review on fundamentals and technologies

“…88,89 What is to date the record absorption within 1-μm-thick crystalline silicon and would correspond to an equivalent short-circuit density of 26.3 mA/cm 2 was achieved with a hyperuniform texture. 90 A further approach to achieve enhanced absorption with nonperiodic nanostructures is the creation of a Fabry-Pérot cavity with the absorber material lying within this cavity and either metals or dielectric thin films effectively acting as mirrors. 91,92 This approach is based on the principle of multi-beam interference and therefore has inherently narrow wavelength response.…”

Photonics for Photovoltaics: Advances and Opportunities

“…Since periodic arrangement of scatterers generally works well only at discrete wavelengths and specific angles of incidence, engineered disorder has been explored to ensure that the spectrum of scattering wavevectors matches well with that of the waveguide modes of the absorber thin film. 24 − 30 By tailoring the resonant scattering cross sections of the scattering geometries, light trapping can be optimized to match with the optical spectral range near the semiconductor bandgap. Intense research is going on to investigate what spatial frequency distributions in the scattering pattern, such as, for example, hyperuniform distributions, are best tailored for optimum light trapping in thin layers.…”