Approaching conversion limit with all-dielectric solar cell reflectors

Abstract

Metallic back reflectors has been used for thin-film and wafer-based solar cells for very long time. Nonetheless, the metallic mirrors might not be the best choices for photovoltaics. In this work, we show that solar cells with all-dielectric reflectors can surpass the best-configured metal-backed devices. Theoretical and experimental results all show that superior large-angle light scattering capability can be achieved by the diffuse medium reflectors, and the solar cell J-V enhancement is higher for solar cells using all-dielectric reflectors. Specifically, the measured diffused scattering efficiency (D.S.E.) of a diffuse medium reflector is >0.8 for the light trapping spectral range (600nm-1000nm), and the measured reflectance of a diffuse medium can be as high as silver if the geometry of embedded titanium oxide(TiO(2)) nanoparticles is optimized. Moreover, the diffuse medium reflectors have the additional advantage of room-temperature processing, low cost, and very high throughput. We believe that using all-dielectric solar cell reflectors is a way to approach the thermodynamic conversion limit by completely excluding metallic dissipation.

A 19.9%-efficient ultrathin solar cell based on a 205-nm-thick GaAs absorber and a silver nanostructured back mirror

“…Parasitic optical losses contain absorption in the window layer (dJ=1.3 mA/cm²), in the BSF (dJ=1.2 mA/cm²), in the Ag mirror (dJ=2.7 mA/cm²) and due to reflection (dJ=1.1 mA/cm²). Parasitic absorption in the metallic reflector can be avoided through a combination of high-index-contrast gratings with all-dielectric or hybrid dielectric/metallic mirrors(36,37). The stack of semiconductor heterostructures needs further optimization to reduce the thickness of the AlInP and AlGaAs layers and improve collection of photogenerated carriers in these layers.…”

Enhancing Light Harvesting in Dye-Sensitized Solar Cells through Mesoporous Silica Nanoparticle-Mediated Diffuse Scattering Back Reflectors

“…The result is a diffuse back reflector that recycles photons and confines them within the system, improving the absorption of light [29]. Dielectric reflectors have shown superior diffuse scattering efficiency compared to metallic reflectors, with the advantage of lower cost [30]. Since DSSCs perform exceptionally well under diffuse light conditions [31], the enhanced harvesting of ambient light owing to MSN reflectors makes them suitable for low-light and indoor applications.…”