Quasicrystalline-structured light harvesting nanophotonic silicon films on nanoimprinted glass for ultra-thin photovoltaics

We present nanophotonic light harvesting crystalline silicon c Si thin films on glass exhibiting ten fold transversely quasicrystalline lattice geometry on 6 x 8 mm2 area. The c Si architectures with a nearest neighbor distance of 650 nm are fabricated by nanoimprinting the desired quasicrystalline geometry into sol gel coated glass substrates followed by Si deposition of 240 nm to 270 nm thickness, self organized solid phase crystallization and selective chemical etching. Broadband absorption measurements on these quasicrystalline structured c Si architectures yield a very significant improvement in light trapping in the near infrared regime and an enhanced light coupling due to a graded index effect in comparison to the unstructured sample. The average value of maximum achievable short circuit current density jsc, max of solar cells with such quasicrystallinestructured c Si absorber geometry 19.3 mA cm2 is more than double in comparison to the jsc, max of unstructured planar films of the same thickness 9.3 mA cm2 and remains stable for light incident angles up to 60 . In comparison to a 320 nm thick c Si film on textured ZnO Al substrate as widely used for light trapping in amorphous microcrystalline Si thin film photovoltaics, still a 65 increased jsc, max is observable for the presented quasicrystalline c Si structures. The nanophotonic light trapping efficiency of these transversely quasicrystalline c Si nanoarchitectures is among the highest values for experimentally realized structures, revealing their promising influence for broadband and isotropic light trapping for economically viable and efficient ultra thin solar cells