We report what is to our knowledge the first observation of the effect of parallel-to-interface-refraction (PIR) in a three-dimensional, simple-cubic photonic-crystal. PIR is an acutely negative refraction of light inside a photonic-crystal, leading to light-bending by nearly 90 deg over broad wavelengths (). The consequence is a longer path length of light in the medium and an improved light absorption beyond the Lambertian limit. As an illustration of the effect, we show near-unity total absorption () in and an average absorption of over for our -Si:H photonic-crystal sample of an equivalent bulk thickness of . Furthermore, we have achieved an ultra-wide angular acceptance of light over . This demonstration opens up a new door for light trapping and near-unity solar absorption over broad s and wide angles.
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