Strong Omnidirectional and Broadband Absorption of the Solar Light with Arrays of Submicrometer‐Scaled Compound Parabolic Light Concentrators

Efficient omnidirectional broadband absorption is important to various applications involving the harvest of the solar spectrum. The optical absorption dependency on oblique illumination in arrays of submicrometer‐scaled compound parabolic concentrators (CPCs) is examined. For a non‐optimized CPC array, the broadband absorption is ≈30% higher than that of a nanopillar (NP) array that is corrected for the absorption of the solar light for an angle‐of‐illumination range of 0°–80°. It is shown that enhanced absorptivity of CPC arrays, relative to the optically corrected NP array, is due to the repressed transmission for both transverse electric and transverse magnetic illumination. It is determined that the superior omnidirectional broadband absorption of a CPC array is due to strong “light bending”; in the CPC array, the optical intensity is predominantly distributed laterally, whereas in the NP array, the optical intensity is mainly directed in the vertical direction. It is shown that for the CPC array, the intensity lateral components are up to 80% higher than the lateral components in the NP array. Finally, the CPC array omnidirectional broadband absorption is governed by substantial light bending, which induces competent excitation of various asymmetric photonic states.