We have shown that a light-concentrating core-shell monolith can be fabricated by simple colloidal self-assembly of PS nanospheres. Further, the refractive index contrast between the monolith and air can be increased by the deposition of TiO2 via ALD. The generality of these processes (nanosphere diameter, ALD layer thicknesses and material) yields significant tailorability in the optical properties of the monolith, which can be chosen to match the absorber of interest. Here, we showed that a PS-TiO2 coreshell monolith can be fabricated from these methods. The structure of the monolith was