Chromatic sunshade cladding unit

A sunshade cladding unit comprising a plurality of lamellae each having a substantially flat and elongated conformation along a respective development axis (B), and a structure supporting the lamellae configured to support the plurality of lamellae in a condition of parallel and spaced apart lamellae along a direction orthogonal to the development axes (B), the structure supporting the lamellae being configured to support each of the plurality of lamellae in a rotatable manner about a rotation axis parallel to or coincident with its development axis (B), wherein each lamella of the plurality of lamellae includes at least one surface portion which comprises at least

• a reflective layer having at least one reflective surface, and
• a chromatic diffusion layer having a first surface proximal to the reflective surface and a second surface, opposite and substantially parallel to the first, configured to be illuminated by incident light,
• wherein the chromatic diffusion layer comprises a nano-pillar or nano-pore structure in a first material having a first refractive index (n1), immersed in a second material having a second refractive index (n2) different from the first (n1), in which the first and second materials are substantially non-absorbing or transparent to electromagnetic radiations with wavelength comprised in the visible spectrum,
• wherein a ratio (nM/nm) between a higher refractive index (nM) and a lower refractive index (nm) chosen between the first (n1) and the second (n2) refractive indexes is between 1.05 and 3,
• wherein the nano-pillars or nano-pores locally have a development along a main direction not parallel to the first surface and to the second surface of the chromatic diffusion layer, and the nano-pillar or nano-pore structure is characterized by a plurality of geometric parameters comprising a pillar diameter or pore diameter (dp), a pillar length or pore length (Ip) along said non-parallel direction, a surface density of nano-pillars or nano-pores (Dp) and a porosity (Pp) of the nano-pillar or nano-pore structure, and wherein the plurality of geometric parameters is configured to provide a higher regular reflectance for wavelengths of the incident light in the range of red with respect to wavelengths of the incident light in the range of blue and a higher diffuse reflectance for wavelengths of the incident light in the range of blue with respect to wavelengths of the incident light in the range of red.