Inkjet-Printed Three-Dimensional Colloidal Photonic Crystals for Structural Coloration of Solar Cells

Large scale implementation of building-integrated photovoltaics (BIPV) requires matching the visual appearance of solar modules with other building materials. One approach is to add reflective color filters to conventional PV modules. Structural colors based on light interference are promising for this purpose, because they can produce color without parasitic light absorption, however, their angle-dependent (iridescent) appearance is unsuitable for most architectural applications and their fabrication methods ill-suited for color and pattern variation. Here, we report structural color filter fabricated by inkjet-printing three-dimensional photonic crystals (PC). A PC ink, consisting of monodispersed polystyrene nanoparticles of 200 nm diameter, was printed on a glass slide that had been treated with octadecyl-trichlorosilane (OTS) to control the droplet contact angle during drying, which was known to produce self-assembled 3-dimensional PC domes that exhibit angle-independent reflection. Measurements confirmed angle-independent cyan-colored reflection by the PC domes, but overall weak coloration. The PC color filter had 11.3 % peak reflectance at 467 nm, which caused 11 % decrease in the short-circuit current when coupled to a monocrystalline silicon solar cell. According to a theoretical analysis, increasing the surface coverage of the PC domes from 13 % to 80 % could increase the peak reflectance to 26 %.