Durability evaluation of structural colored PV minimodule by stress tests for BIPV applications

Building-integrated photovoltaics (BIPV) offers a promising approach for incorporating solar modules directly into architectural structures. To visually harmonize with surrounding environments, structural coloring using dielectric multilayers is often applied to PV modules. For practical implementation, maintaining both visual and electrical stability of colored PV modules is essential. In this study, we evaluated the long-term durability of colored PV minimodules, featuring SiO₂/TiO₂ dielectric multilayers coated on the outer surface of the cover glass, through accelerated stress tests in accordance with IEC61215 and IEC61646 standards, including ultraviolet exposure, damp heat (DH) and thermal cycling. The results demonstrated that the structural color layers exhibit sufficient resistance to environmental stress and did not compromise the overall durability of the PV minimodules. However, a slight expansion (approximately 2–3 %) of the SiO₂ layers was observed during the initial DH test, causing minor color variations that were nearly imperceptible. To suppress this color instability a 40-h DH pre-stabilization treatment was applied. The pre-stabilized SiO₂ layers showed minimal thickness variation (within ±1 %) before and after testing. Colored PV minimodules with this treatment retained consistent color (CIEDE2000 < 4) and showed less than 2 % reduction in short-circuit density, confirming that the pre-stabilization process effectively improves stability without adverse effects.