Keratin-Based Skin-Tone Camouflage Coating for Aesthetic Integration of Perovskite Solar Cells

Perovskite solar cells (PSCs) offer high power conversion efficiency and low-cost fabrication, yet their use in wearable and consumer-facing technologies is limited by aesthetic constraints. This study introduces keratin-based coatings as skin-tone camouflage layers that preserve photovoltaic performance. Inspired by the stratum corneum, three formulations are developed: pure keratin (KER), keratin–melanin (KML), and keratin–KerMel (KKM), the latter incorporating synthetic melanin-mimetic particles. These coatings may serve as UV-protective top layers for PSCs. Characterization revealed that KKM exhibited nanoscale uniformity and enhanced durability, contributing to superior light management. KML showed the strongest UV-blocking capacity but reduced transparency, while KER offered high transparency with limited protection. Mechanical testing confirmed the robustness of all coatings, with tensile strengths of ≈3 MPa (KML), ≈2.5 MPa (KKM), and ≈1.7 MPa (KER). The KKM coating achieved a power conversion efficiency of ≈12%, compared to ≈15% in the uncoated reference, and outperformed both KER (≈10%) and KML (≈8%). Stability testing showed KKM retained ≈79% of its initial performance after 14 days, exceeding KER and KML, though slightly below the uncoated device. These results highlight keratin-based coatings as viable materials for merging functionality and aesthetics in renewable energy and biomedical applications.