Dual‐Layer Thin Film Coating for Solar Energy Harvesting

Abstract The efficiency of photovoltaic (PV) cells is significantly compromised by optical losses, surface contamination, and heat‐induced degradation. While antireflective (AR) and self‐cleaning coatings partially address these issues, their limited durability and inability to concurrently optimize optical, thermal, and mechanical performance hinder practical use. Here, we report a sol–gel spin‐coated dual‐layer thin film that decouples and integrates distinct functionalities: a TiO 2 /SiO 2 top‐layer for AR performance and self‐cleaning, and a ZnO/SiO 2 bottom‐layer for near‐infrared (NIR) reflection. A TiO 2 /SiO 2 top‐layer (C1) and a ZnO/SiO 2 bottom‐layer (C2) coated glass exhibited an average visible light transmittance of 94.1%, representing an increase of approximately 3.7% compared to bare glass via refractive index matching and optical interference, and reduces operating temperatures by 6 °C under IR irradiation—translating to a ∼3% PV efficiency improvement. Interface engineering at the TiO 2 /SiO 2 boundary enhances surface hydroxylation, enabling super‐hydrophilicity (7.5° water contact angle (WCA)) and photocatalytic degradation of organic contaminants. Mechanical durability, validated by pencil hardness (5H/4H) and adhesion tests (4B/5B), exceeds industrial standards for PV modules. By synergizing optical, thermal, and self‐cleaning properties in a scalable coating, this work offers a practical pathway to enhance solar energy conversion in real‐world environments.