Lightweight Photonic Cooler with Multi-Layered Thin Film IR Filters and Anti-Dust Properties for PV Applications in Desert Environments

The present research is dedicated to the design and fabrication of advanced multi-stacked thin-film structures composed of alternating metal-oxide and metallic layers. These engineered coatings are conceived as multifunctional photonic coolers, offering a combination of near-infrared (NIR) filtering, anti-dust, and anti-reflective properties that make them highly attractive for deployment in energy-intensive environments. The optimized configuration consists of three key components: titanium oxide (TiOx) as the outermost layer, nickel oxide (NiO) as an intermediate buffer, and silver (Ag) as the reflective hot-mirror layer. Each material in this architecture serves a distinct optical and functional role. The layers were deposited using thermal electron-beam (e-beam) evaporation under a controlled oxygen atmosphere, with a continuous vacuum environment maintained throughout the process to ensure dense, defect-free growth and reproducible film quality. One of the notable characteristics of the TiOx top layer is its inherent super-hydrophilicity. This property imparts both selfcleaning and anti-dust functionalities, critical for outdoor applications in desert climates where soiling can drastically reduce optical efficiency. In parallel, the multi-layer stacking strategy leverages the contrasting refractive indices of constituent oxides to fine-tune the spectral response. Low-refractive-index TiOx, when paired with high-refractive-index oxides such as NiO or molybdenum oxide (MoOx), creates constructive interference effects that enhance visible light transmission while simultaneously suppressing unwanted infrared radiation. Experimental results confirmed that bilayer combinations such as MoOx/TiOx and NiO/TiOx exhibited superior transmittance in the visible spectrum compared to single TiOx films, thereby optimizing light harvesting in photovoltaic and optical applications. The inclusion of a reflective metallic layer (Ag or, alternatively, Al) further enhanced performance, acting as an efficient hot-mirror with a wavelength cutoff beginning at ~800 nm. Beyond this threshold, the structure demonstrated the ability to reflect more than 70% of incident IR radiation, thereby effectively mitigating heat accumulation. This carefully engineered multi-stack thin-film structure not only provides efficient IR filtering but also functions simultaneously as an anti-reflective coating for visible light and as an anti-soiling surface layer. These multifunctional attributes significantly extend its commercial potential, particularly for integration into energy-efficient building envelopes, smart glazing, and large-scale photovoltaic systems operating under harsh and dusty environmental conditions. Furthermore, the reliance on scalable deposition techniques, such as e-beam evaporation, underscores the feasibility of adapting this approach for industrial-scale manufacturing. In sum, the multi-layer metal-oxide/metal-oxide/metal photonic cooler represents a versatile, durable, and scalable solution for managing the solar spectrum, mitigating heat, enhancing light utilization, and resisting environmental degradation. Its multifunctionality positions it as a promising candidate for next-generation energy-saving technologies in desert and other extreme climates.