Spectrally Selective Coatings for Solar Thermal Applications

Spectrally selective coatings are engineered surfaces that maximise absorption of the solar spectrum while minimising thermal re-radiation losses. By tailoring optical properties across ultraviolet, visible and infrared bands, these coatings enable high solar-to-heat conversion efficiencies at both moderate and elevated temperatures. Key design approaches include multilayer dielectric–metal stacks, cermet composites, intrinsic narrow-bandgap semiconductors and hierarchically structured nanoceramics. Recent advances focus on robust materials capable of enduring thermal cycling beyond 600 °C without significant degradation, together with scalable deposition techniques suited to large-area receivers. Such coatings underpin concentrating solar power plants, solar-driven desalination units and photothermal water purification systems, and contribute to global efforts in decarbonising industrial heat and distributed energy applications.

Research from Nature Portfolio

Recent studies have introduced a narrow‐bandgap semiconductor thin film as an intrinsically selective solar absorber. The material exhibits broadband solar absorptance approaching unity and low mid-infrared emissivity, yielding a record intrinsic selectivity ratio and surface temperatures above 100 °C under one-sun illumination. Demonstrations include efficient solar-water evaporation rates exceeding 1.4 kg m⁻² h⁻¹. In parallel, a multilayer semiconductor–dielectric architecture has been shown to achieve over 75% solar absorptance with thermal emissivity below 5%, enabling stagnation temperatures above 225 °C under unconcentrated sunlight. This work highlights simple fabrication routes and potential for mid-temperature solar thermal systems to reach 300 °C without optical concentrators.

Spectrally Selective Coatings for Solar Thermal Applications publication trend

The graph below shows the total number of articles in spectrally selective coatings for solar thermal applications across all publications each year (not limited to Nature Index journals).

Technical terms

Spectral selectivity: The ratio of solar absorptance to thermal emissivity, indicating how well a coating absorbs sunlight while suppressing heat loss.

Solar absorptance: The fraction of incident solar radiation absorbed by a surface across the solar spectrum.

Thermal emissivity: The efficiency with which a material emits thermal radiation at infrared wavelengths compared to a blackbody.

High-entropy material: A multicomponent alloy or compound designed to stabilise unique phases and enhance thermal and chemical resilience.

Cermet: A composite of ceramic and metallic phases combining high temperature stability with tailored optical properties.

References

1. High‐efficiency solar selective absorber: Using the high‐entropy nitride MoTaTiCrN nanoceramics as a perspective strategy. EcoEnergy (2024).
2. Unraveling the optoelectronic properties of CoSbx intrinsic selective solar absorber towards high-temperature surfaces. Nature Communications (2023).
3. Titania‐Based Coral‐Structured Solar Absorber Coating with Improved Scalability and Durability at High Temperature. Advanced Science (2024).
4. Semiconductor-based Multilayer Selective Solar Absorber for Unconcentrated Solar Thermal Energy Conversion. Scientific Reports (2017).
5. Review of the spectrally selective (CSP) absorber coatings, suitable for use in SHIP. Solar Energy Materials and Solar Cells (2022).