Semiconductor-dielectric-metal solar absorbers with high spectral selectivity

• Published in: Solar energy materials and solar cells Vol. 240; no. C; p. 111735
• Main Authors: Tervo, Eric J., Steiner, Myles A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.06.2022; Elsevier BV; Elsevier
• Subjects: Absorptance; Absorption; Absorptivity; Blackbody; concentrating solar power; Dielectrics; Emittance; Energy conversion; High temperature; Irradiance; Magnesium fluorides; Optical properties; Photonic band gaps; Photons; Photovoltaic cells; selective absorber; Selectivity; Silver; SOLAR ENERGY; Solar energy absorbers; Solar heating; solar thermal energy conversion; Thermal emission; Thermal energy; Wavelength; Wavelengths
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2022.111735

An ideal solar thermal absorber has a sharp transition between high and low absorptance at the wavelength where the blackbody emissive power begins to exceed the solar irradiance. However, most real selective absorbers have a fairly broad transition, leading to both solar absorption and thermal emission losses. Here, we model, fabricate, and characterize a highly selective semiconductor-dielectric-metal (Ga0.46In0.54As – MgF2 – Ag) solar absorber with an extremely sharp transition from high to low absorptance. The thin semiconductor serves as a selective filter, absorbing photons with wavelengths shorter than the bandgap and transmitting those with longer wavelengths. The highly reflective dielectric-metal rear mirror allows the structure to have very low emittance for longer wavelengths. These characteristics provide the absorber with a measured solar absorptance >91% below the bandgap wavelength and infrared emittance <5% at 100 °C above the bandgap wavelength. This transition wavelength can be tuned by modifying the semiconductor composition, and modeling indicates that the absorber's optical properties should be stable at high temperatures, making the structure a good candidate for unconcentrated to highly concentrated solar thermal energy conversion. •Fabricated absorbers feature high solar absorptance and low thermal emittance.•A tunable, sharp transition wavelength is achieved with a GaInAs absorber layer.•Modeling indicates that optical properties should be stable at high temperatures.•Appropriate for a variety of applications from high to low optical concentration.