Spectrally selective Al/AlN/Al/AlN tandem solar absorber by inline reactive ac magnetron sputtering

Abstract

Spectrally selective Al/AlN/Al/AlN tandem solar absorbers were deposited onto soda lime glass substrates using inline ac magnetron sputtering in a reactive atmosphere containing argon and nitrogen. To achieve a reproducible and homogenous deposition process, the deposition of multilayer Al/AlN/Al/AlN films under different process conditions was investigated. Two main variables, ac power and the speed of substrate movement in the chamber, were varied in the ranges of 1-10 kW and 10?47-31?4 mm s 21 respectively to obtain films with high absorption and low emittance. The effects of film thickness of different layers and deposition conditions on the optical performance of selective coatings were also studied. Structural features and surface morphology of the films were investigated by X-ray diffraction and field emission scanning electron microscopy analyses respectively. In the present study, tandem solar absorber films deposited onto glass substrate with optimised sputtering parameters can consistently achieve solar absorptance a of 0?864 and thermal emittance e of 0?03 at 80uC.

Preparation of ScAlN films as a function of sputtering atmosphere

“…Meanwhile, aluminum nitride (AlN) thin films has become a standard electronic materials for many conventional MEMS devices, especially for high-temperature piezoelectric sensors and thin film bulk-acoustic resonator (FBAR) duplex filters for its excellent combination of remarkable properties. As the piezoelectric material, it is important to enhance the piezoelectric coefficient of the AlN film [5]. However, when compared with PZT and ZnO piezoelectric thin films, AlN presents a lower electro-mechanical coupling coefficient (k t 2 ) and piezoelectric constant (d 33 ) which limits the wide application in sensors and filters.…”

Enhanced absorptance of surface-textured tungsten thin film for solar absorber

“…In solar thermal technologies, solar absorbers are crucial components that absorb and convert sunlight into thermal energy, which requires low reflectance in the solar radiation spectrum range (0.3-2.5 μm) and high reflectance in the IR range (2.5-50 μm). [1][2][3][4][5] Intrinsic absorbers, in which selectivity is an intrinsic property of the materials, are structurally more stable but optically less effective than multilayer stacks examples including metal W. 6 Tungsten (W) is an extremely interesting material due to its unique properties, like its thermal stability (T m = 3693 K), high density (ρ = 19.30 g cm −3 ), mechanical properties (H = 3.53-5.884 GPa; E = 407 GPa), wear resistance and low thermal emittance. 7 Historically, research in intrinsic absorbers has not been very productive because there are no ideal intrinsic materials, but the intrinsic material W has been finding increasing use as a component in high-temperature absorber multilayers and composite coatings.…”