Enhanced and Selective Absorption of Molybdenum Nanostructured Surfaces for Concentrated Solar Energy Applications

Abstract

Surfaces of commercial molybdenum (Mo) plates have been textured by fs-laser treatments with the aim to form low-cost and efficient solar absorbers and substrates for thermionic cathodes in Concentrated Solar Power conversion devices. Morphological (SEM and AFM), optical (spectrophotometry), and structural (Raman spectroscopy) properties of the samples treated at different laser fluences (from 1.8 to 14 J/cm2) have been characterized after the laser treatments and also following long thermal annealing for simulating the operating conditions of thermionic converters. A significant improvement of the solar absorptance and selectivity, with a maximum value of about four times higher than the pristine sample at a temperature of 800 K, has been detected for sample surfaces treated at intermediate fluences. The effects observed have been related to the light trapping capability of the laser-induced nanotexturing, whereas a low selectivity, together with a high absorptance, could be revealed when the highest laser fluence was employed due to a significant presence of oxide species. The ageing process confirms the performance improvement shown when treated samples are used as solar absorbers, even though, due to chemical modification occurring at the surface, a decrease of the solar absorptance takes place. Interestingly, the sample showing the highest quantity of oxides preserves more efficiently the laser texturing. The observation of this behaviour allows to extend the applicability of the laser treatments since, by further nanostructuring of the Mo oxides, it could be beneficial also for sensing applications.

Highly Regular LIPSS on Thin Molybdenum Films: Optimization and Generic Criteria

“…It should be noted that, upon ablation in air, an oxide layer can be formed on the top of the ablated metal. However, according to Santagata et al [ 3 ], this effect becomes important for molybdenum at fluences above 10 J/cm , which is much higher than applied in our experiments. Indeed, Raman analysis shows only some traces of MoO (not presented here).…”

“…In recent years, the fabrication of highly regular laser-induced periodic surface structures (HR-LIPSSs) over large areas using ultrashort laser pulses has been a topic of interest due to their scientific and industrial applications [ 1 , 2 , 3 ]. Self-replication of the LIPSS makes it possible to cover material surfaces with ripples by scanning the laser beam with appropriate parameters [ 1 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ].…”

Homogeneous Nanostructuring of a Molybdenum Surface by Dual-Color Correlated Femtosecond Laser Irradiation for Solar Absorber Applications

“…It was recently reported that the LIPSS−Mo surface pair can improve the solar spectral selectivity by a maximum of about 4 times. 28 With the significant performance improvements on solar absorptance and selectivity as well as the high thermal and mechanical stability, the LIPSS−Mo surface pair is the most promising candidate for low-cost, efficient, and high-temperature selective solar absorbers in concentrated solar energy devices. Besides, the LIPSS−Mo surface pair enables other numerous potential applications in antifriction, antibacteria, biocompatibility, superhydrophobicity, etc.…”

“…The dual-color correlated laser nanostructuring not only provides a strategy for manufacturing structures on metals with 100 nm feature sizes but also renders new functions by altering its properties in optics, mechanics, chemistry, and biology. The nanostructured Mo surface not only displays performance improvements on solar absorptance and selectivity, which are beneficial for efficient solar absorber applications, , but also enables other potential applications in antifriction, antibacteria, biocompatibility, superhydrophobicity, etc.…”

Surface Nanotexturing of Boron-Doped Diamond Films by Ultrashort Laser Pulses

“…It is widely known, in fact, that mechanical strains can alter the electronic, optical, and mechanical properties of 2D crystals [ 9 ] and that “elastic strain engineering” is becoming a useful tool for bulk materials as well [ 10 ]. On the other hand, chemical modifications can be laser-induced (e.g., superficial oxidation [ 11 ]), or new chemical functional groups can be introduced post-irradiation via surface adsorption [ 12 ]. In this context, characterization by Raman spectroscopy is useful for assessing possible chemical modifications.…”