Thermal durability of solar selective absorbers consisting of β-FeSi2 with low emissive Ag layers on stainless steel

Solar selective absorbers based on semiconducting β-FeSi2 and low-emissive Ag layers were prepared on stainless steel substrates, and the thermal durability below 650 °C was evaluated. Agglomeration and vaporization of the Ag layers were prevented by adding Ta and stacking with TaN layers, respectively. The solar absorbing layers, consisting of β-FeSi2, deteriorated at high temperatures, as a result of diffusion of Si from the silicide layers to substrates, which could be suppressed by using TaN/SiO2 layers at the interface between the stainless steel substrates and Ag layers with Ta and Si additives. The thermally stabilized solar selective absorbers achieved an averaged solar-thermal conversion efficiency of 87.0% between 300 and 650 °C. Arrhenius plots based on accelerated heating tests between 750 and 800 °C showed that the thermally stabilized absorbers were able to keep the decline in efficiency to within 1% for over 42 years at 650 °C. [Display omitted] •High temperature efficient solar-thermal conversion by β-FeSi2 on a Ag base.•High efficiency originates from a steep cut-off at the band-edge absorption.•Low emissivity originates from thermally stabilized Ag base.•Thermally stable Ag layer contained Ta additives and TaN layers.•Diffusion of Si from β-FeSi2 to stainless steel was suppressed by TaN/SiO2 layers.