BiFeO₃ perovskite-based all oxide ambient stable spectrally selective absorber coatings for solar thermal application

Enhancements in absorbance and thermal stability are essential for solar selective absorber coatings (SSACs) to convert solar energy efficiently into thermal energy. Considering the same, we investigated thin films of BiFeO3 (BFO) ternary perovskite on different metal substrates (copper, aluminum and stainless steel) for solar selective coatings using a simple and cost-effective solution-based method assisted by the spin coating process. BiFeO3 thin films coated on Cu (i.e., BFO/Cu) exhibit a high absorptance of 0.91 ± 0.03 in the UV-vis (0.2-0.8 μm) region and a low emittance of 0.12 ± 0.01 in the infrared region (2.5-25 μm). Furthermore, the detailed structural, microstructural, and optical properties are investigated and electrical impedance spectroscopy measurements are carried out on different thickness BFO-based SSACs to understand the overall impact on the spectral response. The BFO/Cu SSAC structure shows high thermal stability at 300 °C for 60 hours under ambient conditions no significant change in absorptance, but slight increase in emittance to 0.21 ± 0.01. Moreover, the corrosion characteristics of these SSACs suggest that BFO/Cu has a lower corrosion rate (0.001 mm peryear.) than that of a pristine Cu substrate, which is much larger, i.e., ∼0.058 mm per year. More interestingly, the absorptance has increased significantly to 0.94 ± 0.01, whereas the emittance has risen to 0.18 ± 0.01 after corrosion tests. These changes are attributed to the respective microstructural surface changes. Thus, the present work may lead to the development of all oxide-based highly stable SSACs for solar thermal applications.