Summary: This work describes a “high-school chemistry”-based technique for making selective solar absorbers.
Selective solar absorbers are surfaces that are black and absorb sunlight, but unlike typical black surfaces, they do not radiate and lose heat. Therefore under sunlight, these surfaces become much hotter than typical black surfaces. The heat these surfaces capture from the sun can be used for heating or boiling water, desalination and even generating electricity – so these surfaces can be quite useful.
To my knowledge, the technique for making selective solar absorbers described in this paper is one of the easiest, fastest and most tunable, but yields high optical performance (wide angle solar absorptance > 96% and hemispherical thermal emittance < 10%) nonetheless. Given its scalability, it may be promising for widespread use.