The performance is very impressive in comparison with devices of the same type that have been produced in the past.
The performance is not impressive in comparison with the existing alternative for converting heat into electricity, i.e. with electric generators powered by closed-cycle gas turbines or by steam turbines, which can reach a higher efficiency already at much lower temperatures and without using so expensive materials.
Therefore it is not clear whether this direction of research is worth pursuing.
Moreover, triple-junction (very expensive) solar cells with an efficiency of around 45% for the direct conversion of solar light, without passing through heat, have already been demonstrated some time ago. Due to their high cost, they must also be used with solar concentrators, but the concentrators can be much cheaper than those needed to heat something over 2000 Celsius degrees (which requires very precise focusing).
The performance is not impressive in comparison with the existing alternative for converting heat into electricity, i.e. with electric generators powered by closed-cycle gas turbines or by steam turbines, which can reach a higher efficiency already at much lower temperatures and without using so expensive materials.
Therefore it is not clear whether this direction of research is worth pursuing.
Moreover, triple-junction (very expensive) solar cells with an efficiency of around 45% for the direct conversion of solar light, without passing through heat, have already been demonstrated some time ago. Due to their high cost, they must also be used with solar concentrators, but the concentrators can be much cheaper than those needed to heat something over 2000 Celsius degrees (which requires very precise focusing).