One of the previous attempts at that, with a "power density of a gasoline tank", according to the authors: https://en.wikipedia.org/wiki/Optoelectric_nuclear_ba

One of the previous attempts at that, with a "power density of a gasoline tank", according to the authors: https://en.wikipedia.org/wiki/Optoelectric_nuclear_battery https://en.wikipedia.org/wiki/Optoelectric_nuclear_battery