They've built those in the lab decades ago [0]. I don't know what the large drawback is that prevents them from being more widely used. In the thermophotovolta

They've built those in the lab decades ago [0]. I don't know what the large drawback is that prevents them from being more widely used. In the thermophotovoltaic case they were looking at emitter temperatures between 1,200 and 1,350 K. [0] https://sci-hub.se/https://doi.org/10.1063/1.1867178 https://sci-hub.se/https://doi.org/10.1063/1.1867178 ("Thermophotovoltaic Converter Performance for Radioisotope Power Systems", 2005)