How is a thermionic power converter similar to an electronic diode?

A thermionic power converter is fundamentally similar to an electronic diode because it functions as a two-electrode device that utilizes thermionic emission to facilitate the flow of electrons between a heated cathode (emitter) and a cooler anode (collector).12

In both devices, the basic physical principle involves the emission of electrons from a heated material, which then travel to a collector electrode. Just as a vacuum-tube diode permits electrons to flow from the cathode to the plate but not in the reverse direction, the thermionic converter relies on this directional movement of charge carriers to operate.1342

While a standard diode is typically used to rectify current or control signal flow in electronic circuits, a thermionic power converter is specifically designed as a heat engine that converts thermal energy directly into electrical energy. In this process, the converter uses the potential difference created by the emission of electrons to drive current through an external load.12