An apparatus includes an emitter electrode including a phosphorus doped diamond layer with low work function. The apparatus further includes a collector electrode and a vacuum gap disposed between the emitter and the collector. The collector has a work function of 0.84 eV or less.

Embodiments relate to a method in which electrical energy is supplied to a heat generating source to convert the electrical energy to heat. A thermal energy harvesting thermionic device proximal to the heat generating source to receive the heat from the heat generating source is heated and an electrical output is generated. The thermal energy harvesting thermionic device includes at least a cathode, an anode spaced from the cathode to provide an inter-electrode gap between the cathode and the anode, and a plurality of nanoparticles suspended in a fluid medium contained in the inter-electrode gap. The temperature of the thermal energy harvesting thermionic device is monitored, and a source of the electrical energy is activated to supply the electrical energy to the heat generating source in response to a change in the temperature of the thermal energy harvesting thermionic device. Also provided are related apparatus.

Disclosed embodiments include vacuum electronic devices, methods of operating a vacuum electronic device, and methods of fabricating a vacuum electronic device. In a non-limiting embodiment, a vacuum electronics device includes a cathode and an anode. At least one focus grid is disposed between the cathode and the anode, and the at least one focus grid is physically disconnected from the cathode. The at least one acceleration grid is disposed between the cathode and the anode, and the at least one acceleration grid is further disposed adjacent the at least one focus grid. The at least one acceleration grid is physically disconnected from the cathode.

Disclosed embodiments include vacuum electronic devices, methods of operating a vacuum electronic device, and methods of fabricating a vacuum electronic device. In a non-limiting embodiment, a vacuum electronics device includes a cathode and an anode. At least one focus grid is disposed between the cathode and the anode, and the at least one focus grid is physically disconnected from the cathode. The at least one acceleration grid is disposed between the cathode and the anode, and the at least one acceleration grid is further disposed adjacent the at least one focus grid. The at least one acceleration grid is physically disconnected from the cathode.

The embodiments provide a thermionic emission device and a method for tuning a work function in a thermionic emission device is provided. The method includes illuminating an N type semiconductor material of a first member of a thermionic emission device, wherein a work function of the N type semiconductor material is lowered by the illuminating. The method includes collecting, on one of the first member or a second member of the thermionic emission device, electrons emitted from one of the first member or the second member.

A lighting device includes a light-emitting device, a heat sink having a hollow unit inside, a translucent cover, and a thermoelectric element. The thermoelectric element includes a casing unit having a housing unit, and includes a first electrode unit, a second electrode unit having a work function different from that of the first electrode unit, and a middle unit including nanoparticles having a work function between the work function of the first electrode unit and the work function of the second electrode unit, which are provided inside the housing unit. The casing unit is provided on the inner surface of the hollow unit of the heat sink.

Embodiments relate to an apparatus for a nano-scale energy converter and an electric power generator. The apparatus includes two electrodes separated by a distance. The first electrode is manufactured to have a first work function value and the second electrode is manufactured to have a second work function value, with the first and second work function values being different. A cavity is formed by the distance between the first and second electrodes, and a nanofluid is disposed in the cavity. The nanofluid includes nanoparticles suspended in a dielectric medium. The nanoparticles have a third work function value that is greater than the first and second work function values. The relationship of the work function values of the nanoparticles to the work function values of the electrodes optimizes the transfer of electrons to the nanoparticles through Brownian motion and electron hopping.

According to one embodiment, a power generation element includes an element part. The element part includes a first conductive member, a second conductive member, and a plurality of first structure bodies provided between the first conductive member and the second conductive member. One of the first structure bodies includes a first portion and a second portion. The first portion is fixed to the first conductive member. The second portion is between the first portion and the second conductive member. A second length along a second direction of the second portion is less than a first length along the second direction of the first portion. The second direction crosses a first direction from the first conductive member toward the second conductive member.

According to one embodiment, a power generation element includes an element part. The element part includes a first conductive member, a second conductive member, and a plurality of first structure bodies provided between the first conductive member and the second conductive member. One of the first structure bodies includes a first portion and a second portion. The first portion is fixed to the first conductive member. The second portion is between the first portion and the second conductive member. A second length along a second direction of the second portion is less than a first length along the second direction of the first portion. The second direction crosses a first direction from the first conductive member toward the second conductive member.

A power generation element includes: a first housing portion including a first substrate and a first electrode portion, the first substrate including a first principal surface, and the first electrode portion being on the first principal surface; a second housing portion including a second substrate and a second electrode portion, the second substrate including a second principal surface, and the second electrode portion being on the second principal surface; and an intermediate portion including nanoparticles. The first principal surface includes a first separated surface in contact with the first electrode portion and separated from the second housing portion, and a first joint surface in contact with the second housing portion. The second principal surface includes a second separated surface in contact with the second electrode portion and separated from the first housing portion, and a second joint surface in contact with the first housing portion.