Abstract: A device for producing electricity. The device comprises a source of tritium radioisotopes, an element Th maintained at a temperature Th, and an element Tc maintained at a temperature Tc; Tc lower than Th. The source generates heat and is disposed in thermal communication with the element Th to maintain the temperature Th. First and second doped elements, each doped with a different dopant type, are oriented in parallel relative to the heat flow path between the element Th and the element Tc and electrically connected in series According to the Seebeck effect, a voltage is generated between the first and second doped elements due to a temperature differential between the Tc and Th, causing current to flow through the serially-connected doped elements. Helium generated during generation of the radioisotopes is vented from the device.