Method for tuning work function using surface photovoltage and producing ultra-low-work-function surfaces, and devices operational therewith

A thermionic emission device, comprising:

• a device having a first member, a second member, and a gap between the first member and the second member;
• an illumination member;
• the device arranging the illumination member to illuminate or direct illumination from a source external to the second member to the first member, the first member comprising an N type semiconductor material, the illumination member providing light having energy greater than a bandgap of the N type semiconductor material to lower a work function of the N type semiconductor material;
• and
• the device arranging the second member to cooperate with the first member in thermionic emission of electrons across the gap with the N type semiconductor material of the first member so illuminated, wherein one of:
• the second member is arranged to collect electrons emitted by the first member, or the first member is arranged to collect electrons emitted by the second member.