Photon enhanced thermionic emission

Apparatus for radiant energy conversion, the apparatus comprising:

• a semiconductor photocathode having a positive electron affinity surface;
• and
• an anode separated from said photocathode;
• wherein absorption of incident radiation in said photocathode during operation of said apparatus gives rise to a distribution of electrons in a conduction band of said cathode;
• wherein some or all electrons in said distribution are thermalized with respect to a temperature of said photocathode, wherein said temperature of said photocathode is greater than 200° C. during operation of said apparatus;
• wherein some or all electrons in said distribution are emitted from said photocathode and received by said anode;
• wherein a potential difference is established between said photocathode and said anode by electrons received at said anode to provide output electrical power;
• wherein said photocathode comprises a surface coating to determine said positive electron affinity;
• wherein an electron affinity of said photocathode is between 0 eV and 1 eV, and wherein said photocathode can operate at an operating temperature greater than 200° C.