Solar power conversion using photoelectric emission

One method of converting solar power directly into electrical power depends upon the utilization of photoelectric emission to convert the incident photons into electrical energy. This method requires that certain minimum conditions are established before power is available from the device: that is, close spacing between the photocathode and anode to minimize the effect of space charge and the electron optic barrier; a low work-function, low quantum efficiency coating upon the anode; an electron optic geometry that keeps the anode surface in the dark; and a conducting mesh or coating on the photocathode substrate to minimize the photoemissive surface resistivity. These conditions in turn require that certain problems in vacuum tube technology be solved, problems which require new Techniques and new approaches. Their solution results in a solar power converter theoretically capable of 3% conversion efficiency at a cost of $28 per watt, and specific power of 18 watts per pound. The results of the last two years of effort on this device are described and the future of the thin glass-sandwich photoemissive solar power converters are discussed.