The effect of Schottky barrier lowering and nonplanar emitter geometry on the performance of a thermionic energy converter

摘要

An extension of the classical model of thermionic emission was developed to include the effects of nonplanar emitter surfaces and Schottky barrier lowering (SBL) on the output of a thermionic energy converter (TEC). Nonplanar emitter geometries along with Schottky barrier lowering may be useful in increasing both the maximum output power and output current of a thermionic energy converter. The finite element method was used to calculate the enhanced normal electric field at the surface of an emitter coated with an ultra-nanocrystalline diamond (UNCD) film and patterned with field enhancing tips. The result was used to determine the local enhanced output current and power. For the geometries considered the increased surface area of the emitter plays a significant role in increasing the output power and output current. Moreover, a calculation of the single electron time of flight shows that electrons traveling through a field enhanced region of the interelectrode space might spend half as long in transit, thus helping to mitigate the negative space charge effect that degrades the performance of vacuum TECs.