Thermionic refrigerators with non-Richardson current
Most models of solid-state thermionic devices assume that all electrons withenergy in the direction of transport greater than the barrier height aretransmitted and utilize the Richardson equation. Here we consider a numberof thermionic systems where the electron energy spectrum differs from theRichardson model. The electron energy spectra for maximum refrigerationcoefficient of performance and maximum power are presented. We thenconsider multilayer solid-state nanostructures with currents not given by theRichardson equation and discuss the optimization of their energy spectrum.Nanometre gap vacuum thermionic refrigerators are also treated, wheresignificant current is provided by below the barrier tunnelling. Finally,equations are developed for devices that select electrons for emissionaccording to their total momentum, rather than simply the value in thedirection of transport as is the case with conventional devices.