The project aims to develop, validate and implement a novel solid-state conversion mechanism able to transform concentrated solar radiation into electric energy, at very high efficiency, with a direct conversion obtained by an enhanced electron emission from advanced semiconductor structures. Its application is in high-flux concentrating solar systems, characterized by presently mature optical technology, reduced request for active components, high cost-effectiveness.The energy conversion exploits the high radiation flux, provided by solar concentrators, by combining an efficient thermionic emission to an enhanced photo-electron emission from a cathode structure, obtained by tailoring the physical properties of advanced semiconductors able to work at temperatures as high as 1000 °C. The high operating temperatures are also connected to the possibility to exploit the residual thermal energy into electric energy by thermo-mechanical conversion.ProME3ThE2US2 will develop a proof-of-concept converter working under vacuum conditions, composed of an absorber able to employ the solar infrared (IR) radiation to provide a temperature increase, a semiconductor cathode properly deposited on it, and a work-function-matched anode, separated from the cathode by an inter-electrode spacing. The concept novelty bases on (1) use of both bandgap and over-bandgap energy to generate electrical current; (2) additional use of sub-bandgap IR radiation, with a spectral energy not able to excite photo-emitters, for augmenting the thermionic emission from cathode, (3) engineered semiconductors, able to emit electrons at lower temperatures than standard refractory metals; (4) experimentation of a hetero-structured cathode for emission enhancement by an internal field; (5) recovery of exhaust heat from the anode by thermo-mechanical conversion. It is estimated that the proposed technology could achieve a conversion efficiency of 45% if used under high-flux irradiation conditions (~1000 suns).