A　conceptual　model　of　a　Schottky　junction　(SJ)-based　thermophotovoltaic-thermionic　device　(SJTTD)　that　can　simultaneously　convert　thermally　emitted　electrons　and　photons　into　electricity　is　proposed,　where　the　thermionic　cell　(TIC)　is　composed　of　a　tungsten-based　cathode　and　anode,　and　the　thermophotovoltaic　cell　(TPVC)　is　made　of　a　thermal　emitter　and　an　SJ.　The　thermal　emitter　simultaneously　acts　as　the　cathode　of　the　TIC　and　the　anode/p-type　silicon　interface　forms　the　SJ.　The　impacts　of　space　charge　effect　on　the　TIC　and　radiative　recombination　on　the　TPVC　are　taken　into　account.　According　to　the　theory　of　statistical　physics,　analytical　expressions　for　the　total　power　output　density　and　energy　conversion　efficiency　of　the　SJTTD　are　derived.　The　maximum　power　output　density　and　efficiency　are　calculated　numerically　by　optimizing　the　key　parameters　of　the　two　subsystems.　Further,　the　parametric　optimum　criteria　are　provided.　The　optimally　operating　states　of　the　ideal　and　non-ideal　SJTTDs　are　compared.　The　results　show　that　selecting　cathode　materials　with　high　emissivity　can　significantly　enhance　the　performance.　The　proposed　model　may　be　helpful　for　developing　high-efficiency　hybrid　electron　devices.　©　2019　IOP　Publishing　Ltd.