The　exhaust　heat　released　from　SOFCs　(solid　oxide　fuel　cells)　possesses　tremendous　energy　that　can　be　recovered　for　energy　cascade　utilization.　Nevertheless,　low　conversion　efficiency　or　power　density　limits　the　SOFC＇s　high-grade　waste　heat　recovery　capabilities　for　the　cogeneration　of　electric　power.　To　address　this　challenge,　a　novel　hybrid　system　coupling　a　SOFC　with　a　GTEC　(graphene-collector　thermionic　energy　converter)　is　proposed,　where　the　GTEC　harvests　the　high-grade　exhaust　heat　produced　by　the　SOFC　and　generates　extra　electricity.　It　is　found　that　the　maximum　power　density　of　the　hybrid　system　can　reach　0.774　W/cm2　at　1073　K,　which　is　1.20　times　higher　than　that　of　the　sole　SOFC,　indicating　that　the　hybrid　system　offers　a　considerable　improvement　in　output　performance.　Additionally,　the　optimal　operating　conditions　and　major　parameter　designs　of　the　hybrid　system　are　determined　from　the　perspective　of　finite　-time　thermodynamics.　Choosing　the　optimal　area　ratio,　increasing　the　SOFC　operating　temperature,　enhancing　the　heat　transfer　coefficient,　decreasing　the　thermal　emissivity,　and　fabricating　the　perfect　optical　reflector　can　further　improve　the　optimal　performance　of　the　hybrid　system.　Compared　with　other　SOFC-based　hybrid　systems,　the　SOFC-GTEC　provides　better　output　performance,　proving　that　the　GTEC　can　more　efficiently　utilize　the　exhaust　heat　produced　by　SOFC　than　other　energy　harvesting　devices.　This　work　provides　crucial　theoretical　guidance　on　the　optimal　designs　and　parametric　analysis　of　SOFC-GTEC　hybrid　systems,　thus　paving　the　way　towards　developing　high-performance　SOFC　cogeneration　systems.