In　this　communication,　cobaltite-based　perovskite　(CBP)　cathodes　are　directly　applied　on　the　yttria-stabilized　zirconia　(YSZ)　electrolyte　via　an　in　situ　assembly　process　without　the　addition　of　a　doped　ceria　interlayer　and　pre-sintering　at　high　temperatures.　The　results　demonstrate　for　the　first　time　that　a　CBP　electrode/YSZ　electrolyte　interface　can　be　formed　in　situ　under　cathodic　polarization　at　a　solid　oxide　fuel　cell　(SOFC)　operating　temperature　of　750　°C.　Nevertheless,　the　performance　of　cells　with　Sr-containing　CBP　cathodes　deteriorates　due　to　the　surface　segregation　of　Sr　species　and　formation　of　a　Sr-rich　reaction　layer　at　the　interface.　However,　the　stability　and　power　density　of　cells　with　in　situ　assembled　CBP　cathodes　can　be　further　enhanced　by　B-site　doping　or　by　using　a　Sr-free　CBP.　The　direct　application　of　CBPs　on　the　YSZ　electrolyte　revolutionizes　the　design　of　intermediate　temperature　SOFCs.　©　The　Royal　Society　of　Chemistry.