Large　ZnSe　quantum　dots　(QDs)　with　an　emission　peak　≈450 nm　hold　significant　promise　for　display　technologies.　However,　achieving　efficient　pure-blue　emission　through　the　enlargement　of　ZnSe　nanocrystals　remains　a　significant　challenge.　In　this　study,　a　breakthrough　is　reported　in　growing　large-size　ZnSe　QDs　well　beyond　the　exciton　Bohr　radius　through　Yb3+　doping　strategy.　Yb3+　doping　reduces　the　surface　energy　of　the　ZnSe　(220)　crystal　plane　and　alleviates　interface　strain　in　the　ZnSe/ZnS　structure,　enabling　the　QDs　to　grow　larger　while　maintaining　enhanced　crystal　stability.　The　resulting　Yb:　ZnSe/ZnS　QDs　exhibit　pure-blue　emission　at　453 nm,　with　a　full　width　at　half　maximum　(FWHM)　of　46 nm　and　a　high　photoluminescence　quantum　yield　(PLQY)　of　67.5%.　When　integrated　into　quantum　dot　light-emitting　diodes　(QLEDs),　the　devices　display　electroluminescence　(EL)　at　455 nm,　with　an　external　quantum　efficiency　(EQE)　of　1.35%,　and　a　maximum　luminance　of　1337.08 cd　m−2.　©　2025　Wiley-VCH　GmbH.