Cadmium　selenide　(CdSe)-based　colloidal　quantum　dots　(QDs)　exhibit　unique　properties　such　as　tunable　colors,　narrow　emission,　high　photoluminescence　efficiency,　and　high　stability,　making　them　one　of　the　most　promising　candidates　for　next-generation　displays.　CdSe-based　QD　light-emitting　diodes　(QLEDs)　have　attracted　more　and　more　attention　mainly　due　to　their　advantages　including　high　electroluminescence　brightness,　low　turn-on　voltage,　and　ultrathin　device　structures.　However,　there　are　still　many　challenges,　mainly　including　the　lattice　defects　aroused　by　lattice　strain　during　the　QD　growth　process　and　the　surface　defects　caused　by　ligand　desorption.　CdSe-based　QLEDs　with　high　photoelectronic　performance　were　finally　achieved　in　our　work　just　by　optimizing　the　synthesis　processes　and　further　reducing　defects　in　QD　shells.　There　was　a　great　decrease　in　the　defect　density　of　the　QD　shell　indirectly　according　to　their　testing　results　in　the　fluorescence　lifetime　and　single-carrier　devices.　After　the　reaction　system　was　diluted　with　a　solvent　in　the　hot-injection　method,　there　was　some　blue　shift　in　the　QD　emission　observed　from　595　to　562　nm.　Then,　with　the　ZnSe　shell　further　coated　onto　the　QD,　the　size　of　the　effective　emission　center　was　reduced　to　some　extent,　and　further,　a　blue　shift　in　the　emission　was　obtained　with　the　wavelength　down　to　533　nm.　Finally,　on　the　outside　of　the　as-synthesized　QDs,　the　ZnS　shell　was　used　to　passivate　and　further　protect　the　ZnSe　layer,　which　greatly　increased　the　average　fluorescence　lifetime　of　the　CdSe-based　QDs　from　22.94　to　36.41　ns.　Additionally,　a　layer　of　lithium　fluoride　(LiF)　with　optimized　thickness　was　further　deposited　onto　the　QD　emitting　layer　to　prevent　ligand　desorption　from　ethanol　solvent　cleaning.　Therefore,　the　CdSe-based　QD　fluorescence　efficiency　was　greatly　improved　and　the　maximum　external　quantum　efficiency　(EQE)　of　8.06%　for　our　CdSe-based　QLEDs　was　achieved　with　a　LiF　layer　of　3　nm.　©　2024　American　Chemical　Society