We synthesized cesium lead-halide perovskite colloidal nanocrystals using the hot injection method for wide-color-gamut low-cost displays. An efficient surface defect passivation technique was applied to further improve the optical performance of the green and red perovskite nanocrystals. The prepared perovskite nanocrystal solutions were formulated into inkjet printable homogeneous inks and uniformly printed on the substrate with appropriate surface control. They formed the wide-color-gamut color conversion layers of quantum dot organic light-emitting diode displays. We confirmed the excellent photophysical properties of the synthesized green/red perovskite nanocrystals and the inkjet printed color conversion layers with a photoluminescence quantum yield of 99.7%/96.2% and a wide color reproduction range of 117%.