Abstract: Quantum dots (QDs) materials are rapidly developing in the field of electrochromic devices due to their excellent monochromatic properties and tunable luminescence. In this paper, we investigate the physical method of reducing the growth time of QDs by diluting the concentration of monomer with solvent during the growth of QDs nuclei, which can change the luminescence wavelength of QDs without changing the chemical composition ratio. Further modulation of the luminescence wavelength is achieved by growing the ZnSe and ZnSeS shell layers, resulting in green QDs with a photoluminescence wavelength of 540 nm. The principle of color change is explained by comparative experiments as well as by the LaMer model. The luminescence peak position of QDs can be controlled only by interfering with the growth phase of the nucleus. We also found that increasing the cladding temperature of the QDs shell had a positive effect on the reduction of defects in the QDs. The obtained QDs were subsequently used to prepare quantum dot electroluminescent devices, and a brightness of 348993 Cd/m² and a current efficiency of 32 Cd/A were obtained at 8 V. In addition, the method can provide new ideas for the preparation of other types of nanomaterials prepared by the thermal injection method.