Recently, blue emitting quantum dots (QDs) have received a great deal of attention due to light-emitting devices. QDs are considered as a material for next-generation displays based on high color reproducibility. In order to implement QLED that is completely self-luminous format, it is necessary to develop blue QDs. Many groups have implemented blue QDs based on CdSe, CdZnS, but it is not clear whether Cadmium (Cd) can be used in industry due to its toxicity. Except for Cd, few blue QDs were reported equal to 440-460nm required for display. In the current study, It has been reported that secondary phosphine are highly reactive and can produce very uniform particles. However, using secondary phosphine like Diphenylphosphine (DPP) is a limit of 420nm and more long wavelength is needed to be used on the display. We obtained an emission equivalent to 440-460nm through a SILAR method that controlled the ratio of Zinc to Selenium and small amount alloy of Tellurium. We also conducted spectral analysis according to the ratio of Tellurium. Finally, halide anion used for surface passivation to obtain highly efficient blue QDs and maximum quantum yield of 70.3%, which is the highest of the PLQY reported so far in 440-460nm.