Method for producing high-purity cesium halide, and perovskite composite material

1 . A method of producing a cesium halide, comprising following operations:

(i) preparing an aqueous Cs 2 CO 3 solution;

(ii) adding an aqueous hydrogen halide (HX) solution dropwise to the aqueous Cs 2 CO 3 solution while stirring to allow a reaction;

(iii) preparing a mixed solution by inputting and washing a reaction solution obtained in operation (ii) in a washing solvent; and

(iv) obtaining a CsX powder by filtering and drying the mixed solution of operation (iii),

wherein the cesium halide is CsX, and X is Cl, Br, or I, and

wherein the washing solvent of operation (iii) has a polarity of 4 to 6, a dipole moment of 1.60 to 4.00 debye (D), and a dielectric constant of 13 to 37.

2 . The method of claim 1 , wherein the aqueous Cs 2 CO 3 solution of operation (i) comprises 40 to 50 wt % of Cs 2 CO 3 and a remainder of water.

3 . The method of claim 1 , wherein the aqueous HX solution of operation (ii) comprises 46 to 50 wt % of HX and a remainder of water, and

wherein the dropwise addition of operation (ii) is carried out such that the aqueous Cs 2 CO 3 solution and the aqueous HX solution are mixed in a volume ratio of 1:0.87 to 1.

4 . The method of claim 1 , wherein the mixed solution of operation (iii) comprises the reaction solution and the washing solvent in a volume ratio of 1:5 or more.

5 . The method of claim 1 , wherein the CsX powder obtained in operation (iv) has a yield of 83 to 99% and a purity of 97 to 99.9%.