Two-dimensional lead-free double perovskite and uses thereof

A process for the preparation of a double perovskite nanomaterial represented by the formula Cs2ABX6 or L4[Cs2ABX6]n-1ABX8, wherein:

• A is a metal ion selected from the group consisting of Ag(I), Au(I), and Cu(I);
• B is a metal ion selected from the group consisting of In(III), Bi(III), Sb(III), Fe(III), and Tl(III);
• X is a halogen;
• L each independently is a ligand of the formula R—COO− or R—CH2NH3+, or of the formula (R)3—P or (R)3—P═O, wherein R each independently is selected from the group consisting of (C2-C19)alkyl, (C2-C19)alkenyl, (C2-C19)alkynyl, and (C6-C14)aryl;
• and
• n is an integer of 2 to 20, representing the number of metal-halide octahedral layers present in the nanomaterial,
• wherein said nanomaterial is a two-dimensional (2D) material having a shape of a nanoplate having a diameter or lateral dimensions of about 10-50 nm, and a thickness of about 1-10 nm;
• or a nanosheet having a diameter or lateral dimensions of about 50-1500 nm, and a thickness of about 1-20 nm,
• said process comprising:
• (i) mixing a salt of metal ion A, a salt of metal ion B, and either a cesium salt or a source of said halogen, in a solvent, in the presence of an acid-base couple comprising a mixture of (a) an acid of the formula R—COOH and a base of the formula R—CH2NH2;
• or (b) an acid of the formula (R)3—P═O and a base of the formula (R)3—P;
• (ii) optionally heating the mixture obtained in (i) to a temperature of up to about 100° C.;
• and
• (iii) introducing a nucleation initiator into the reaction mixture obtained in (ii) to thereby initiate assembly of said double perovskite nanomaterial,
• provided that:
• (a) when said cesium salt is included within the salts mixed in step (i), said nucleation initiator is a benzoyl halide of the formula C6H5—C(O)—X, and the introduction of said nucleation initiator is followed by cooling of the reaction mixture, when necessary, to room temperature, to thereby obtain said 2D double perovskite nanomaterial in said solvent;
• and
• (b) when said cesium salt is not included within the salts mixed in step (ii), said nucleation initiator is a compound of the formula Cs—R, and the introduction of said nucleation initiator is preceded by cooling of the reaction mixture, when necessary, to room temperature, to thereby obtain said 2D double perovskite nanomaterial in said solvent.