Method of making highly-confined semiconductor nanocrystals
View Patent ↗A method of making a colloidal solution of high confinement semiconductor nanocrystals includes: forming a first solution by combining a solvent, growth ligands, and at most one semiconductor precursor; heating the first solution to the nucleation temperature; and adding to the first solution, a second solution having a solvent, growth ligands, and at least one additional and different precursor than that in the first solution to form a crude solution of nanocrystals having a compact homogenous semiconductor region. The method further includes: waiting 0.5 to 20 seconds and adding to the crude solution a third solution having a solvent, growth ligands, and at least one additional and different precursor than those in the first and second solutions; and lowering the growth temperature to enable the formation of a gradient alloy region around the compact homogenous semiconductor region, resulting in the formation of a colloidal solution of high confinement semiconductor nanocrystals.
1. A method of making a colloidal solution of high confinement semiconductor nanocrystals, comprising:
(a) forming a first solution by combining a solvent, growth ligands, and at most one semiconductor precursor;
(b) heating the first solution to a nucleation temperature;
(c) adding to the first solution, a second solution having a solvent, growth ligands, and at least one additional and different precursor that includes binary or ternary II-VI, III-V, or IV-VI semiconductor materials in the first solution to form a crude solution of nanocrystals having a compact homogenous semiconductor region;
(d) waiting for 0.5 to 20 seconds and then adding to the crude solution a third solution having a solvent, growth ligands, and at least one additional and different precursor than those in the first and second solutions and includes ternary or quaternary II-VI, III-V, or IV-VI semiconductor materials;
(e) lowering the nucleation temperature to a growth temperature to enable the formation of a gradient alloy region around the compact homogenous semiconductor region, resulting in the formation of a colloidal solution of high confinement semiconductor nanocrystals.
2. The method of claim 1 further comprising forming single or multiple shell layers on the high confinement semiconductor nanocrystals.
3. The method claim 2 wherein the shell layers are grown to a thickness of 1 to 20 monolayers.
4. The method of claim 2 wherein the shells include binary, ternary, or quaternary II-VI, III-V, or IV-VI semiconductor material, or combinations thereof.
5. The method of claim 1 wherein the nucleation temperature is between 250 to 320° C.
6. The method of claim 1 wherein in step (e) the temperature is lowered by 10 to 50° C.
7. The method of claim 1 further comprising:
(f) adding a weak acid to the crude solution containing the high confinement nanocrystals;
(g) annealing the crude solution at a temperature in a range from 180 to 260° C.; and
(h) adding ligands to the solution to prevent aggregation of the nanocrystals.
8. The method of claim 7 wherein the weak acid is acetic acid.