Quantum dot composite material, preparation method, and semiconductor device

A method for preparing a quantum dot (QD) composite material, comprising:

• synthesizing a first compound at a predetermined position;
• synthesizing a second compound on a surface of the first compound, wherein the second compound and the first compound have a same alloy composition, or have different alloy compositions;
• and
• forming the QD composite material through a cation exchange reaction between the first compound and the second compound, wherein a light-emission peak wavelength of the QD composite material experiences alternate blue-shift and red-shift,
• wherein:
• the QD composite material includes at least two QD structural units arranged sequentially along a radial direction;
• the at least two structural units include a type A1 structural unit and a type A2 structural unit, wherein the type A1 QD structural unit has a gradient alloy composition structure with an energy level width increasing along the radial direction toward a surface, and the type A2 QD structural unit has a gradient alloy composition structure with the energy level width decreasing along the radial direction toward the surface;
• and
• the two types of QD structural units are arranged alternately along the radial direction, the energy levels in adjacent QD structural units having gradient alloy composition structures are continuous.