Precise Control of\nthe Emission Wavelength on Perovskite\nQuantum Dots by Crystal Lattice Shrinkage/Expansion of the <i>A</i> Site Mixture

Lead trihalide perovskite quantum dots (PeQDs: <i>A</i>Pb<i>X</i><sub>3</sub>) have greatly attracted\nattention\nas a light source for light-emitting diodes such as display due to\ntheir excellent optical properties. However, focusing on the emission\nwavelength of PeQDs, it was difficult to precisely control the emission\nwavelength by the quantum confinement effect and inserting the other <i>X</i> site (= halide mixture, <i>A</i>Pb<i>X</i><sub>3–<i>z</i></sub><i>X</i><sub><i>′z</i></sub>, 0 < <i>z</i> < 3). Herein,\nwe proposed a strategy to insert the other <i>A</i> site\nwith a different ionic radius in the PeQD (<i>A</i><sub>1–<i>x</i></sub><i>A</i>′<sub><i>x</i></sub>Pb<i>X</i><sub>3,</sub> 0 < <i>x</i> < 1) to achieve precise control of the emission wavelength.\nBased on the energy band structure of the PeQD, it is possible to\nlimit the factor of controlling the PeQD emission wavelength to crystal\nlattice shrinkage/expansion by inserting the other <i>A</i> site. We have successfully achieved to precisely control the emission\nwavelength on the PeQD in a several nanometers order by adjusting\nthe molar ratio of two type <i>A</i> site cations. Precise\ncontrol of the emission wavelength by only crystal lattice shrinkage/expansion\nof the <i>A</i> site mixture has been an extremely significant\nfinding, which expands the range of applications for PeQDs.