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

Lead trihalide perovskite quantum dots (PeQDs: APbX3) have greatly attracted attention as a light source for light-emitting diodes such as display due to their excellent optical properties. However, focusing on the emission wavelength of PeQDs, it was difficult to precisely control the emission wavelength by the quantum confinement effect and inserting the other X site (= halide mixture, APbX3–zX′z, 0 < z < 3). Herein, we proposed a strategy to insert the other A site with a different ionic radius in the PeQD (A1–xA′xPbX3, 0 < x < 1) to achieve precise control of the emission wavelength. Based on the energy band structure of the PeQD, it is possible to limit the factor of controlling the PeQD emission wavelength to crystal lattice shrinkage/expansion by inserting the other A site. We have successfully achieved to precisely control the emission wavelength on the PeQD in a several nanometers order by adjusting the molar ratio of two type A site cations. Precise control of the emission wavelength by only crystal lattice shrinkage/expansion of the A site mixture has been an extremely significant finding, which expands the range of applications for PeQDs.