Highly luminescent MAPbI(3) perovskite quantum dots with a simple purification process via ultrasound-assisted bead milling

Organic–inorganic hybrid lead halide perovskite quantum dots (QDs) have various excellent optical properties, and they have drastically enhanced the field of light-emitting diode (LED) research. However, red-emissive CH(3)NH(3) (MA) PbI(3) QDs have worse optical properties compared with those of green-emissive MAPbBr(3) QDs due to their instability under high-moisture and high-temperature conditions. Therefore, it is quite difficult to prepare MAPbI(3) QDs with good optical properties via bottom-up methods using conditions involving high temperature and high-solubility solvents. On the other hand, top-down methods for preparing MAPbI(3) QDs under an air atmosphere have attracted attention; however, there are issues, such as PL emission with a wide FWHM being obtained due to the wide particle-size distribution. In this research, red-emissive MAPbI(3) QDs were prepared via an ultrasound-assisted bead milling (UBM) method, and the MAPbI(3) QDs were purified using various carboxylate esters. As a result, we solved the issue of the wide particle-size distribution unique to top-down methods via purifying the MAPbI(3) QDs, and they achieved the following excellent optical properties: a FWHM of 44 to 48 nm and a PLQY of over 60%. Notably, a fabricated LED device with MAPbI(3) QDs purified using methyl acetate showed a PL peak at 738 nm and a FWHM of 49 nm, resulting in an excellent EQE value of 3.2%.