Room-Temperature Construction of Mixed-Halide Perovskite Quantum Dots with High Photoluminescence Quantum Yield

All-inorganic cesium lead halide perovskite quantum dots (QDs) are attractive potential materials for high-performance optoelectronics because of their high photoluminescence quantum yield (PLQY), narrow emission widths, and tunable optical band gap. Hot injection is considered as a common method and is widely used for the preparation of the QDs. However, it suffers from the problems of time consumption and high cost for the mixed-halide CsPb(XY)(3) (XY is a combination of Cl and Br or Br and I) QDs because of its cumbersome preparation of precursors with different halide proportions. Here, the mixed-halide CsPb(XY)(3) QDs were synthesized by a simple and efficient way of mixing the single-halide CsPbX3 (CsPbX3; X = Cl, Br, and I) QDs stock solutions at room temperature. By modulating the ratio of stock solutions precisely, the cubic crystal structure of mixed-halide CsPb(XY)(3) QDs are obtained undergoing anion-exchange and lattice reconstruction processes. The room temperature construction of QDs showed excellent properties of bright PL with the emission peaks tunable over the entire visible light spectra, a narrow full width at half-maximum, and high PLQY, which compare favorably with the QDs prepared by the conventional hot-injection method. Furthermore, backlight light-emitting diodes (LEDs) were fabricated using the mixed-halide QDs cooperated with a commercial 365 nm PL emitting InGaN chip. The QD-assisted LEDs presented the pure and bright emission, as well as the long-term stability (3600 h) under an average relative humidity of 60%.