Colour- and structure-stable CsPbBr3-CsPb2Br5 compounded quantum dots with tuneable blue and green light emission

Even though all-inorganic lead halide perovskite (CsPbX3; X = Cl, Br, I) quantum dots (QDs) with great optoelectronic properties such as high fluorescence quantum yield, facile colour tunability, and high colour purity have been under the spotlight in recent years, their poor stability makes their application in LEDs difficult. In comparison to CsPbBr3 QDs that display green emission, CsPbCl3 QDs with blue light emission contain more defects in the material and exhibit lower fluorescence quantum yield and device service time, which is the bottleneck in realizing blue, green, and red three-base coloured perovskite QD-based LEDs. It is therefore a pressing issue to develop other techniques instead of anion exchange to adjust the light emission of CsPbX3 and simultaneously enhance the stability of the nanocrystals, especially for blue emission. In this work, CsPbBr3 QDs compounded with CsPb2Br5 (CsPbBr3-CsPb2Br5 QDs) with stable blue and green emissions are obtained using improved one-step solution-phase method. CsPb2Br5 can enhance the luminescent colour and structural stability of CsPbBr3 QDs. CsPbBr3-CsPb2Br5 QDs showed greater stability than pure CsPbBr3 QDs in various environments. Moreover, CsPbBr3-CsPb2Br5 QDs are smaller than CsPbBr3 QDs synthesized at the same temperature, which results in blue-shift of the photoluminescence spectra. Owing to the strong stability, their photoluminescence emission peak can be simply and reliably tuned continuously between 480 nm and 520 nm through the reaction temperature.