Incorporation of rubidium cations into blue perovskite quantum dot light-emitting diodes : Via FABr-modified multi-cation hot-injection method

Solution-processed lead halide perovskite quantum dots (QDs) are emerging as one of the most promising candidates for emissive display application. Although perovskite QDs with a full spectrum of visible light emissions have been realized for years, realizing the efficient electroluminescence of blue perovskites at room temperature still faces severe challenges. Herein, we demonstrate both the efficient photoluminescence and electroluminescence of the blue perovskite QDs via a simple FABr-modified multi-cation hot-injection (FMMHI) method. The FMMHI method is unique in both the addition of FABr into the PbBr ₂ precursor solution and the incorporation of small rubidium (Rb ⁺ ) into the blue perovskite QDs light-emitting diodes (QLEDs). The addition of FABr into the precursor solution can realize strong quantum confinement effect, large exciton binding energy and high-quality perovskite QD films. Besides, the bandgap can be enlarged by the Rb ⁺ -induced perovskite octahedral distortion and strong quantum confinement effect. Excellent PLQYs of 64.5% and 49.8% were achieved for the developed greenish-blue QDs (Rb _0.33 Cs _0.67 ) _0.42 FA _0.58 PbBr ₃ and deep-blue QDs (Rb _0.33 Cs _0.67 ) _0.42 FA _0.58 PbCl _1.25 Br _1.75 in solid film state. Moreover, maximum external quantum efficiencies (EQEs) of 3.6% and 0.61% were also achieved with an electroluminescence peak wavelength at 502 and 466 nm, respectively, indicating that the perovskite QDs incorporated with Rb ⁺ possess great potential for the development of high-performance blue perovskite electroluminescence diodes.