High brightness blue light-emitting diodes based on CsPb(Cl/Br)3 perovskite QDs with phenethylammonium chloride passivation

All inorganic perovskite quantum dots (QDs) (CsPbX3, X = Cl, Br, I) have been applied on light-emitting devices (LEDs) in recent years due to their excellent optical and optoelectronic properties. However, blue-light emitting perovskite QD LEDs (PQD-LEDs) exhibit poor performances compared with their green- and red-light emitting counterparts. Herein, we fabricated high performing blue-light emitting PQD-LEDs based on phenethylammonium chloride (PEACl) modified CsPb(Cl/Br)3 QDs. Firstly, the PEA-CsPbCl3 QDs were synthesized by introducing certain amounts of PEACl in the conventional hot-injection synthesis process. The merit of our synthesis lies in the fact that not only the Cl vacancies of CsPbCl3 QDs are efficiently modified by introducing the PEACl precursor, but also the partial long-chain organic ligands (OLA) capping on the surface of CsPbCl3 QDs are simultaneously replaced by shorter PEACl chains. Consequently, the PEA-CsPbCl3 QDs emitting at 410 nm with a PLQY of 62.3% were achieved. Furthermore, to meet the requirement of display applications, we exchanged Cl- with Br- ions at room temperature to precisely control the blue emission in the 460-470 nm spectral region and with a maximum PLQY of 80.2% at 470 nm. Finally, the PQD-LEDs based on PEA-CsPb(Cl/Br)3 perovskite QDs emitting at 462, 465, 468 and 470 nm were fabricated. The PQD-LEDs exhibit a maximal EQE of 2.15% and luminance of 620 cd m-2, which provides the highest value of luminance for the PQD-LEDs in the blue spectral range that satisfies the requirement of practical display applications.