Considerably enhanced exciton emission of CsPbCl perovskite quantum dots by the introduction of potassium and lanthanide ions.

The photoluminescence quantum yield (PLQY) of blue-violet emission of CsPbCl quantum dots (QDs) is still low, which has limited their application in multi-colour displays. It is important to search for efficient perovskite phosphors within this wavelength range. In this work, we first considerably enhanced the photoluminescence quantum yield (PLQY) of the CsPbCl QDs from 3.2 to 10.3% by the introduction of potassium ions (K). Then, various lanthanide elements (La, Y, Eu, Lu) were further doped into KCsPbCl QDs. The lanthanide doped KCsPbCl QDs still demonstrated emissions around 408 nm and the PLQY was further improved to 31%. Finally, we carried out anion exchange by gradually substituting chlorine with bromine. Efficient and tunable emissions ranging from 408-495 nm were obtained, with a maximum PLQY of 90%. This work provides a new approach to improve the efficiency of the blue-violet light of perovskite QDs.