Unveiling the photoluminescence regulation of colloidal perovskite quantum dots via defect passivation and lattice distortion by potassium cations doping: Not the more the better

In this work, we have first demonstrated that the potassium cation doping effect on photoluminescence (PL) regulation of CH3NH3PbBr3 (CH3NH3+=MA+) colloidal perovskite quantum dots (QDs) is significantly different from the other alkali cation doping effects. The PL intensity will be generally enhanced with the increase doping amounts of other alkali cations. Herein, we have unveiled that the PL of the potassium-doped perovskite QDs is initially prompted by the potassium ions doping and then inhibited with further growing doping amount of the potassium ions. Furthermore, we have also demonstrated that the PL inhibition phenomenon is ascribed as quick trapping of redundant photogenerated electrons by the trap states after huge amount doping besides defect passivation and octahedral structure distortion induced by the initial doping. At the same time, the specific excited state transient absorption and the lifetime of MAxK1-xPbBr3 also confirm that the radiation recombination process is enhanced via defect passivation and lattice distortion, which is induced by moderate potassium cations doping. In addition, the PL of colloidal perovskite quantum dots can be adjusted from orange to cyan within the wavelength range of 300 nm − 600 nm and exhibit better stability.