Research Photoluminescent Properties Of CsPbI₃ Nanocrystals Modify By Metal Ions

All-inorganic perovskite CsPbI₃ nanocrystals（NCs）are emerging as promising candidates for optoelectronic applications due to their excellent optical properties,such as appropriate energy bandgap（1.73 e V）,high color purity,narrow emission linewidth,and high photoluminescence quantum yield（PLQY）.However,CsPbI₃ is easy to transform from the cubic phase（α）to the non-luminescent perovskite phase（δ）at room temperature due to the intrinsic properties of the crystal structure with low formation energy,tolerance factor and migration activation energy,so its stability has become a huge bottleneck for practical applications.In addition,the brightness of deep red emission cannot meet the outdoor display requirements of the Rec.2020 standard international color coordinate of（0.708,0.292）.Aiming at the above problems,a metal ion-assisted modification strategy was used to obtain red emission CsPbI₃ NCs with high stability and PLQY.The research content and results of this paper mainly includes two aspects:1.A facile strategy have demonstrated using the modified hot-injection method,namely,Mg²⁺-assisted passivation of surface defects to obtain for obtain the high luminescence and stable deep-red emission（687 nm）CsPbI₃ NCs.It is found that the introduced Mg²⁺ions are mainly distributed on the surface of NCs and then passivated the NCs defects,which enhance radiative decay rate and reduce nonradiative decay rate.As a result,the as-prepared Mg²⁺-treated CsPbI₃（Mg-CsPbI₃）NCs exhibit the highest photoluminescence quantum yield（PLQY）of 95%.Moreover,the Mg-CsPbI₃ NCs colloidal solution retains 80%of its original PLQY after 80 days in atmosphere.The red perovskite light-emitting diodes based on the Mg-CsPbI₃ NCs demonstrate an external quantum efficiency of 8.4%,which shows an almost 4-fold improvement compared to the devices based on the untreated NCs.2.CsPbI₃ NCs with pure red emission were prepared by Zn²⁺ion-assisted modification at a lower synthesis temperature.The results show that introduced Zn²⁺ions are mainly successfully doped into the lattice of NCs and then passivated the NCs defects,which increase the radiative decay rate and reduce the non-radiative decay rate.The luminescence peak of as-prepared Zn²⁺-treated CsPbI₃（Zn-CsPbI₃）NCs is 635 nm,and the half-peak width is only 29.8 nm.The Zn-CsPbI₃ NCs exhibit the highest PLQY of 81%,which is 30%higher than that of the untreated NCs.Meanwhile,the results show that the structure of pure red emission Zn-CsPbI₃ NCs is the coexistence of cubic（α）and orthorhombic（γ）phases,and its morphology is uniformly distributed hexagonal crystal system.Therefore,the realization of high-efficiency and high-stability red fluorescent CsPbI₃ materials can provide an effective way to meet the requirements of wide color gamut and high-definition display in practical applications in the future.