Metastable γ-CsPbI₃ Perovskite Nanocrystals Created Using Aged Orthorhombic CsPbBr₃

Abstract

Research on anion exchange reactions (AERs) indicated that the reaction rate has a significant influence on the photoluminescence properties and crystal structures of the resulting CsPb­(Br/I)3 nanocrystals (NCs). Controllable AERs were achieved by controlling the reaction rate. Using controllable AERs, metastable γ-CsPbI3 NCs were directly obtained from the aged orthorhombic CsPbBr3 NCs. Rietveld refinement indicated that the crystal structure of parent CsPbBr3 was maintained without any phase transition or degradation. The prepared γ-CsPbI3 NCs exhibited good stability at room temperature. X-ray photoelectron spectroscopy analysis demonstrated the presence of Br and the high binding energy of Pb–Br bonding. Pb–Br bonds maintained the parent orthorhombic CsPbBr3 structure and increased the stability of γ-CsPbI3 NCs. Controllable AERs provide versatile methods to maintain the parent perovskite structure and synthesize CsPbI3 NCs with a more rigid crystal structure. They pave the way for the preparation of NCs, which are difficult to synthesize directly.

Structural Analysis and Carrier Relaxation Dynamics of 2D CsPbBr3 Nanoplatelets

“…Improvement in the value of the goodness of fit (GoF) from 1.9 to 1.6 as we go from the cubic to orthorhombic phase which also implies the presence of the orthorhombic phase. The stable orthorhombic polymorph having a similar space group ( Pnma ) was noticed earlier in the case of aged CsPbBr 3 perovskite NCs Figure S5 shows the XRD patterns of 2 and 3 ML CsPbBr 3 NPLs, exhibiting the same orthorhombic structure that is properly indexed.…”

“…The stable orthorhombic polymorph having a similar space group (Pnma) was noticed earlier in the case of aged CsPbBr 3 perovskite NCs. 53 Figure S5 shows the XRD patterns of 2 and 3 ML CsPbBr 3 NPLs, exhibiting the same orthorhombic structure that is properly indexed. The presence of lesser peaks in the XRD pattern of 3 ML NPLs than that of 2 ML NPLs suggests greater anisotropy and better orientation of (1) Å, respectively, which shows an expansion in unit cell volume from 793.12 to 824.46 Å 3 with respect to the standard powder sample.…”

NiBr2-Treated CsPbI3 Nanocrystals with Stability and Tunable Bright Luminescence for Light-Emitting Devices

“…Figure 4d shows that the peaks of Br were located at 69.07 and 67.99 eV corresponding to Br 3d 3/2 and Br 3d 5/2 orbitals. 43 The Br 3d spectrum was detected, which proves that Br − was also successfully attached to the surface of CsPbI 3 NCs. XPS analysis efficiently confirms that the improved PL was due to the synergistic effect of Br − and Ni 2+ ions.…”

“…The Ni 2p spectrum is observed in Figure c, indicating that Ni 2+ was introduced into the lattice of CsPbI 3 NCs. Figure d shows that the peaks of Br were located at 69.07 and 67.99 eV corresponding to Br 3d 3/2 and Br 3d 5/2 orbitals . The Br 3d spectrum was detected, which proves that Br – was also successfully attached to the surface of CsPbI 3 NCs.…”

Ligands Mediate Anion Exchange between Colloidal Lead-Halide Perovskite Nanocrystals

“…Halide migration and diffusion processes were investigated in perovskite nanoplates and nanowires , as well as for anion exchange between colloidal NCs and halide salts in solution. − Previous work on micrometer long nanowires established that anion exchange is facilitated by the diffusion of the halides through the lattice via a vacancy-mediated transport, leading to their homogenization . In NCs, the surface-to-volume ratio increases dramatically, accentuating surface effects.…”