Reversible Color Switching in Dual-Emitting Mn(II)-Doped CsPbBr₃ Perovskite Nanorods: Dilution versus Evaporation

Abstract

Postsynthesis halide treatment can brighten perovskite nanocrystals. While this has been recently explored for undoped nanocrystals having only the exciton emission, herein, the impact of halide-enriched and -deficient environments was studied for dual-emitting Mn­(II)-doped CsPbBr3 nanorods. This was performed by adopting a self-regulated approach where the nanorod solution reversibly switched the color brightness from blue to orange and vice versa by dilution and evaporation, respectively. With control experiments, it was established that the color switching was not due to a change in the rate of the exciton energy transfer from host to dopant energy states; rather, it was related to self-regulated fulfilling and again creating halide vacancies observed with variation of nanorod concentration. Being that the halide vacancy was established as one of the key factors for controlling the brightness of these nanocrystals, this reversible switching in doped CsPbBr3 adds new fundamental insight into controlling the photoluminescence of these emerging nanocrystals.

Charge Carrier Localization in Doped Perovskite Nanocrystals Enhances Radiative Recombination

“…This finding is important for optimising colour-pure blue lightemitting diode (LED) efficiencies -a wavelength regime in which it is particularly hard to achieve high efficiencies [21][22][23][24][25]. Our results are in contrast to the emission of Mn-doped perovskite NCs reported previously [18][19][20]26], in which the excitonic emission remained mostly unchanged or decreased upon Mn doping. In those studies, the manganese doping levels are often on the order of percent [17][18][19]27,28] and in consequence the manganese emission competes with similar or even higher intensity with the excitonic emission.…”

State of the Art and Prospects for Halide Perovskite Nanocrystals

“…Pradhan and co-workers also employed a post-synthetic method to dope CsPbBr 3 NPls by mixing them with MnBr 2 in a toluene solution. They have co-related the local Mn 2+ -halide concentration with the change in emission intensity with dilution and preconcentration by evaporation of the dispersed solvent …”

“…They have co-related the local Mn 2+ -halide concentration with the change in emission intensity with dilution and preconcentration by evaporation of the dispersed solvent. 619 Although the earlier attempts to dope Mn 2+ in CsPbBr 3 NCs via one-pot hot-injection synthesis only resulted in a NC with enhanced stability but no visible Mn 2+ luminescence, 621 Parobek et al developed a direct hot-injection method that produces Mn 2+ -doped CsPbBr 3 NCs via a two-step synthesis that exhibit Mn 2+ luminescence (Figure 61). 620 In the first step of the synthesis, a Mn 2+ -doped monolayer 2D structure is synthesized (L 2 [Pb x Mn 1−x Br 4 ], where L is a ligand) as an intermediate species.…”

Self-trapped exciton emission and piezochromism in conventional 3D lead bromide perovskite nanocrystals under high pressure

“…Its excited carriers within the host perovskite excitation are trapped into Mn 2+ , leading to the formation of local electrons via energy transfer. [27][28][29][30] Doping Mn 2+ in CsPbBr 3 induces the local distortion of the octahedral framework considerably, in contrast to the case of CsPbCl 3 NCs. 31 This phenomenon occurs because of the greater disparity of M-Br (M ¼ Pb, Mn) bonddissociation energies between PbBr 2 (249 kJ mol À1 ) and MnBr 2 (314 kJ mol À1 ) compared with PbCl 2 (301 kJ mol À1 ) and MnCl 2 (338 kJ mol À1 ) precursors.…”