Direct Observation of Shallow Trap States in Thermal Equilibrium with Band‐Edge Excitons in Strongly Confined CsPbBr₃ Perovskite Nanoplatelets

Abstract

low trap state density of perovskites. Confinement of the bulk 3D structure into materials of reduced dimensionalities, such as nanoplatelets (NPls) (2D), nanorods (1D) or quantum dots (0D), has also widened the range of applications to photodetection, [2-4] lasing, [5] and light

Resonant Band-Edge Emissive States in Strongly Confined CsPbBr3 Perovskite Nanoplatelets

“…Interestingly, the band-edge decay also matches the rise in the main emission at 445 nm (Supporting Information, Table S1), which may unveil the relaxation of band-edge excitons to a lower energy state. The difference between the fitting curve and the main peak signal after 1 ps arises from the fast trapping of excitons into dark states, resulting in a PL decay. − To ascertain that the rise in the main PL emission is not linked to the cooling of hot carriers, we also set the pump wavelength to 430 nm, which is close to the lowest excitonic level (Figure c). Here, the main peak rise is strictly the same as the one when pumping at higher excitation energy.…”

Probing the Exciton Diffusion Length of Short-Ligands Passivated Metal Halide Perovskite Nanocrystal Films

“…Fitting the decay curve with a biexponential function, we obtain a fast lifetime component τ fast (0.78 ns) arising from the excitons with an immediate recombination and a slow component τ slow (12.67 ns). The slow component may be a combined result of an exciton diffusion effect and an exciton trapping-detrapping mechanism at the shallow trap states. − …”

Ultrafast spectroscopy studies of carrier dynamics in semiconductor nanocrystals

“…However, the field has most recently begun to expand and apply ultrafast spectroscopy to non-Cd-based and/or more complex systems. In particular, cesium lead halide (CsPbX 3 ) and other perovskite nanocrystals have recently gained popularity for their enhanced efficiencies in quantum dot photovoltaics and high photoluminescence quantum yields and have garnered great interest in understanding their fundamental excitonic properties ( Boehme et al., 2020 ; Carroll et al., 2021 ; Dai et al., 2021 ; Qin et al., 2021 ; Socie et al., 2021 ). Doped nanocrystal systems have also sparked interest ( Dutta et al., 2018 ) as well as hybrid systems such as multilayered CdSe nanocrystals bridged with bidentate dithiocarbamate ligands ( Virgili et al., 2018 ).…”

“…•two-dimensional nanomaterials systems femtosecond single particle spectroscopy higher sensitive detection to reduce pump power needs 'all in one' box for ultrafast experiments for non-laser specialists The vast majority of the studies that have yielded fundamental understanding of the excited state in semiconductor nanocrystals have focused on CdSe-based systems, as we have detailed. However, the field has most recently begun to expand and apply ultrafast spectroscopy to non-Cd-based and/or more complex In particular, cesium lead halide (CsPbX 3 ) and other perovskite nanocrystals have recently gained popularity for their enhanced efficiencies in quantum dot photovoltaics and high photoluminescence quantum yields and have garnered great interest in understanding their fundamental excitonic properties (Boehme et al, 2020;Carroll et al, 2021;Dai et al, 2021;Qin et al, 2021;Socie et al, 2021). Doped nanocrystal systems have also sparked interest (Dutta et al, 2018) as well as hybrid systems such as multilayered CdSe nanocrystals bridged with bidentate dithiocarbamate ligands (Virgili et al, 2018).…”