Ultrafast Exciton Dynamics in Colloidal CsPbBr₃ Perovskite Nanocrystals: Biexciton Effect and Auger Recombination

Abstract

Exciton many-body interaction is the fundamental light−matter interaction that determines the optical response of the new class of colloidal perovskite nanocrystals of the general formula CsPbX 3 [X = Cl, Br, or I]. However, the understanding of exciton many-body interactions manifested through the transient biexcitonic Stark effect at the early time scales and the Auger recombination process in this new class of materials still remains rather incomplete. In this Article, we studied the many-body exciton interactions under controlled conditions through ultrafast transient absorption spectroscopy. A large biexcitonic redshift ∼30 meV to the effect of hot excitations on the excitonic resonance is observed at the early time scales. From the fluence-dependent studies, it is evident that the samples have only single and biexciton lifetimes, suggesting that the band edges are 2-fold degenerate. This explicit experimental evidence for the exciton many-body interactions in CsPbBr 3 nanocrystals provides a powerful tool to explore the development of their prospective applications in light-emitting devices, lasers, and solar cells.

Properties and potential optoelectronic applications of lead halide perovskite nanocrystals

“…The exciton binding energies of bulk CsPbBr 3 to be 33 and 15 meV, respectively, by the magnetooptical measurements (39). Similarly, binding energies of~30 meV were measured for large cubic CsPbBr 3 NCs (~11 nm) by using ultrafast transient absorption measurements (40). The binding energy increased to 50 meV for smaller (5.5 nm) NCs (41).…”

Colloidal Synthesis and Photophysics of M3Sb2I9 (M=Cs and Rb) Nanocrystals: Lead‐Free Perovskites

“…The origin of such an effect can be explained by considering the fact that the pump beam induced hot excitons red‐shift the transition energies of the probe excitons by Δ xx and broaden by an amount Δ ω . Then the TA at different pump‐probe delay can be written as Equation (1) where A , x i , w i and Δ w i are the amplitude, center, width and broadening of exciton transition . To obtain Δ xxi , we have globally fitted the TA at many pump‐probe delays using Equation (in which the subscripts e and g refer to the excited and ground states, respectively) which yield the value of Δ xx 1 =79±10 meV and Δ xx 2 =18±3 meV.…”

Lead‐Free Metal Halide Perovskite Nanocrystals: Challenges, Applications, and Future Aspects

“…In last one decade, material researcher already established the importance of nanoparticle in optoelectronic devices, catalysis, biology, solar to chemical energy conversion and many more. Nanocrystals of ABX 3 perovskites (especially Pb) have shown potential superior optoelectronic properties e. g. high photoluminescence quantum yield (PLQY), suppression of PL blinking, high charge carrier mobility, and long carrier diffusion length . A large number of optoelectronic devices have been prepared to utilize these NCs e. g. solar cell, light‐emitting diodes, photodetectors, and lasers .…”

“…Nanocrystals of ABX 3 perovskites (especially Pb) have shown potential superior optoelectronic properties e. g. high photoluminescence quantum yield (PLQY), suppression of PL blinking, high charge carrier mobility, and long carrier diffusion length. [29][30][31][32][33] A large number of optoelectronic devices have been prepared to utilize these NCs e. g. solar cell, lightemitting diodes, photodetectors, and lasers. [34][35][36][37][38][39][40][41] The nanodimension properties of Pb-free perovskites still yet to be explored.…”