Ultrafast exciton many-body interactions and hot-phonon bottleneck in colloidal cesium lead halide perovskite nanocrystals

Abstract

Defect tolerant perovskite nanocrystals of the general formula Cs-Pb-X3 (where X= Cl, Br and I) have shown exceptional potential in fundamental physics as well as in novel optoelectronic applications as the next generation solar cells. Although exciton many-body interactions such as biexciton Stark shift, state filling, and Auger recombination are studied extensively, other important correlated effects like bandgap renormalization (BGR) and hot phonon bottleneck are not explored in these nanocrystals. Here we experimentally demonstrate the carrier density dependence of the BGR and an effective hot phonon bottleneck in CsPb(Cl0.20Br0.80)3 mixed halide nanocrystals. The results are compared with two other halide compositions, namely, CsPbBr3 and CsPb(Br0.55I0.45)3 nanocrystals with varying bandgaps. The optical response of the nanocrystals changes dramatically across the spectral range of many hundreds of meV at high carrier density due to large BGR. We have calculated the BGR constant ≈ (6.0±0.3)×10-8 eVcm for CsPb(Cl0.20Br0.80)3 nanocrystals that provides the amount of bandgap shift as a function of carrier density. In these nanocrystals, an efficient hot phonon bottleneck is observed at a carrier density of 3.1×10 17 cm-3 that slows down the thermalization by one order of magnitude. Our findings reveal that the complex kinetic profile of the exciton dynamics can be analyzed by the global target analysis using the sequential model with increasing lifetimes.

Elucidation of Photoluminescence Blinking Mechanism and Multiexciton Dynamics in Hybrid Organic–Inorganic Perovskite Quantum Dots

“…In addition, as the dimension of PQD reaches the exciton Bohr radius (≈2 nm) of the material (PQD 1), a shoulder appears at the red side of the band‐edge state (≈490 nm) in early time as shown in 0.7 ps component spectra in Figure a. This early‐time photoinduced absorption feature is attributed to the biexciton state, in which the energy level is shifted to lower band‐edge due to the biexcitonic Stark shift . In small PQDs, increased quantum confinement effect should have resulted in stronger Coulomb interaction of biexcitons, giving rise to additional shoulder‐like feature in the early spectrum.…”

Optical studies of semiconductor perovskite nanocrystals for classical optoelectronic applications and quantum information technologies: a review

“…83,84 Under high-power laser excitation, the many excitons dwelling at the band-edge states can interact with each other through nonradiative Auger recombination, which will produce a fast decay of the exciton bleach signal within 10 to 100 ps. 82,85,86 Interestingly, it was revealed by Mondal et al 87 that the many hot excitons created in perovskite NCs by high laser powers might suffer from the phonon bottleneck effect, where their relaxation process could be significantly impeded due to the lack of available phonons for dissipating the extra thermal energy.…”

Cation Engineering in Two-Dimensional Ruddlesden–Popper Lead Iodide Perovskites with Mixed Large A-Site Cations in the Cages

“…55 The short-lived ESA feature (green, squares), is most-likely to be associated with the shot-lived hot carriers. 47,[55][56][57] The fact that the absolute intensity of the peak decreased with an increasing bandgap value (as well as the x value)…”