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Metal halide perovskite (MHPs) nanocrystals (NCs) have recently emerged as promising materials for optoelectronic applications due to their exceptional photophysical properties. A comprehensive understanding of the underlying principles and key challenges associated with controlling the hot carrier (HC) cooling dynamics in MHPs is pivotal for the design of efficient perovskite‐based optoelectronic applications. This review highlights the general carrier cooling mechanism and identifies influencing crucial controlling parameters for carrier dynamics. The discussion includes strategies for manipulating HC cooling dynamics through carrier‐phonon and carrier‐carrier interactions. Notably, recent advancements in HC extraction with suitable acceptors are explored, as efficient HC extraction is imperative for the advancement of optoelectronic applications. The objective of this review is to outline potential pathways for strategically modifying carrier cooling processes to align with specific optoelectronic applications. A profound comprehension of charge carrier dynamics in MHPs NCs will pave the way for the development of highly efficient optoelectronic applications. [ABSTRACT FROM AUTHOR]

Lead halide perovskite nanocrystals (NCs) are extremely important as an absorber material for hot carrier (HC) solar cells. The extraction of the above‐bandgap excess energy of HC is essential to improve the device's performance. The fundamental understanding of the HC transfer process at the perovskite interface remains challenging. We have investigated the hot‐electron transfer dynamics at hybrid CsPbBr3/ thiol functionalized reduced graphene oxide (rGo−Ph−SH) using ultrafast transient absorption spectroscopy. Analysis reveals the significant drop in HC carrier temperature (from 1040 to 700 K) and HC cooling time (from 530 to 250 fs) in hybrid CsPbBr3/rGO−Ph−SH, suggesting the efficient hot electron transfer from CsPbBr3 NCs to surface anchored rGo−Ph−SH. We examine the HC relaxation mechanism using the electron‐longitudinal optical (LO) phonon coupling model and confirm the hot electron transfer. Here, we found that the hot‐electron transfer is three times faster than band‐edge electron transfer, with a maximum transfer efficiency of 43%. These findings shed new light on the study of the HC dynamics that could be beneficial for optoelectronic devices. [ABSTRACT FROM AUTHOR]

Metal halide perovskite nanocrystals have recently emerged as a front-runner material for high-performance solar cells. However, slowing down the hot carrier (HC) cooling of perovskites at carrier densities comparable to the sun-illumination level (≈1017 cm-3) is still a thriving challenge. A new strategy is presented to retard the HC cooling via charge localization at the CsPbBr3/PbSe heterostructure interface. Ultrafast transient absorption study reveals two times slower HC relaxation time (from 770 fs to 1.4 ps) and much higher initial HC temperature, TC (1663 K, compared to 900 K) for the heterostructure compared to the pure CsPbBr3 at 3.64 eV excitation, under 1.86 × 1017 cm-3 carrier density. Furthermore, a combination of an electron-phonon coupling model and first-principles calculations confirm the slow relaxation through the Klemens channel due to a large energy gap between the longitudinal optical (LO) and longitudinal acoustic (LA) phonon modes. The localization of charge density near the heterojunction is responsible for the up-conversion of LO modes to the higher energy and retards the HC relaxation. The findings highlight a new protocol for achieving long-lived HCs in perovskites at low carrier densities, which would benefit the future of HC photovoltaics. [ABSTRACT FROM AUTHOR]

Chiral lead halide perovskite (LHP) nanocrystals (NCs) have been attracting considerable interest for circularly polarized luminescence (CPL)-based optoelectronic applications. This study combined experimental and computational analyses to investigate how the dimensionality of 3D (cubic) to 0D (quantum dots) influences the tunable chiral emission of CsPbBr 3 LHP NCs. The circular dichroism (CD) spectra have a significant blue shift from 508 to 406 nm. The dissymmetry factors for CD ( g CD ) change from ±2.5 × 10 -3 to ±7.5 × 10 -3 as dimensionality varies from 3D to 0D in the presence of the chiral molecule (cyclohexylethylamine, CHEA). A significant luminescence dissymmetry factor ( g lum ) of ±5.6 × 10 -4 is observed in the 0D CsPbBr 3 NCs. Theoretical calculations using structural distortion parameters, the extent of charge transfer, and electrostatic potential profiles have revealed that the most significant enhancement of the chirality transfer occurs from the CHEA molecules to 0D NCs, and the order of chirality transfer from CHEA to CsPbBr 3 NCs is 0D (quantum dots) > 2D (nanoplatelet) > 3D (cubic).

Lead halide perovskite nanocrystals have received significant attention as an absorber material for designing efficient optoelectronic devices. The fundamental understanding of the hot carrier (HC) dynamics as well as its extraction in hybrid systems is essential to further boost the performance of solar cells. Herein, we have explored the electron transfer dynamics in the CsPbBr 3 -Au 144 cluster hybrid using ultrafast transient absorption spectroscopy. Our analysis reveals faster HC cooling time (from 515 to 334 fs) and a significant drop in HC temperature from 1055 to 860 K in hybrid, suggesting the hot electron transfer from CsPbBr 3 nanocrystals to the Au nanoclusters (NCs). Eventually, we observe a much faster hot electron transfer compared to the band-edge electron transfer, and 45% hot-electron transfer efficiency was achieved at 0.64 eV, above band-edge photoexcitation. Furthermore, the significant enhancement of the photocurrent to the dark current ratio in this hybrid system confirms the charge separation via the electron transfer from CsPbBr 3 nanocrystals to Au 144 NCs. These findings on HC dynamics could be beneficial for optoelectronic devices., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Manipulation of intrinsic carrier relaxation is crucial for designing efficient lead halide perovskite nanocrystal (NC) based optoelectronic devices. The influence of heterovalent Bi 3+ doping on the ultrafast carrier dynamics and hot carrier (HC) cooling relaxation of CsPbBr 3 NCs has been studied using femtosecond transient absorption spectroscopy and first-principles calculations. The initial HC temperature and LO phonon decay time point to a faster HC relaxation rate in the Bi 3+ -doped CsPbBr 3 NCs. The first-principles calculations disclose the acceleration of carrier relaxation in Bi 3+ -doped CsPbBr 3 NCs due to the appearance of localized bands (antitrap states) within the conduction band. The higher Born effective charges ( Z *) and higher soft energetic optical phonon density of states cause higher electron-phonon scattering rates in the Bi-doped CsPbBr 3 system, which is responsible for the faster HC cooling rate in doped systems.