Ultrafast Spin Relaxation of Charge Carriers in Strongly Quantum Confined Methylammonium Lead Bromide Perovskite Magic-Sized Clusters.

Spin relaxation of charge carriers in strongly quantum confined perovskite magic-sized clusters has been probed, for the first time, by using polarization-controlled femtosecond transient absorption (fs-TA) spectroscopy. Fs-TA measurements with a circularly polarized pump and probe allowed for the determination of the exciton spin relaxation lifetime (∼1.5 ps) at room temperature based on the dynamics of a photoinduced absorption (PIA) feature peaked at 458 nm.

Solid-state synthesis of ligand-assisted lead halide nanoclusters.

A solid-state synthesis of blue-emitting lead halide nanoclusters has been demonstrated for the first time. The solid-state grinding synthesis provides a facile method to produce highly confined lead bromide clusters under ambient conditions. Both CHNHPbBr perovskite magic-sized clusters and lead halide molecular clusters have been produced, as confirmed by comparison to those synthesized using a ligand-assisted reprecipitation method in terms of electronic absorption, photoluminescence, and solid state characterization.

Ultrafast photoinduced charge carrier dynamics of L-cysteine and oleylamine stabilized CsPbBr3 perovskite quantum dots coupled with gold nanoparticles.

We have synthesized L-cysteine and oleylamine stabilized CsPbBr3 perovskite quantum dots (PQDs) and coupled them with gold nanoparticles (AuNPs). The PQDs and AuNPs, as well as their hybrid nanostructures (HNS), were characterized using UV-visible (UV-vis) and photoluminescence (PL) spectroscopy. The UV-vis spectra show absorption bands of the HNS at 503 and 520 nm, attributed mainly to PQDs and AuNPs, respectively.

Ultrafast Exciton Dynamics of CHNHPbBr Perovskite Nanoclusters.

Exciton dynamics of perovskite nanoclusters has been investigated for the first time using femtosecond transient absorption (TA) and time-resolved photoluminescence (TRPL) spectroscopy. The TA results show two photoinduced absorption signals at 420 and 461 nm and a photoinduced bleach (PB) signal at 448 nm. The analysis of the PB recovery kinetic decay and kinetic model uncovered multiple processes contributing to electron-hole recombination.

Effect of Lattice Disorder on Exciton Dynamics in Copper-Doped InP/ZnSeS Core/Shell Quantum Dots.

InP/ZnSeS core/shell quantum dots (QDs) with varying Cu concentrations were synthesized by a one-pot hot-injection method. X-ray diffraction and high-resolution transmission electron microscopy results indicate that Cu doping did not alter the crystal structure or particle size of the QDs. The optical shifts in UV-visible absorption and photoluminescence (PL) suggest changes in the electronic structure and induction of lattice disorder due to Cu doping.

Ultrafast Study of Excited State Dynamics of Amino Metal Halide Molecular Clusters.

The excited state dynamics of ligand-passivated PbBr molecular clusters (MCs) in solution have been investigated for the first time using femtosecond transient absorption spectroscopy. The results uncover a transient bleach (TB) feature peaked around 404 nm, matching the ground state electronic absorption band peaked at 404 nm. The TB recovery signal can be fitted with a triple exponential with fast (10 ps), medium (350 ps), and long (1.

Origin of the near 400 nm Absorption and Emission Band in the Synthesis of Cesium Lead Bromide Nanostructures: Metal Halide Molecular Clusters Rather Than Perovskite Magic-Sized Clusters.

In the synthesis of cesium lead bromide (CsPbBr) perovskite quantum dots, with an electronic absorption and emission band around 510 nm, and perovskite magic-sized clusters (PMSCs), with an electronic absorption and emission band around 430 nm, another distinct absorption and emission around 400 nm is often observed. While many would attribute this band to small perovskite particles, here we show strong evidence that this band is a result of the formation of lead bromide molecular clusters (PbBr MCs) passivated with ligands, which do not contain the A component of the ABX perovskite structure. This evidence comes from a systematic comparative study of the reaction products the A component under otherwise identical experimental conditions.