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.

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.

Octahedral Distortions Generate a Thermally Activated Phonon-Assisted Radiative Recombination Pathway in Cubic CsPbBr Perovskite Quantum Dots.

Exciton-phonon interactions elucidate structure-function relationships that aid in the control of color purity and carrier diffusion, which is necessary for the performance-driven design of solid-state optical emitters. Temperature-dependent steady-state photoluminescence (PL) and time-resolved PL (TRPL) reveal that thermally activated exciton-phonon interactions originate from structural distortions related to vibrations in cubic CsPbBr perovskite quantum dots (PQDs) at room temperature. Exciton-phonon interactions cause performance-degrading PL line width broadening and slower electron-hole recombination.

Interplay between Perovskite Magic-Sized Clusters and Amino Lead Halide Molecular Clusters.

Recent progress has been made on the synthesis and characterization of metal halide perovskite magic-sized clusters (PMSCs) with composition ( = CHNH or Cs, = Pb, and = Cl, Br, or I). However, their mechanism of growth and structure is still not well understood. In our effort to understand their structure and growth, we discovered that a new species can be formed without the CHNH component, which we name as molecular clusters (MCs).

Low-Temperature Energy Transfer Self-Trapped Excitons in Mn-Doped 2D Organometal Halide Perovskites.

We investigate the mechanisms of energy transfer in Mn-doped ethylammonium lead bromide (EAPbBr:Mn), a two-dimensional layered perovskite (2DLP), using cryogenic optical spectroscopy. At temperature > 120 K, photoluminescence (PL) is dominated by emission from Mn, with complete suppression of band edge (BE) emission and self-trapped exciton (STE) emission. However, for < 120 K, in addition to Mn emission, PL is observed from BE and STEs.