In Situ Exploration of the Structural Transition during Morphology- and Efficiency-Conserving Halide Exchange on a Single Perovskite Nanocrystal.

Controlled fabrication of semiconductor nanostructures with unique physicochemical properties is vital for future technologies. In this study, transformation from red-emitting metal halide perovskite CH NH PbI nanocrystals (NCs) to green-emitting CH NH PbBr NCs was achieved without significant morphological changes and loss of photoluminescence (PL) efficiency via a controlled halide exchange reaction. In situ single-particle PL imaging along with detailed structural and elemental characterizations revealed that sudden cooperative transitions between two light-emitting states via intermediate dark states with >100 s durations during halide exchange originate from two distinct defect-mediated reconstruction processes with different activation energies (0.

Interfacial oxygen vacancies yielding long-lived holes in hematite mesocrystal-based photoanodes.

Hematite (α-FeO) is one of the most promising candidates as a photoanode materials for solar water splitting. Owing to the difficulty in suppressing the significant charge recombination, however, the photoelectrochemical (PEC) conversion efficiency of hematite is still far below the theoretical limit. Here we report thick hematite films (∼1500 nm) constructed by highly ordered and intimately attached hematite mesocrystals (MCs) for highly efficient PEC water oxidation.

Several Orders of Magnitude Difference in Charge-Transfer Kinetics Induced by Localized Trapped Charges on Mixed-Halide Perovskites.

Partial halide substitution in organolead halide perovskites MAPbX (MA = CHNH, X = Cl, Br, or I) leads to semiconductor heterostructures with precisely tuned band-gap energies, which facilitates efficient charge extraction or separation for high-performance solar cells and optoelectronic devices. In this study, partially iodide-substituted MAPbBr perovskites were prepared through a halide-exchange reaction in the liquid phase, and in situ space- and time-resolved photoluminescence profiles were acquired by means of confocal microscopy. The rates of charge transfer from the bulk MAPbBr to the surface MAPbBrI domains, which are widely distributed over a single crystal, were found to greatly depend on the excitation-power density.

Direct Observation of Charge Collection at Nanometer-Scale Iodide-Rich Perovskites during Halide Exchange Reaction on CHNHPbBr.

Organolead halide perovskites MAPbX (MA = CHNH, X = Cl, Br, or I) are known to undergo reversible halide exchange reactions, enabling bandgap tuning over the visible light region. Using single-particle photoluminescence (PL) imaging for in situ observation, we have studied the structure-dependent charge dynamics during halide exchange with iodide ions on an MAPbBr crystal. In particular, we optically detected nanometer-scale iodide-rich domains (i.