Synthesis, Optical Properties, and Exciton Dynamics of Organolead Bromide Perovskite Nanocrystals

Abstract

Organolead bromide CH3NH3PbBr3 perovskite nanocrystals (PNCs) with green photoluminescence (PL) have been synthesized using two different aliphatic ammonium capping ligands, octylammonium bromide (OABr) and octadecylammonium bromide (ODABr), resulting in PNC–OABr and PNC–ODABr, respectively. Structural studies by X-ray diffraction (XRD) and transmission electron microscopy (TEM) determined that the PNCs exhibit cubic phase crystal structure with average particle size dependent on capping ligand (3.9 ± 1.0 nm for PNC–OABr and 6.5 ± 1.4 nm for PNC–ODABr). The exciton dynamics of PNCs were investigated using femtosecond transient absorption (TA) techniques and singular value decomposition global fitting (SVD-GF), which revealed nonradiative recombination on the picosecond time scale mediated by surface trap states for both types of PNCs. The PL lifetime of the PNCs was measured by time-resolved photoluminescence (TRPL) spectroscopy and fit with integrated SVD-GF to determine the radiative as well as nonradiative lifetimes on the nanosecond time scale. Finally, a simple model is proposed to explain the optical and dynamic properties of the PNCs with emphasis on major exciton relaxation or electron–hole recombination processes. The results indicate that the use of capping ligand OABr resulted in PNCs with a high PL quantum yield (QY) of ∼20% (vs fluorescein, 95%), which have interesting optical properties and are promising for potential applications including photovoltaics, detectors, and light-emitting diodes (LEDs).

Colloidal lead halide perovskite nanocrystals: synthesis, optical properties and applications

“…44 Luo et al 45 used either octylammonium bromide or octadecylammonium bromide to produce perovskite NCs of 3.9 or 6.5 nm size, respectively, by means of the reprecipitation method. Although no mechanism for the size control was provided, we anticipate that the difference in size of NCs with different ligands was caused by their difference in ligand binding kinetics.…”

Unveiling the Nature of Charge Carrier Interactions by Electroabsorption Spectroscopy: An Illustration with Lead-Halide Perovskites

“…We then explain how EAS can help nanoplatelets of various thicknesses. [43][44][45][46][47] The latter are denominated 'quasi-2D' (q-2D), as they exhibit a quasi-two-dimensional structure comprising several (3-5) layers of perovskite unit cells, stabilized by a capping layer of octylammonium cations. Each of these nanostructures exhibits a unique optical signature, observable from their absorbance spectrum as shown in Fig.…”

Perovskite Quantum Dot Light-Emitting Diodes

“…Subsequently, this simple synthetic method was adopted in other groups, and an increasing number of papers have been published in this field. For example, Luo and coworkers used either octylammonium bromide or octadecylammonium bromide to produce perovskite QDs by using the reprecipitation method, with the size of QDs of 3.9 and 6.5 nm, respectively [21]. In their case, the size control of QDs was due to the different ligand-binding kinetics, and the high solubility of longer hydrophobic chain ligands could facilitate the increase of QD size.…”