Probing the Exciton Diffusion Length of Short-Ligands Passivated Metal Halide Perovskite Nanocrystal Films

Abstract

Short-ligands passivated metal halide perovskite nanocrystal (NC) films are promising candidates for achieving high-performance optoelectronic devices such as detectors. Efficient exciton diffusion is central to this goal. Herein, we investigate the exciton diffusion length of propionic acid and butylamine passivated CsPbBr 3 NC film by quantifying the depth distribution of the excitons. This is achieved by the photoluminescence (PL) measurement of NC films with various thicknesses in transmission mode under a continuous excitation over the entire surface. Our results reveal that the exciton diffusion length of such an NC film reaches up to 2.16 ± 0.18 μm, which is enabled by the predominant multiple events of photon recycling-exciton hopping with the respective contributions of 81.1% and 18.9%. A further analysis unveils that the exciton hopping of such an NC film is beyond what dipole−dipole interaction alone can achieve, pointing to the participation of the shorter-range nonradiative energy-transfer pathways for the closely spaced NCs and even the facetsharing NCs (0 ≤ d < 1 nm). This work provides a promising avenue toward a fast exciton diffusion length evaluation based on simple PL measurements of NC films. Besides, this work also offers inspiration to potential applications involving short-ligands passivated perovskite NCs for the future.

Strongly Confined CsPbBr3 Quantum Dots as Quantum Emitters and Building Blocks for Rhombic Superlattices

“…We suggest that elucidating the precise relationship between SL strain and PL properties (here: spectrum and lifetime) may require the careful exclusion of several alternative potential origins, e.g. , size and shape segregation within the SL, self-absorption, − exciton diffusion, − and photon propagation and recycling effects. − …”

Phase modulated scanning near field optical luminescence imaging as a probe of exciton dark lifetime and diffusivity in persistently luminescent micro- and nanocrystals

“…Table 1 assesses the resolution, both spatial (lateral) and in the time domain of different techniques normally used to determine the exciton diffusion length in optical materials and nanomaterials. A significant advantage of PM-SNOL is that it possesses both significant lateral and time-domain resolution differently from state-of-the-art ultrafast [51][52][53][54][55][56][57][58][59] (Table 1, first row) imaging [60][61][62][63][64][65] (second row) techniques for exciton diffusion length measurements, which only possess either of them. As far as ultimate lateral resolution is concerned, PM-SNOL measurements are only limited by the ultimate resolution of the scanning-near field optical microscope used to perform them, which in our case is of the order of the tip aperture, 28,66 and therefore of the order of hundreds of nanometers.…”

A comprehensive review on potential of diffusion length enhancement to upraise perovskite solar cell performance

“…Exciton diffusion length can also be enhanced by working on pseudo-bilayer active layer architecture to increase crystallinity in organic SCs as shown by Jiang et al [141]. The diffusion length of short-ligand perovskite nanocrystal films in SCs also reach 2.16 ± 0.18 μm due to multiple photon-recycling (81.1%) and exciton hopping (18.9%) [143]. The significance of diffusion length optimization can be interpreted from the comparative study showing correlation between diffusion length and efficiency of perovskite SCs presented by Al-Mousoi et al [144].…”