The Role of the Atmosphere on the Photophysics of Ligand‐Free Lead‐Halide Perovskite Nanocrystals

Abstract

Lead halide perovskite (LHP) nanocrystals (NCs) have gained attention over the past decade due to their outstanding optoelectronic properties, making them a suitable material for efficient photovoltaic and light emitting devices. Due to its soft nature, these nanostructures undergo strong structural changes upon irradiation, where these light‐induced processes are strongly influenced by the environment. Since most processing routes for LHP NCs are based on colloidal approaches, the role of factors such as stabilizing ligands or solvents is usually hard to disentangle from the interaction of external radiation with the perovskite material. Employing a recently proposed synthetic approach, where ligand‐free NCs can be grown within metal‐oxide‐based insulating nanoporous matrices, it has been feasible to perform a clean study of the effect of the surrounding atmosphere on the photophysical properties of perovskite NCs, avoiding the interference of protective capping layers or solvents. Simultaneous light‐induced photo‐activation and darkening processes are monitored and disentangled, and their relation with bulk and surface processes, respectively, demonstrated.

Responsive Optical Materials Based on Ligand-Free Perovskite Quantum Dots Embedded in Mesoporous Scaffolds

“…This behavior differs from that of organic−inorganic perovskites, in their bulk or nanocrystalline forms, for which it has been proven that a complex interplay between photoinduced defect healing, on the one hand, and degradation, on the other, gives rise to significant variations of the emitted luminescent intensity with time. 26,35 In addition, we show in Figure S6 that no change in the spectral shape was produced after 1 h irradiation.…”

“…In this context, we have demonstrated a method, compatible with standard solar cell fabrication procedures, to attain high-optical-quality (i.e., scattering-free) films embedding perovskite QDs with a variety of compositions and strict control over the nanocrystal size. , Interestingly, the host and the guest may be chosen in such a way that not all of the void space is filled with the semiconductor, allowing for the latter infiltration of other compounds. This led to the observation that scaffold-embedded QDs, as a result of the absence of ligands on their surface, are sensitive to the presence of oxygen and/or humidity in the surrounding environment, displaying a significantly different response than their bulk counterparts . Unfortunately, in the case of hybrid organic–inorganic perovskite QDs, a prolonged exposure to an intense photon flux in the presence of oxygen or water will end in the photodegradation of the nanocrystals, preventing the exploration of the potential these materials may have as responsive materials.…”

Ultrapure Green High Photoluminescence Quantum Yield from FAPbBr3 Nanocrystals Embedded in Transparent Porous Films

“…One key feature of the scaffold-supported nanocrystals is that their surface is not covered by ligands, as it happens in the case of colloidal particles. This opens the opportunity to realize clean studies of some fundamental interactions and properties, such as the electron–phonon interplay in perovskite nanocrystals, the determination of their optical constants, or their interaction with the environment, all this being possible due to the absence of surface-anchored organic ligands, always present in their colloidal counterparts. From a technological viewpoint, we could verify the successful operation of solar cells integrating insulating scaffold-supported nanocrystals, mediated by efficient dot-to-dot charge transport, as well as room temperature stabilization inside a porous structure of the highly unstable black phase of the CsPbI 3 lattice, , which in turn allowed developing optoelectronic devices based on it .…”

Conjugated Polymer–Gold–Silver Hybrid Nanoparticles for Plasmonic Energy Focusing

“…These limitations become even more dominating in the colloidal and isolated state of the plasmonic nanoparticles, since collective effects and plasmonic coupling cannot be exploited to boost their efficiency . Additionally, the dielectric ligand shells, which are typically required for the colloidal stability, sterically hinder direct surface contact and energy/carrier transfer . Nevertheless, especially colloidal systems are crucial for the above-mentioned applications like colloidal catalysis, , as building blocks for self-assembly, in biosensing, or in medicine, e.g.…”

“…4 Additionally, the dielectric ligand shells, which are typically required for the colloidal stability, sterically hinder direct surface contact and energy/ carrier transfer. 7 Nevertheless, especially colloidal systems are crucial for the above-mentioned applications like colloidal catalysis, 8,9 as building blocks for self-assembly, 10 in biosensing, 10 or in medicine, e.g. for cell-penetrating theragnostics.…”