Pressure-Engineered Optical and Charge Transport Properties of Mn2+/Cu2+ Codoped CsPbCl3 Perovskite Nanocrystals via Structural Progression

Theoretical and Experimental Advances in High-Pressure Behaviors of Nanoparticles

Using compressive mechanical forces, such as pressure, to induce crystallographic phase transitions and mesostructural changes while modulating material properties in nanoparticles (NPs) is a unique way to discover new phase behaviors, create novel nanostructures, and study emerging properties that are difficult to achieve under conventional conditions. In recent decades, NPs of a plethora of chemical compositions, sizes, shapes, surface ligands, and self-assembled mesostructures have been studied under pressure by in-situ scattering and/or spectroscopy techniques. As a result, the fundamental knowledge of pressure-structure-property relationships has been significantly improved, leading to a better understanding of the design guidelines for nanomaterial synthesis. In the present review, we discuss experimental progress in NP high-pressure research conducted primarily over roughly the past four years on semiconductor NPs, metal and metal oxide NPs, and perovskite NPs. We focus on the pressure-induced behaviors of NPs at both the atomic- and mesoscales, inorganic NP property changes upon compression, and the structural and property transitions of perovskite NPs under pressure. We further discuss in depth progress on molecular modeling, including simulations of ligand behavior, phase-change chalcogenides, layered transition metal dichalcogenides, boron nitride, and inorganic and hybrid organic-inorganic perovskites NPs. These models now provide both mechanistic explanations of experimental observations and predictive guidelines for future experimental design. We conclude with a summary and our insights on future directions for exploration of nanomaterial phase transition, coupling, growth, and nanoelectronic and photonic properties.

Mono- and Co-Doped Mn-Doped CsPbCl3 Perovskites with Enhanced Doping Efficiency and Photoluminescent Performance

To investigate the effect of Mn and other metal dopants on the photoelectronic performance of CsPbCl3 perovskites, we conducted a series of theoretical analyses. Our findings showed that after Mn mono-doping, the CsPbCl3 lattice contracted and the bonding strength increased, resulting in a more compact structure of the metal octahedral cage. The relaxation of the metal octahedral cage, along with the Jahn-Teller effect, results in a decrease in lattice strain between the octahedra and a reduction in the energy of the entire lattice due to the deformation of the metal octahedron. These three factors work together to reduce intrinsic defects and enhance the stability and electronic properties of CsPbCl3 perovskites. The solubility of the Mn dopant is significantly increased when co-doped with Ni, Fe, and Co dopants, as it compensates for the lattice strain induced by Mn. Doping CsPbCl3 perovskites reduces the band gap due to the decreased contributions of 3d orbitals from the dopants. Our analyses have revealed that strengthening the CsPbCl3 lattice and reducing intrinsic defects can result in improved stability and PL properties. Moreover, increasing Mn solubility and decreasing the bandgap can enhance the PLQY of orange luminescence in CsPbCl3 perovskites. These findings offer valuable insights for the development of effective strategies to enhance the photoelectronic properties of these materials.

Pressure-Induced Tunable Charge Carrier Dynamics in Mn-Doped CsPbBr3 Perovskite

All-inorganic perovskite materials (CsPbX₃) have attracted increasing attention due to their excellent photoelectric properties and stable physical and chemical properties. The dynamics of charge carriers affect the photoelectric conversion efficiencies of perovskite materials. Regulating carrier dynamics by changing pressure is interesting with respect to revealing the key microphysical processes involved. Here, ultrafast spectroscopy combined with high-pressure diamond anvil cell technology was used to study the generation and transfer of photoinduced carriers of a Mn-doped inorganic perovskite CsPbBr₃ material under pressure. Three components were obtained and assigned to thermal carrier relaxation, optical phonon-acoustic phonon scattering and Auger recombination. The time constants of the three components changed under the applied pressures. Our experimental results show that pressure can affect the crystal structure of Mn-doped CsPbBr₃ to regulate carrier dynamics. The use of metal doping not only reduces the content of toxic substances but also improves the photoelectric properties of perovskite materials. We hope that our study can provide dynamic experimental support for the exploration of new photoelectric materials.

Fluorescence-based monitoring of the pressure-induced aggregation microenvironment evolution for an AIEgen under multiple excitation channels

The development of organic solid-state luminescent materials, especially those sensitive to aggregation microenvironment, is critical for their applications in devices such as pressure-sensitive elements, sensors, and photoelectric devices. However, it still faces certain challenges and a deep understanding of the corresponding internal mechanisms is required. Here, we put forward an unconventional strategy to explore the pressure-induced evolution of the aggregation microenvironment, involving changes in molecular conformation, stacking mode, and intermolecular interaction, by monitoring the emission under multiple excitation channels based on a luminogen with aggregation-induced emission characteristics of di(p-methoxylphenyl)dibenzofulvene. Under three excitation wavelengths, the distinct emission behaviors have been interestingly observed to reveal the pressure-induced structural evolution, well consistent with the results from ultraviolet-visible absorption, high-pressure angle-dispersive X-ray diffraction, and infrared studies, which have rarely been reported before. This finding provides important insights into the design of organic solid luminescent materials and greatly promotes the development of stimulus-responsive luminescent materials.

Enhance luminescence or change morphology: effect of the doping method on Cu2+-doped CsPbBr3 perovskite nanocrystals

The effect of Cu2+ on CsPbBr3 nanocrystals is compared between the hot-injection method and postsynthetic cation-exchange reaction.

Thermal and photo stability of all inorganic lead halide perovskite nanocrystals

Inorganic lead halide perovskite (ILHP) nanocrystals (NCs) show great potential in solid state lighting and next generation display technology due to their excellent optical properties. However, almost all ILHP NCs are still facing the problem of unstable luminescence properties caused by heating and/or UV illumination. Further improving the thermal and photo stability of ILHP NCs has become the most urgent challenge for their practical application. This Perspective review specifically focuses on the thermal and photo stability of ILHP NCs, discusses and analyzes the factors that affect the thermal and photo stability of ILHP NCs from the perspective of surface ligands and structure composition, summarizes the current strategies to improve the thermal and photo stability of ILHP NCs, and presents the key challenges and perspectives on the research for the improvement of thermal and photo stability of ILHP NCs.