Emergence of multiple fluorophores in individual cesium lead bromide nanocrystals

Excitation wavelength-dependent quantum yield in water-soluble CdTe quantum dots

The quantum yield (QY) of semiconductor quantum dots (QDs) is severely hampered by the inherent fluorescence intermittency. The QY of QDs typically increases with an increase in the excitation wavelength. Here, we present a distinctive behavior, where the QY is found to decrease with an increase in the excitation wavelength in water-soluble CdTe QDs (CQDs). Single-particle level measurements highlight the increase in permanent single dark particles at longer wavelengths that comprehend the overall QY of the CQDs in bulk solution. Fluorescence correlation spectroscopy further revealed an increase in the number of dark particles at longer wavelengths. As confirmed by D2O/H2O exchange, the presence of H+ ions in water plays an important role in creating variable permanently dark states in the CQDs. This observation was further supported by the cell internalization study of the CQDs, where a much brighter image at a shorter wavelength than at a longer wavelength was observed. A study of the excitation wavelength-dependent QY in QDs may reveal new insights into the applicability of QDs in different device fabrication cases.

Dynamics of Photoinduced Charge Carriers in Metal-Halide Perovskites

The measurement and description of the charge-carrier lifetime (τc) is crucial for the wide-ranging applications of lead-halide perovskites. We present time-resolved microwave-detected photoconductivity decay (TRMCD) measurements and a detailed analysis of the possible recombination mechanisms including trap-assisted, radiative, and Auger recombination. We prove that performing injection-dependent measurement is crucial in identifying the recombination mechanism. We present temperature and injection level dependent measurements in CsPbBr3, which is the most common inorganic lead-halide perovskite. In this material, we observe the dominance of charge-carrier trapping, which results in ultra-long charge-carrier lifetimes. Although charge trapping can limit the effectiveness of materials in photovoltaic applications, it also offers significant advantages for various alternative uses, including delayed and persistent photodetection, charge-trap memory, afterglow light-emitting diodes, quantum information storage, and photocatalytic activity.

Unraveling the excitonics of light emission from metal-halide perovskite quantum dots

Metal halide semicondictor perovskites have been under intense investigation for their promise in light absorptive applications like photovoltaics. They have more recently experienced interest for their promise in light emissive applications. A key aspect of perovskites is their glassy, ionic lattice that exhibits dynamical disorder. One possible result of this dynamical disorder is their strong coupling between electronic and lattice degrees of freedom which may confer remarkable properties for light emission such as defect tolerance. How does the system, comprised of excitons, couple to the bath, comprised of lattice modes? How does this system-bath interaction give rise to novel light emissive properties and how do these properties give insight into the nature of these materials? We review recent work from this group in which time-resolved photoluminescence spectroscopy is used to reveal such insights. Based upon a fast time resolution of 3 ps, energy resolution, and temperature dependence, a wide variety of insights are gleaned. These insights include: lattice contributions to the emission linewidths, multiexciton formation, hot carrier cooling, excitonic fine structure, single dot superradiance, and a breakdown of the Condon approximation, all due to complex structural dynamics in these materials.

Chiral Assembly of Perovskite Nanocrystals: Sensitive Discrimination of Amino Acid Enantiomers

Chirality is a widespread phenomenon in nature and in living organisms and plays an important role in living systems. The sensitive discrimination of chiral molecular enantiomers remains a challenge in the fields of chemistry and biology. Establishing a simple, fast, and efficient strategy to discriminate the spatial configuration of chiral molecular enantiomers is of great significance. Chiral perovskite nanocrystals (PNCs) have attracted much attention because of their excellent optical activity. However, it is a challenge to prepare perovskites with both chiral and fluorescence properties for chiral sensing. In this work, we synthesized two chiral fluorescent perovskite nanocrystal assembly (PNA) enantiomers by using l- or d-phenylalanine (Phe) as chiral ligands. PNA exhibited good fluorescence recognition for l- and d-proline (Pro). Homochiral interaction led to fluorescence enhancement, while heterochiral interaction led to fluorescence quenching, and there is a good linear relationship between the fluorescence changing rate and l- or d-Pro concentration. Mechanism studies show that homochiral interaction-induced fluorescence enhancement is attributed to the disassembly of chiral PNA, while no disassembly of chiral PNA was found in heterochiral interaction-induced fluorescence quenching, which is attributed to the substitution of Phe on the surface of chiral PNA by heterochiral Pro. This work suggests that chiral perovskite can be used for chiral fluorescence sensing; it will inspire the development of chiral nanomaterials and chiral optical sensors.

Unveiling Sb3+ Doping and Tricolor Luminescence from Intrinsic Self-Trapped Excitons in Cs2ZnCl4 Crystals

Zero-dimensional (0D) lead-free halide perovskites have lately received significant interest owing to their captivating broadband emissions. An in-depth understanding of the luminescence mechanism of self-trapped excitons (STEs) and realization of effective regulation of luminescence properties have become a major challenge in the research of lead-free metal halides. Herein, we have synthesized the Cs2ZnCl4 and Sb3+-doped Cs2ZnCl4 crystals and conducted a comprehensive investigation into their distinct electronic structures and optical characteristics. The findings from both experimental and theoretical investigations indicate that the tricolor luminescence in Cs2ZnCl4 and blue emission in Sb3+-doped Cs2ZnCl4 stem from intrinsic STEs, and the near-infrared emission originates from extrinsic STEs associated with the Sb3+ ion in Sb3+-doped Cs2ZnCl4. Sb3+ doping increases the quantum yield of Cs2ZnCl4 to a large extent. In addition, intersystem crossing, exciton self-trapping, and lattice relaxation are the main reasons for the large Stokes shift. The present study is expected to provide a novel perspective for researchers in comprehending the luminescent mechanism of STEs and advancing the utilization of 0D lead-free metal halides in optoelectronic applications.

Continuous Nanomanufacturing of Inorganic Lead Halide Perovskite Nanocrystals with High-Concentration Precursors

The microscale flow preparation scheme has been widely used in the preparation of inorganic perovskite nanocrystals (NCs). It is considered to be the most promising method for large-scale production. Recently, it has been suggested that increasing the precursor concentration can further improve efficiency, but there is still a lack of understanding of high-concentration synthesis. Here, we develop a microscale flow synthesis scheme using high-concentration precursors, and the typical concentration value in the reaction phase reaches 0.035 mol/L using cesium acetate. The CsPbBr3 NCs with sharp photoluminescence (PL) at 515.7 nm can be obtained, and their PL quantum yield after post-treatment exceeds 90%. The effect of the molar ratio of Pb/Cs (Rm), reaction time, reaction temperature, and excess ligands on this flow reaction is studied. Several new phenomena are observed in our experiment. At 120 °C, some Cs4PbBr6 NCs exist in addition to the usual CsPbBr3 nanoplatelets. Excess ligands lead to the formation of numerous Cs4PbBr6 NCs with a bright green PL, and these NCs will spontaneously transform into a nonemission form in the film. Moreover, mixed-halide CsPbBrxI3-x NCs and CsPbI3 NCs are also prepared in this scheme, and then they are used to obtain LEDs in a range of colors.

Highly Emissive Zero-Dimensional Cesium Lead Iodide Perovskite Nanocrystals with Thermally Activated Delayed Photoluminescence

We utilized a modified reverse-microemulsion method to develop highly emissive and photostable zero-dimensional (0D) Cs₄Pb(Br_1-xI_x)₆ perovskite nanocrystals (PNCs). We employed single-particle photoluminescence (PL) spectroscopy to explore blinking statistics and demonstrate single-photon emission from individual PNCs. Low-temperature blinking and photon correlation studies revealed a transition from single- to multiphoton emission with progressively longer "delayed" PL components, reaching ∼70 ns at room temperature and representing a distinctive behavior to previously known iodide PNCs. Such thermally activated PL emission is explained by the existence of defect-related "reservoir" states, feeding back into the PNC's emissive state and providing multiple photons within a single excitation cycle. This work establishes a new member in the 0D class of perovskite materials, studies its photophysical properties, and reveals its potential for future optoelectronic applications.

Moisture-Dependent Blinking of Individual CsPbBr3 Nanocrystals Revealed by Single-Particle Spectroscopy

All-inorganic metal halide perovskite nanocrystals (NCs) have been exceptional candidates for high-performance solution-processed optoelectronic and photonic devices compared with organometal halide perovskite NCs due to their superior stability. However, the interactions between all-inorganic perovskite NCs and moisture, which is an acknowledged detrimental factor, are still under debate, and detailed investigations to uncover such fundamentals remain to be performed. Herein, with wide-field fluorescence microscopy, the burst photoluminescence blinking responses of CsPbBr₃ NCs were observed in ambient air, and moisture rather than oxygen was verified to be the key factor that leads to the enhanced PL intensity and reduced OFF duration. This behavior is rationalized through an effective passivation effect of the adsorbed water molecules on the surface halide vacancies on CsPbBr₃ NCs. This work validates that ∼40% humidity atmospheres are helpful for better utilizing the all-inorganic perovskites, which is evidence of their promising prospect for application.

Stable Core-Shell Structure Nanocrystals of Cs4PbBr6-Zn(moi)2 Achieved by an In Situ Surface Reconstruction Strategy for Optical Anticounterfeiting

Zero-dimensional Cs₄PbBr₆ nanocrystals (NCs) possess attractive photoluminescence (PL) properties and feature facile chemical synthesis, making them promising for application in luminescent materials. However, Cs₄PbBr₆ remains sensitive to polar solvents and thermal stimuli because of soft ionic nature of Cs₄PbBr₆ and dynamic behavior of surface ligands. Herein, a strategy controlled by an in situ surface coordination reaction is developed to fabricate stable NCs with a Cs₄PbBr₆-Zn(moi)₂ core-shell structure. It was found that the Cs₄PbBr₆ surface regulated by the use of 2-mercaptoimidazole (called moi) and the coordination between the -NH group of moi and Zn²⁺ is critical for the formation of Cs₄PbBr₆-Zn(moi)₂ core-shell NCs. Meanwhile, the thickness of the Zn(moi)₂ shell can be facilely controlled by the growth time because of the solubility of moi and Zn(OAc)₂·2H₂O in ethyl acetate. Compared to bare Cs₄PbBr₆, Cs₄PbBr₆-Zn(moi)₂ NCs exhibited highly improved polar solvent resistance and thermal stability. By combining the sensitivity of Cs₄PbBr₆ and the stability of Cs₄PbBr₆-Zn(moi)₂, we used two NCs as PL security inks to fabricate optical anticounterfeiting labels. Thus, the disposable or reusable optical anticounterfeiting label is achieved by changing the external dual-stimuli. This work provides a novel strategy to enhance the stability of Cs₄PbBr₆ and develop its potential interest for application in anticounterfeiting technologies.

Stable and Bright Electroluminescent Devices utilizing Emissive 0D Perovskite Nanocrystals Incorporated in a 3D CsPbBr3 Matrix

The 0D cesium lead halide perovskite Cs₄ PbBr₆ has drawn remarkable interest due to its highly efficient robust green emission compared to its 3D CsPbBr₃ counterpart. However, seizing the advantages of the superior photoluminescence properties for practical light-emitting devices remains elusive. To date, Cs₄ PbBr₆ has been employed only as a higher-bandgap nonluminescent matrix to passivate or provide quantum/dielectric confinement to CsPbBr₃ in light-emitting devices and to enhance its photo-/thermal/environmental stability. To resolve this disparity, a novel solvent engineering method to incorporate highly luminescent 0D Cs₄ PbBr₆ nanocrystals (perovskite nanocrystals (PNCs)) into a 3D CsPbBr₃ film, forming the active emissive layer in single-layer perovskite light-emitting electrochemical cells (PeLECs) is designed. A dramatic increase of the maximum external quantum efficiency and luminance from 2.7% and 6050 cd m^-2 for a 3D-only PeLEC to 8.3% and 11 200 cd m^-2 for a 3D-0D PNC device with only 7% by weight of 0D PNCs is observed. The majority of this increase is driven by the efficient inherent emission of the 0D PNCs, while the concomitant morphology improvement also contributes to reduced leakage current, reduced hysteresis, and enhanced operational lifetime (half-life of 129 h), making this one of the best-performing LECs reported to date.

0D Perovskites: Unique Properties, Synthesis, and Their Applications

0D perovskites have gained much attention in recent years due to their fascinating properties derived from their peculiar structure with isolated metal halide octahedra or metal halide clusters. However, the systematic discussion on the crystal and electronic structure of 0D perovskites to further understand their photophysical characteristics and the comprehensive overview of 0D perovskites for their further applications are still lacking. In this review, the unique crystal and electronic structure of 0D perovskites and their diverse properties are comprehensively analyzed, including large bandgaps, high exciton binding energy, and largely Stokes-shifted broadband emissions from self-trapped excitons. Furthermore, the photoluminescence regulation are discussed. Then, the various synthetic methods for 0D perovskite single crystals, nanocrystals, and thin films are comprehensively summarized. Finally, the emerging applications of 0D perovskites to light-emitting diodes, solar cells, detectors, and some others are illustrated, and the outlook on future research in the field is also provided.

Fast Intrinsic Emission Quenching in Cs4PbBr6 Nanocrystals

Cs4PbBr6 (0D) nanocrystals at room temperature have both been reported as nonemissive and green-emissive systems in conflicting reports, with no consensus regarding both the origin of the green emission and the emission quenching mechanism. Here, via ab initio molecular dynamics (AIMD) simulations and temperature-dependent photoluminescence (PL) spectroscopy, we show that the PL in these 0D metal halides is thermally quenched well below 300 K via strong electron-phonon coupling. To unravel the source of green emission reported for bulk 0D systems, we further study two previously suggested candidate green emitters: (i) a Br vacancy, which we demonstrate to present a strong thermal emission quenching at room temperature; (ii) an impurity, based on octahedral connectivity, that succeeds in suppressing nonradiative quenching via a reduced electron-phonon coupling in the corner-shared lead bromide octahedral network. These findings contribute to unveiling the mechanism behind the temperature-dependent PL in lead halide materials of different dimensionality.

Highly luminescent and stable quasi-2D perovskite quantum dots by introducing large organic cations

Herein, ultra-stable quasi-two-dimensional perovskite quantum dots (quasi-2D PQDs) are synthesized by introducing the butylamine cation (BA⁺) into the methylamine lead bromide perovskite (MAPbBr₃). By reducing the dimensionality of the perovskite structure, the quasi-2D perovskite (BA)₂(MA) _x-1Pb _x Br_3x+1 presents higher luminescence efficiency and better environmental stability than traditional 3D perovskites, which is mainly because the dimensionality-reduced perovskite has higher exciton binding energy and formation energy. Under an optimal MA : BA ratio of 1 : 1, the quasi-2D perovskite exhibits about four times higher luminescence efficiency (PLQY = 49.44%) than pristine MAPbBr₃; meanwhile it emits stable luminescence in an environment with 80% humidity for 50 days. Most importantly, carbon quantum dot (CQD) doping has also been applied in this work, which effectively passivates the defects of (BA)₂(MA) _x-1Pb _x Br_3x+1 via H-bond interaction, further improving the stability of the perovskite in water. Inspired by the superior performances of the proposed quasi-2D nanomaterial, a novel colorimetric method based on halide ion exchange has been developed for H₂O₂ detection, which also demonstrates that PQDs show significant potential in the field of environmental monitoring.

Revealing photoluminescence mechanisms of single CsPbBr3/Cs4PbBr6 core/shell perovskite nanocrystals

CsPbBr3 nanocrystals (NCs) encapsulated by Cs4PbBr6 has attracted extensive attention due to good stability and high photoluminescence (PL) emission efficiency. However, the origin of photoluminescence (PL) emission from CsPbBr3/Cs4PbBr6 composite materials has been controversial. In this work, we prepare CsPbBr3/Cs4PbBr6 core/shell nanoparticles and firstly study the mechanism of its photoluminescence (PL) at the single-particle level. Based on photoluminescence (PL) intensity trajectories and photon antibunching measurements, we have found that photoluminescence (PL) intensity trajectories of individual CsPbBr3/Cs4PbBr6 core/shell NCs vary from the uniform longer periods to multiple-step intensity behaviors with increasing excitation level. Meanwhile, second-order photon correlation functions exhibit single photon emission behaviors especially at lower excitation levels. However, the PL intensity trajectories of individual Cs4PbBr6 NCs demonstrate apparent "burst-like" behaviors with very high values of g 2(0) at any excitation power. Therefore, the distinguishable emission statistics help us to elucidate whether the photoluminescence (PL) emission of CsPbBr3/Cs4PbBr6 core/shell NCs stems from band-edge exciton recombination of CsPbBr3 NCs or intrinsic Br vacancy states of Cs4PbBr6 NCs. These findings provide key information about the origin of emission in CsPbBr3/Cs4PbBr6 core/shell nanoparticles, which improves their utilization in the further optoelectronic applications.

State of the Art and Prospects for Halide Perovskite Nanocrystals

Metal-halide perovskites have rapidly emerged as one of the most promising materials of the 21st century, with many exciting properties and great potential for a broad range of applications, from photovoltaics to optoelectronics and photocatalysis. The ease with which metal-halide perovskites can be synthesized in the form of brightly luminescent colloidal nanocrystals, as well as their tunable and intriguing optical and electronic properties, has attracted researchers from different disciplines of science and technology. In the last few years, there has been a significant progress in the shape-controlled synthesis of perovskite nanocrystals and understanding of their properties and applications. In this comprehensive review, researchers having expertise in different fields (chemistry, physics, and device engineering) of metal-halide perovskite nanocrystals have joined together to provide a state of the art overview and future prospects of metal-halide perovskite nanocrystal research.

Engineering the Bandgap and Surface Structure of CsPbCl3 Nanocrystals to Achieve Efficient Ultraviolet Luminescence

Herein, we report the design of novel ultraviolet luminescent CsPbCl₃ nanocrystals (NCs) with the emission peak at 381 nm through doping of cadmium ions. Subsequently, a surface passivation strategy with CdCl₂ is adopted to improve their photoluminescence quantum yield (PLQY) with the maximum value of 60.5 %, which is 67 times higher than that of the pristine counterparts. The PLQY of the surface passivated NCs remains over 50 % after one week while the pristine NCs show negligible emission. By virtue of density functional theory calculations, we reveal that the higher PLQY and better stability after surface passivation may result from the significant elimination of surface chloride vacancy (V_Cl ) defects. These findings provide fundamental insights into the optical manipulation of metal ion-doped CsPbCl₃ NCs.

High-bandwidth light inputting multilevel photoelectric memory based on thin-film transistor with a floating gate of CsPbBr3/CsPbI3 blend quantum dots

The electronic-photonic convergent systems can overcome the data transmission bottleneck for microchips by enabling processor and memory chips with high-bandwidth optical input/output. However, current silicon-based electronic-photonic systems require various functional devices/components to convert high-bandwidth optical signals into electrical ones, thus making further integrations of sophisticated systems rather difficult. Here, we demonstrate thin-film transistor-based photoelectric memories employing CsPbBr₃/CsPbI₃ blend perovskite quantum dots (PQDs) as a floating gate, and multilevel memory cells are achieved under programming and erasing modes, respectively, by imputing high-bandwidth optical signals. For different bandwidth light input (i.e. 500-550, 575-650 and 675-750 nm) with the same intensity, three levels of programming window (i.e. 3.7, 1.9 and 0.8 V) and erasing window (i.e. -1.9, -0.6 and -0.1 V) are obtained under electrical pulses, respectively. This is because the blend PQDs have two different bandgaps, and different amounts of photo-generated carriers can be produced for different wavelength optical inputs. It is noticed that the 675-750 nm light inputs have no effects on both programming and erasing windows because of no photo-carriers generation. Four memory states are demonstrated, showing enough large gaps (1.12-5.61 V) between each other, good data retention and programming/erasing endurance. By inputting different optical signals, different memory states can be switched easily. Therefore, this work directly demonstrates high-bandwidth light inputting multilevel memory cells for novel electronic-photonic systems.

Recent progress of zero-dimensional luminescent metal halides

This review provides in-depth insight into the structure–luminescence–application relationship of 0D all-inorganic/organic–inorganic hybrid metal halide luminescent materials.

Correlation of Photoluminescence and Structural Morphologies at the Individual Nanoparticle Level

Single-particle spectroscopy has demonstrated great potential for analyzing the microscopic behavior of various nanoparticles (NPs). However, high-resolution optical imaging of these materials at the nanoscale is still very challenging. Here, we present an experimental setup that combines high sensitivity of time-correlated single-photon counting (TCSPC) techniques with atomic force microscopy (AFM). This system enables single-photon detection with a time resolution of 120 ps and a spatial resolution of 5 nm. We utilize the setup to investigate the photoluminescence (PL) characteristics of both zero-dimensional (0D) and three-dimensional (3D) perovskite nanocrystals and establish a correlation between the particles’ sizes, their PL blinking, and the lifetime behavior. Our system demonstrates an unprecedented level of information, opening the door to understanding the morphology–luminescence correlation of various nanosystems.

Extent of Shallow/Deep Trap States beyond the Conduction Band Minimum in Defect-Tolerant CsPbBr3 Perovskite Quantum Dot: Control over the Degree of Charge Carrier Recombination

Perovskite quantum dots (PQDs) are known to be defect-tolerant, possessing a clean band gap with optically inactive benign defect states. However, we show that there exist significant deep trap states beyond the conduction band minimum, although the extent of shallow trap states is observed to be minimal. The extent of deep trap states beyond the conduction band minimum seems to be significant in PQDs; however, the extent is less than that of even optically robust CdSe- and InP-based core/alloy-shell QDs. In-depth analyses based on ultrafast transient absorption and ultrasensitive single-particle spectroscopic investigations decode the underlying degree of charge carrier recombination in CsPbBr₃ PQDs, which is quite important for energy applications.

A halide perovskite as a catalyst to simultaneously achieve efficient photocatalytic CO2 reduction and methanol oxidation

We have firstly demonstrated the photocatalytic utilization of a halide perovskite for combining reduction of CO₂ with selective oxidation of methanol.

Critical Roles of High- and Low-Frequency Optical Phonons in Photodynamics of Zero-Dimensional Perovskite-like (C6H22N4Cl3)SnCl3 Crystals

The zero-dimensional perovskites composed of isolated polyhedrons have unique and distinct physical properties compared with three-dimensional perovskites composed of interconnected polyhedrons. Here, we study the photodynamics of the zero-dimensional perovskite-like (C₆H₂₂N₄Cl₃)SnCl₃ single crystals composed of isolated [SnCl₃]^- tetrahedrons. They exhibit red luminescence with huge Stokes shift (2.49 eV), large spectral broadening (416 meV), and long lifetime (6.9 μs). The experiments in conjunction with the ab initio calculations reveal the special roles of high- and low-frequency phonons in the photodynamics of the (C₆H₂₂N₄Cl₃)SnCl₃ crystals. The resonance between the organic-cation-related high-frequency optical phonons and the singlet-to-triplet state transition induces strong intersystem crossing and resultant spin-forbidden luminescence. The strong electron-tetrahedron-related low-frequency optical-phonon coupling revealed by the low-temperature spectral characterization causes large spectral broadening. The strong lattice relaxation owing to localization of the electronic orbitals along with intersystem crossing accounts for the large Stokes shift.

Delayed Photoluminescence and Modified Blinking Statistics in Alumina-Encapsulated Zero-Dimensional Inorganic Perovskite Nanocrystals

We demonstrate enhancement of the photoluminescence (PL) properties of individual zero-dimensional (0D) Cs₄PbBr₆ perovskite nanocrystals (PNCs) upon encapsulation by alumina using an appropriately modified atomic layer deposition method. In addition to the increased PL intensity and improved long-term stability of encapsulated PNCs, our single-particle studies reveal substantial changes in the PL blinking statistics and the persistent appearance of the long-lived, "delayed" PL components. The blinking patterns exhibit a modification from the fast switching between fluorescent ON and OFF states found in bare PNCs to a behavior with longer ON states and more isolated OFF states in alumina-encapsulated PNCs. Controlled exposure of 0D nanocrystals to moisture suggests that the observed PL lifetime changes may be related to water-induced "reservoir" states that allow for longer-lived charge storage with subsequent back-feeding into the emissive states. Viable encapsulation of PNCs with metal oxides that can preserve and even enhance their PL properties can be utilized in the fabrication of extended structures on their basis for optoelectronic and photonic applications.

Disentangling the Luminescent Mechanism of Cs4PbBr6 Single Crystals from an Ultrafast Dynamics Perspective

New all-inorganic perovskites like Cs₄PbBr₆ provide rich luminescent tools and particularly novel physical insights, including their zero-dimensional structure and controversial emitting mechanism. The ensuing debate over the origin of the luminescence of Cs₄PbBr₆ inspired us to tackle the issue through fabricating high-quality Cs₄PbBr₆ single crystals and employing ultrafast dynamics study. Upon photoexcitation, Cs₄PbBr₆ underwent dynamics steps distinct from that of CsPbBr₃, including exciton migration to the defect level on a time scale of several hundred femtoseconds, exciton relaxation within the defect states on the picosecond time scale, and exciton recombination from the subnanosecond to nanosecond time scale. The observation disclosed that crystal defects of Cs₄PbBr₆ induced green emission while CsPbBr₃ mainly relied on quantum confinement to emit at room temperature. The study provides an in-depth understanding of the photoinduced multistep dynamics steps of Cs₄PbBr₆ associated with display and photovoltaic applications, establishing Cs₄PbBr₆ as a new candidate for uses associated with the perovskite family of materials.

Polymer spacer tunable Purcell-enhanced spontaneous emission in perovskite quantum dots coupled to plasmonic nanowire networks

Bright and fast emission of perovskite quantum dots has been demonstrated by using a polymer spacer to regulate the exciton–plasmon coupling.