All-Inorganic Colloidal Perovskite Quantum Dots: A New Class of Lasing Materials with Favorable Characteristics

Structural stability and optical properties of two-dimensional perovskite-like CsPb2Br5 microplates in response to pressure

Here, we report the structural stability and visible light response of two-dimensional (2D) layered perovskite-like CsPb2Br5 microplates (MPs) under high pressure. In situ high-pressure emission, optical absorption, and angle dispersive synchrotron X-ray diffraction indicated that CsPb2Br5 MPs experienced an isostructural phase transformation at roughly 1.6 GPa. The shrinkage of Pb-Br bond lengths and the marked change of Br-Pb-Br bond angles within the lead-bromide pentahedral motif were responsible for the pressure-induced structural modulation and the sudden band-gap change of CsPb2Br5 MPs.

Thermally stable and hydrophilic CsPbBr3/mPEG-NH2 nanocrystals with enhanced aqueous fluorescence for cell imaging

Hydrophilic CsPbBr₃/mPEG-NH₂ nanocrystals with enhanced fluorescence for cell imaging.

Luminescent perovskites: recent advances in theory and experiments

This review summarizes previous research on luminescent perovskites, including oxides and halides, with different structural dimensionality. The relationship between the crystal structure, electronic structure and properties is discussed in detail.

Direct synthesis of cubic phase CsPbI3 nanowires

One-dimensional all-inorganic halide perovskites have emerged as one of the most prominent materials in the application of optoelectronic devices due to their remarkable properties such as a low number of defects, morphological anisotropy, mechanical flexibility and fast charge transfer capability.

Lasing Supraparticles Self-Assembled from Nanocrystals

One of the most attractive commercial applications of semiconductor nanocrystals (NCs) is their use in lasers. Thanks to their high quantum yield, tunable optical properties, photostability, and wet-chemical processability, NCs have arisen as promising gain materials. Most of these applications, however, rely on incorporation of NCs in lasing cavities separately produced using sophisticated fabrication methods and often difficult to manipulate. Here, we present whispering gallery mode lasing in supraparticles (SPs) of self-assembled NCs. The SPs composed of NCs act as both lasing medium and cavity. Moreover, the synthesis of the SPs, based on an in-flow microfluidic device, allows precise control of the dimensions of the SPs, i.e. the size of the cavity, in the micrometer range with polydispersity as low as several percent. The SPs presented here show whispering gallery mode resonances with quality factors up to 320. Whispering gallery mode lasing is evidenced by a clear threshold behavior, coherent emission, and emission lifetime shortening due to the stimulation process.

CsPbBr3 Nanocrystal/MO2 (M = Si, Ti, Sn) Composites: Insight into Charge-Carrier Dynamics and Photoelectrochemical Applications

Though coating CsPbBr₃ nanocrystal (NC) with an outer layer has been regarded as an effective strategy to address its instability issues, deep investigations into the electronic interaction between CsPbBr₃ NC and coating layer have yet to be conducted. In this study, the dynamics of hot carrier and charge carrier of CsPbBr₃ nanocrystal with various MO₂ (M = Si, Ti, Sn) coating layers have been comprehensively studied. Combined transient optical characterizations (time-resolved photoluminescence and ultrafast transient absorption) and photoelectrochemical measurements reveal that coating with insulating SiO₂ accelerates the hot carrier relaxation and enhances the radiative recombination by passivating surface traps, whereas efficient charge-carrier separation and extraction are observed after coating with SnO₂ and TiO₂. The electron injection from CsPbBr₃ NC to SnO₂ (1.14 × 10⁸ s^-1) is 2-fold faster than to TiO₂ (5.4 × 10⁷ s^-1) owing to the lower conduction band edge and the higher electron mobility of SnO₂. Particularly, the first time fabricated CsPbBr₃ NC/SnO₂ composite exhibits superior stability against UV light and moisture, as well as the best photocurrent response in this study. This work has implied that rational design of the coating layer for perovskite NC can not only improve the stability but also tailor the electronic and optoelectronic properties for various applications.

Lead-Free Direct Band Gap Double-Perovskite Nanocrystals with Bright Dual-Color Emission

Lead-free double-perovskite nanocrystals (NCs), that is, Cs₂AgIn _xBi_{1- x}Cl₆ ( x = 0, 0.25, 0.5, 0.75, and 0.9), that can be tuned from indirect band gap ( x = 0, 0.25, and 0.5) to direct band gap ( x = 0.75 and 0.9) are designed. Direct band gap NCs exhibit 3 times greater absorption cross section, lower sub-band gap trap states, and >5 times photoluminescence quantum efficiency (PLQE) compared to those observed for indirect band gap NCs (Cs₂AgBiCl₆). A PLQE of 36.6% for direct band gap NCs is comparable to those observed for lead perovskite NCs in the violet region. Besides the band edge violet emission, the direct band gap NCs exhibit bright orange (570 nm) emission. Density functional theory calculations suggesting forbidden transition is responsible for the orange emission, which is supported by time-resolved PL and PL excitation spectra. The successful design of lead-free direct band gap perovskite NCs with superior optical properties opens the door for high-performance lead-free perovskite optoelectronic devices.

One-Step Co-Evaporation of All-Inorganic Perovskite Thin Films with Room-Temperature Ultralow Amplified Spontaneous Emission Threshold and Air Stability

Inorganic cesium lead halide perovskite has been successfully applied in the optoelectronic field due to its remarkable optical gain properties. Unfortunately, conventional solution-processed CsPbX₃ films suffer unavoidable pinhole defects and poor surface morphology, severely limiting their performance on amplified spontaneous emission (ASE) and lasing applications. Herein, a dual-source thermal evaporation approach is explored to achieve a uniform and high-coverage CsPbX₃ polycrystalline thin film. It was found that one-step co-evaporated CsPbBr₃ (OC-CsPbBr₃) thin films without post-annealing exhibit an ultralow ASE threshold of ∼3.3 μJ/cm² and a gain coefficient above 300 cm^-1. The coexistence of cubic and orthorhombic phases in these materials naturally form an energy cascade for the exciton transfer process, which enables rapid accumulation of excitons. Stable ASE intensity without degradation for at least 7 h is also realized from OC-CsPbBr₃ thin films under continuous excitation, which is superior to that in the solution-processed CsPbBr₃ thin films. Notably, a Fabry-Pérot cavity laser based on the OC-CsPbBr₃ thin film is first achieved, featuring an ultralow lasing threshold (1.7 μJ/cm²) and directional output (a beam divergence of ∼3.8°). This work highlights the noteworthy optical properties of OC-CsPbBr₃ thin films, leading to potential available applications in integrated optoelectronic chips.

Low Power Consumption Red Light-Emitting Diodes Based on Inorganic Perovskite Quantum Dots under an Alternating Current Driving Mode

Inorganic perovskites have emerged as a promising candidate for light-emitting devices due to their high stability and tunable band gap. However, the power consumption and brightness have always been an issue for perovskite light-emitting diodes (PeLEDs). Here, we improved the luminescence intensity and decreased the current density of the PeLEDs based on CsPbI₃ quantum dots (QDs) and p-type Si substrate through an alternating current (AC) driving mode. For the different driving voltage modes (under a sine pulsed bias or square pulsed bias), a frequency-dependent electroluminescent (EL) behavior was observed. The devices under a square pulsed bias present a stronger EL intensity under the same voltage due to less thermal degradation at the interface. The red PeLEDs under a square pulsed bias driving demonstrate that the EL intensity drop-off phenomenon was further improved, and the integrated EL intensity shows the almost linear increase with the increasing driving voltage above 8.5 V. Additionally, compared to the direct current (DC) driving mode, the red PeLEDs under the AC condition exhibit higher operating stability, which is mainly due to the reducing accumulated charges in the devices. Our work provides an effective approach for obtaining strong brightness, low power consumption, and high stability light-emitting devices, which will exert a profound influence on coupling LEDs with household power supplies directly.

Fast Room-Temperature Cation Exchange Synthesis of Mn-Doped CsPbCl3 Nanocrystals Driven by Dynamic Halogen Exchange

Currently, it is of great challenge to achieve cation exchange in CsPbX₃ (X = Cl, Br, I) perovskite nanocrystals (NCs) on account of rigid Pb²⁺ octahedral coordination protected by six halogen anions (PbX₆^4-). Herein, we demonstrate that dynamic halogen exchange can effectively open up PbX₆^4- octahedrons and enable fast Mn-to-Pb cation exchange at room temperature in a few seconds. Importantly, Cl concentration rather than Mn one is demonstrated to be a dominant factor for cation exchange, where different Mn²⁺/Cl^- salts can be adopted as Mn/Cl sources and Cl-to-Cl or Cl-to-Br anion exchange is the necessary prerequisite. Such a facile synthesizing method can lead to the feasibility of tuning emissive colors for the Mn-doped CsPb(Cl/Br)₃ NCs by controlling both cation and anion exchanges and open a new way to replace Pb²⁺ in CsPbX₃ NCs by other nontoxic metal elements.

Anion exchange in inorganic perovskite nanocrystal polymer composites

We demonstrate a facile, low-cost and room-temperature method of anion exchange in cesium lead bromide nanocrystals (CsPbBr3 NCs), embedded into a polymer matrix. The anion exchange occurs upon exposure of the solid CsPbBr3 NCs/PDMS nanocomposite to a controlled anion precursor gas atmosphere. The rate and extent of the anion exchange reaction can be controlled via the variation of either the exposure time or the relative concentration of the anion precursor gas. Post-synthesis chemical transformation of perovskite nanocrystal-polymer composites is not readily achievable using conventional methods of anion exchange, which renders the gas-assisted strategy extremely useful. We envisage that this work will enable the development of solid-state perovskite NC optoelectronic devices.

Novel Fluorescence Sensor Based on All-Inorganic Perovskite Quantum Dots Coated with Molecularly Imprinted Polymers for Highly Selective and Sensitive Detection of Omethoate

All-inorganic cesium lead halide perovskites (CsPbX₃, X = Cl, Br, and I) have attracted considerable attention with superior electrical and photophysical properties. In this study, luminescent perovskite (CsPbBr₃) quantum dots (QDs) as sensing elements combined with molecularly imprinted polymers (MIPs) are used for the detection of omethoate (OMT). The new MIPs@CsPbBr₃ QDs were synthesized successfully through the imprinting technology with a sol-gel reaction. The fluorescence (FL) of the MIPs@CsPbBr₃ QDs was quenched obviously on loading the MIPs with OMT, the linear range of OMT was from 50 to 400 ng/mL, and the detection limit was 18.8 ng/mL. The imprinting factor was 3.2, which indicated excellent specificity of the MIPs for the inorganic metal halide (IMH) perovskites. The novel composite possesses the outstanding FL capability of CsPbBr₃ QDs and the high selectivity of molecular imprinting technology, which can convert the specific interactions between template and the imprinted cavities to apparent changes in the FL intensity. Hence, a selective and simple FL sensor for direct and fast detection of organophosphorus pesticide in vegetable and soil samples was developed here. The present work also illustrates the potential of IMH perovskites for sensor applications in biological and environmental detection.

Impurity Ions Codoped Cesium Lead Halide Perovskite Nanocrystals with Bright White Light Emission toward Ultraviolet-White Light-Emitting Diode

White light-emitting diodes (WLEDs) based on all-inorganic perovskite CsPbX₃ (X = Cl, Br, I) nanocrystals (NCs) have attracted extensive interests. However, the native ion exchange among halides makes them extremely difficult to realize the white emission. Herein, we demonstrate a novel strategy to obtain WLED phosphors based on the codoping of different metal ion pairs, such as Ce³⁺/Mn²⁺, Ce³⁺/Eu³⁺, Ce³⁺/Sm³⁺, Bi³⁺/Eu³⁺, and Bi³⁺/Sm³⁺ into stable CsPbCl₃ and CsPbCl _xBr_{3- x} NCs. Notably, by the typical anion exchange reaction, the highly efficient white emission of Ce³⁺/Mn²⁺-codoped all-inorganic CsPbCl_1.8Br_1.2 perovskite NCs was achieved, with an optimal photoluminescence quantum yield of 75%, which is much higher than the present record of 49% for single perovskite phosphors. Moreover, the WLED with a luminous efficiency of 51 lm/W based on the 365 nm ultraviolet chip and CsPbCl_1.8Br_1.2:Ce³⁺/Mn²⁺ nanophosphor was achieved. This work represents a novel device for perovskite-based phosphor-converted WLEDs.

Water-Borne Perovskite Quantum Dot-Loaded, Polystyrene Latex Ink

Highly lipophilic nanocrystals (NCs) of cesium lead halides were successfully embedded in polystyrene (PS) particles by deliberately controlling the swelling of the PS particles in the mixtures of good and bad organic solvents. The resulting composite particles were readily transferred into water via simple stepwise solvent exchange, which yielded water-borne perovskite NC-based inks with outstanding structural and chemical stability in aqueous media. Minimal change in the photoluminescence (PL) of the NCs loaded in the PS particles was visible after 1 month of incubation of the composite particles in water in a broad pH range from 1 to 14, which could otherwise be hardly realized. Loading into the PS particles also made the NCs highly stable against polar organic solvents, such as ethanol, intense light irradiation, and heat. The NC PL intensity slightly changed after the composite particles were heated at 75°C and under irradiation of strong blue light (@365 nm) for 1 h. Furthermore, the PS matrices could effectively inhibit the exchange of halide anions between two differently sized perovskite NCs loaded therein, thereby offering a considerable technical advantage in the application of multiple perovskite NCs for multicolor display in the future.

CsBr-Induced Stable CsPbI3- xBr x ( x < 1) Perovskite Films at Low Temperature for Highly Efficient Planar Heterojunction Solar Cells

All-inorganic cesium lead perovskites have emerged as alternative absorbing layers in solar cells owing to their superb thermal stability compared with the organic-inorganic hybrid perovskites. However, the desired cubic CsPbI₃ phase forms at a high temperature and suffers from a phase transition to the orthorhombic yellow phase at room temperature. A developed nonstoichiometric method is applied to fabricate CsPbI_{3- x}Br _x ( x < 1) films by adding excess CsBr into the precursor solution. The excess CsBr in the precursor solution helps to produce a microstrain in the lattice to stabilize the cubic CsPbI₃ phase at low temperature and incorporate a small part of Br^- into the CsPbI₃ lattice. At the optimal CsBr concentration (0.5 M), the corresponding solar cell achieves a power conversion efficiency of 10.92%. This work provides an effective way to stabilize the cubic CsPbI_{3- x}Br _x ( x < 1) phase at low temperature to further improve the performance of all-inorganic perovskite solar cells.

Novel properties and applications of carbon nanodots

In the most recent decade, carbon dots have drawn intensive attention and triggered substantial investigation. Carbon dots manifest superior merits, including excellent biocompatibility both in vitro and in vivo, resistance to photobleaching, easy surface functionalization and bio-conjugation, outstanding colloidal stability, eco-friendly synthesis, and low cost. All of these endow them with the great potential to replace conventional unsatisfactory fluorescent heavy metal-containing semiconductor quantum dots or organic dyes. Even though the understanding of their photoluminescence mechanism is still controversial, carbon dots have already exhibited many versatile applications. In this article, we summarize and review the recent progress achieved in the field of carbon dots, and provide a comprehensive summary and discussion on their synthesis methods and emission mechanisms. We also present the applications of carbon dots in bioimaging, drug delivery, microfluidics, light emitting diode (LED), sensing, logic gates, and chiral photonics, etc. Some unaddressed issues, challenges, and future prospects of carbon dots are also discussed. We envision that carbon dots will eventually have great commercial utilization and will become a strong competitor to some currently used fluorescent materials. It is our hope that this review will provide insights into both the fundamental research and practical applications of carbon dots.

All-Inorganic Perovskite Nanocrystals with a Stellar Set of Stabilities and Their Use in White Light-Emitting Diodes

We report a simple, robust, and inexpensive strategy to enable all-inorganic CsPbX₃ perovskite nanocrystals (NCs) with a set of markedly improved stabilities, that is, water stability, compositional stability, phase stability, and phase segregation stability via impregnating them in solid organic salt matrices (i.e., metal stearate; MSt). In addition to acting as matrices, MSt also functions as the ligand bound to the surface of CsPbX₃ NCs, thereby eliminating the potential damage of NCs commonly encountered during purification as in copious past work. Quite intriguingly, the resulting CsPbX₃-MSt nanocomposites display an outstanding suite of stabilities. First, they retain high emission in the presence of water because of the insolubility of MSt in water, signifying their excellent water stability. Second, anion exchange between CsPbBr₃-MSt and CsPbI₃-MSt nanocomposites is greatly suppressed. This can be ascribed to the efficient coating of MSt, thus effectively isolating the contact between CsPbBr₃ and CsPbI₃ NCs, reflecting notable compositional stability. Third, remarkably, after being impregnated by MSt, the resulting CsPbI₃-MSt nanocomposites sustain the cubic phase of CsPbI₃ and high emission, manifesting the strikingly improved phase stability. Finally, phase segregation of CsPbBr_1.5I_1.5 NCs is arrested via the MSt encapsulation (i.e., no formation of the respective CsPbBr₃ and CsPbI₃), thus rendering pure and stable photoluminescence (i.e., demonstration of phase segregation stability). Notably, when assembled into typical white light-emitting diode architecture, CsPbBr_1.5I_1.5-MSt nanocomposites exhibit appealing performance, including a high color rendering index ( R_a) and a low color temperature ( T_c). As such, the judicious encapsulation of perovskite NCs into organic salts represents a facile and robust strategy for creating high-quality solid-state luminophores for use in optoelectronic devices.

Lattice Dynamics and Thermal Stability of Cubic-Phase CsPbI3 Quantum Dots

Cubic-phase CsPbI₃ quantum dots (QDs) have been recently synthesized with merits of excellent optoelectronic performance. However, vital properties of cubic CsPbI₃ including lattice dynamics and stability at high temperature remain poorly explored. We fabricate cubic CsPbI₃ QDs and study their lattice dynamic and thermal stability to 700 K. We obtain Raman modes of cubic CsPbI₃ QDs from 300 to 500 K at ultra-low-frequency range down to 15 cm^-1, consistent with first-principles calculations. Above 550 K, the modification of Raman features suggests sample degradation. Consistently, temperature-dependent photoluminescence measurements indicate the absence of other luminescence phases up to 700 K. With increasing temperature, the CsPbI₃ QD photoluminescence peak has a blue shift with exponentially decreasing intensity, showing faster electronic degradation than structural degradation. Our work provides detailed investigation of CsPbI₃ QD lattice dynamics, band gap, and their high-temperature behavior, potentially useful for their emerging optoelectronic applications.

Recombination Dynamics Study on Nanostructured Perovskite Light-Emitting Devices

The field of organic-inorganic hybrid perovskite light-emitting diodes (PeLEDs) has developed rapidly in recent years. Although the performance of PeLEDs continues to improve through film quality control and device optimization, little research has been dedicated to understanding the recombination dynamics in perovskite thin films. Likewise, little has been done to investigate the effects of recombination dynamics on the overall light-emitting behavior of PeLEDs. Therefore, this study investigates the recombination dynamics of CH₃ NH₃ PbI₃ thin films with differing crystal sizes by measurement of fluence-dependent transient absorption dynamics and time-resolved photoluminescence. The aim is to find out the link between recombination dynamics and device behavior in PeLEDs. It is found that bimolecular and Auger recombination become more efficient as the crystal size decreases and monomolecular recombination rate is affected by the trap density of perovskite. By defining the radiative efficiency Φ(n), which relates to the monomolecular, bimolecular, and Auger recombination, the fundamental recombination properties of CH₃ NH₃ PbI₃ films are discerned in quantitative terms. These findings help us to understand the light emission behavior of PeLEDs. This study takes an important step toward establishing the relationship between film structure, recombination dynamics, and device behavior for PeLEDs, thereby providing useful insights toward the design of better perovskite devices.

Yb3+ and Yb3+/Er3+ Doping for Near-Infrared Emission and Improved Stability of CsPbCl3 Nanocrystals

Lead halide perovskite nanocrystals (NCs) exhibit excellent tunable emissions covering the entire visible spectral region, but they do not emit near-infrared (NIR) light. We synthesized rare earth element doped CsPbCl3 NCs for NIR emission. The Yb3+ doped CsPbCl3 NCs emitted strong 986 nm NIR light; the Yb3+/Er3+ co-doped CsPbCl3 NCs emitted at 1533 nm. The total photoluminescence quantum yield (PL QY) of the CsPbCl3 NCs changed from 5.0% to 127.8% upon incorporating 2.0% Yb3+, a factor of 25.6 times enhancement. The material's stability was tested under continuous ultraviolet (365 nm) irradiation. The doped CsPbCl3 NCs exhibited a better stability than the undoped one. The PL intensity of the undoped CsPbCl3 NCs dropped to 20% of the initial value in 27 h, while the doped one took 85 h.

Near-infrared-triggered photon upconversion tuning in all-inorganic cesium lead halide perovskite quantum dots

All-inorganic CsPbX₃ (X = Cl, Br, and I) perovskite quantum dots (PeQDs) have shown great promise in optoelectronics and photovoltaics owing to their outstanding linear optical properties; however, nonlinear upconversion is limited by the small cross-section of multiphoton absorption, necessitating high power density excitation. Herein, we report a convenient and versatile strategy to fine tuning the upconversion luminescence in CsPbX₃ PeQDs through sensitization by lanthanide-doped nanoparticles. Full-color emission with wavelengths beyond the availability of lanthanides is achieved through tailoring of the PeQDs bandgap, in parallel with the inherent high conversion efficiency of energy transfer upconversion under low power density excitation. Importantly, the luminescent lifetimes of the excitons can be enormously lengthened from the intrinsic nanosecond scale to milliseconds depending on the lifetimes of lanthanide ions. These findings provide a general approach to stimulate photon upconversion in PeQDs, thereby opening up a new avenue for exploring novel and versatile applications of PeQDs.

In situ synthesis and macroscale alignment of CsPbBr3 perovskite nanorods in a polymer matrix

We report an in situ catalyst-free strategy to synthesize inorganic CsPbBr3 perovskite nanorods in a polymer matrix (NRs-PM) with good dimensional control, outstanding optical properties and ultrahigh environmental stability. Polarization photoluminescence (PL) imaging with high spatial resolution was carried out for the first time on single nanorod (NR) and shows a relatively high local polarization ratio (∼0.4) consistent with theoretical predictions based on a dielectric contrast model. We further demonstrate that macroscale alignment of the CsPbBr3 nanorods can be achieved through mechanically stretching the NRs-PM films at elevated temperature, without deteriorating the optical quality of the NRs. A polarization ratio of 0.23 is observed for these aligned NRs-PM films, suggesting their potential as polarized down-converters to increase the light efficiency in liquid crystal display (LCD) backlights.

All-Solution-Processed Perovskite Quantum Dots Light-Emitting Diodes Based on the Solvent Engineering Strategy

Perovskite quantum dots (PeQDs) have emerged as a new kind of nanomaterial in various applications, especially light-emitting diodes (LEDs). However, the synthesis of PeQDs is relatively complicated and the electron transport layer (ETL) is usually fabricated in a vacuum because of the dissolution of PeQDs films in organic solvents, which will increase the difficulty and cost in mass production. Here, a simple one-step "ultrasonic bath" treatment to synthesis PeQDs is adopted and applied into the PeQDs-LEDs. Meanwhile, an all-solution process is developed to fabricate PeQDs-LEDs based on the solvent engineering strategy. By using methyl acetate (MeOAc) as the solvent of ETL, the all-solution-processed PeQDs-LEDs exhibit bright luminance with the maximum current efficiency of 3.26 cd/A. This work is simple and easy to be scaled up, which will pave a new way to the low-cost all-solution processable PeQDs-LEDs.

Ultrathin CsPbX3 Nanowire Arrays with Strong Emission Anisotropy

1D nanowires of all-inorganic lead halide perovskites represent a good architecture for the development of polarization-sensitive optoelectronic devices due to their high absorption efficient, emission yield, and dielectric constants. However, among as-fabricated perovskite nanowires with the lateral dimensions of hundreds nanometers so far, the optical anisotropy is hindered and rarely explored owing to the invalidating of electrostatic dielectric mismatch in the physical dimensions. Here, well-aligned CsPbBr₃ and CsPbCl₃ nanowires with thickness T down to 15 and 7 nm, respectively, are synthesized using a vapor phase van der Waals epitaxial method. Strong emission anisotropy with polarization ratio up to ≈0.78 is demonstrated in the nanowires with T < 40 nm due to the electrostatic dielectric confinement. With the increasing of thickness, the polarization ratio remarkably reduces monotonously to ≈0.17 until T ≈140 nm; and further oscillates in a small amplitude owing to the wave characteristic of light. These findings not only represent a demonstration of perovskite-based polarization-sensitive light sources, but also advance fundamental understanding of their polarization properties of perovskite nanowires.

Realization of Lasing Emission from One Step Fabricated WSe₂ Quantum Dots

Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) quantum dots (QDs) are the vanguard due to their unique properties. In this work, WSe₂ QDs were fabricated via one step ultrasonic probe sonication. Excitation wavelength dependent photoluminescence (PL) is observed from WSe₂ QDs. Room-temperature lasing emission which benefits from 3.7 times enhancement of PL intensity by thermal treatment at ~470 nm was achieved with an excitation threshold value of ~3.5 kW/cm² in a Fabry⁻Perot laser cavity. To the best of our knowledge, this is the first demonstration of lasing emission from TMDCs QDs. This indicates that TMDCs QDs are a superior candidate as a new type of laser gain medium.

Postsynthesis Phase Transformation for CsPbBr3/Rb4PbBr6 Core/Shell Nanocrystals with Exceptional Photostability

Lead halide perovskite nanocrystals (NCs) as promising optoelectronic materials are intensively researched. However, instability is one of the biggest challenges needed to overcome before fulfill their practical applications. To improve their stability, we present a postsynthetic controlled phase transformation of CsPbBr₃ toward CsPbBr₃/Rb₄PbBr₆ core/shell structure triggered by rubidium oleate treatment. The resulting core/shell NCs show exceptional photostability both in solution and on-chip. The solution of CsPbBr₃/Rb₄PbBr₆ NCs can remain over 90% of the initial emission photoluminescence quantum yields after 42 h of intense light-emitting diodes illumination (450 nm, 175 mW/cm²), which is even better than the conventional CdSe/CdS quantum dots whose emission drop to 50% after 18 h under the same condition. We believe that the exceptional photostability should be resulted from the protection of the robust Rb₄PbBr₆ shell on CsPbBr₃ NCs.

All-inorganic perovskite quantum dots stabilized blue phase liquid crystals

All-inorganic perovskite quantum dots (PQDs) have been effectively incorporated in the three-dimensional ordered structure of blue phase liquid crystals (BPLCs) to stabilize the BPLCs. Uniform dispersion, reduced phase transition temperature, widened BP temperature range, dynamic and fast electro-optical response and static optical display of selective reflection mode and photoluminescence mode have been confirmed with a given concentration of PQDs. Such a novel strategy of assembling all-inorganic PQDs in BPLCs shows favorable prospects for wide-range and near room temperature BPLCs, responsive BPLCs, multifunctional display materials and tunable bandgap lasers.

Composition-Graded Cesium Lead Halide Perovskite Nanowires with Tunable Dual-Color Lasing Performance

Cesium lead halide (CsPbX₃ ) perovskite has emerged as a promising low-threshold multicolor laser material; however, realizing wavelength-tunable lasing output from a single CsPbX₃ nanostructure is still constrained by integrating different composition. Here, the direct synthesis of composition-graded CsPbBr_x I_3-x nanowires (NWs) is reported through vapor-phase epitaxial growth on mica. The graded composition along the NW, with an increased Br/I from the center to the ends, comes from desynchronized deposition of cesium lead halides and temperature-controlled anion-exchange reaction. The graded composition results in varied bandgaps along the NW, which induce a blueshifted emission from the center to the ends. As an efficient gain media, the nanowire exerts position-dependent lasing performance, with a different color at the ends and center respectively above the threshold. Meanwhile, dual-color lasing with a wavelength separation of 35 nm is activated simultaneously at a site with an intermediate composition. This position-dependent dual-color lasing from a single nanowire makes these metal halide perovskites promising for applications in nanoscale optical devices.

All-Inorganic Metal Halide Perovskite Nanocrystals: Opportunities and Challenges

The past decade has witnessed the growing interest in metal halide perovskites as driven by their promising applications in diverse fields. The low intrinsic stability of the early developed organic versions has however hampered their widespread applications. Very recently, all-inorganic perovskite nanocrystals have emerged as a new class of materials that hold great promise for the practical applications in solar cells, photodetectors, light-emitting diodes, and lasers, among others. In this Outlook, we first discuss the recent developments in the preparation, properties, and applications of all-inorganic metal halide perovskite nanocrystals, with a particular focus on CsPbX₃, and then provide our view of current challenges and future directions in this emerging area. Our goal is to introduce the current status of this type of new materials to researchers from different areas and motivate them to explore all the potentials.

Exploration of Near-Infrared-Emissive Colloidal Multinary Lead Halide Perovskite Nanocrystals Using an Automated Microfluidic Platform

Hybrid organic-inorganic and fully inorganic lead halide perovskite nanocrystals (NCs) have recently emerged as versatile solution-processable light-emitting and light-harvesting optoelectronic materials. A particularly difficult challenge lies in warranting the practical utility of such semiconductor NCs in the red and infrared spectral regions. In this context, all three archetypal A-site monocationic perovskites-CH₃NH₃PbI₃, CH(NH₂)₂PbI₃, and CsPbI₃-suffer from either chemical or thermodynamic instabilities in their bulk form. A promising approach toward the mitigation of these challenges lies in the formation of multinary compositions (mixed cation and mixed anion). In the case of multinary colloidal NCs, such as quinary Cs _xFA_{1- x}Pb(Br_{1- y}I _y)₃ NCs, the outcome of the synthesis is defined by a complex interplay between the bulk thermodynamics of the solid solutions, crystal surface energies, energetics, dynamics of capping ligands, and the multiple effects of the reagents in solution. Accordingly, the rational synthesis of such NCs is a formidable challenge. Herein, we show that droplet-based microfluidics can successfully tackle this problem and synthesize Cs _xFA_{1- x}PbI₃ and Cs _xFA_{1- x}Pb(Br_{1- y}I _y)₃ NCs in both a time- and cost-efficient manner. Rapid in situ photoluminescence and absorption measurements allow for thorough parametric screening, thereby permitting precise optical engineering of these NCs. In this showcase study, we fine-tune the photoluminescence maxima of such multinary NCs between 700 and 800 nm, minimize their emission line widths (to below 40 nm), and maximize their photoluminescence quantum efficiencies (up to 89%) and phase/chemical stabilities. Detailed structural analysis revealed that the Cs _xFA_{1- x}Pb(Br_{1- y}I _y)₃ NCs adopt a cubic perovskite structure of FAPbI₃, with iodide anions partially substituted by bromide ions. Most importantly, we demonstrate the excellent transference of reaction parameters from microfluidics to a conventional flask-based environment, thereby enabling up-scaling and further implementation in optoelectronic devices. As an example, Cs _xFA_{1- x}Pb(Br_{1- y}I _y)₃ NCs with an emission maximum at 735 nm were integrated into light-emitting diodes, exhibiting a high external quantum efficiency of 5.9% and a very narrow electroluminescence spectral bandwidth of 27 nm.

Robust Subwavelength Single-Mode Perovskite Nanocuboid Laser

On-chip photonic information processing systems require great research efforts toward miniaturization of the optical components. However, when approaching the classical diffraction limit, conventional dielectric lasers with all dimensions in nanoscale are difficult to realize due to the ultimate miniaturization limit of the cavity length and the extremely high requirement of optical gain to overcome the cavity loss. Herein, we have succeeded in reducing the laser size to subwavelength scale in three dimensions using an individual CsPbBr₃ perovskite nanocuboid. Even though the side length of the nanocuboid laser is only ∼400 nm, single-mode Fabry-Pérot lasing at room temperature with laser thresholds of 40.2 and 374 μJ/cm² for one- and two-photon excitation has been achieved, respectively, with the corresponding quality factors of 2075 and 1859. In addition, temperature-insensitive properties from 180 to 380 K have been demonstrated. The physical volume of a CsPbBr₃ nanocuboid laser is only ∼0.49λ³ (where λ is the lasing wavelength in air). Its three-dimensional subwavelength size, excellent stable lasing performance at room temperature, frequency up-conversion ability, and temperature-insensitive properties may lead to a miniaturized platform for nanolasers and integrated on-chip photonic devices in nanoscale.

Two-Photon Absorption and Two-Photon-Induced Gain in Perovskite Quantum Dots

Perovskite quantum dots (PQDs) emerged as a promising class of material for applications in lighting devices, including light emitting diodes and lasers. In this work, we explore nonlinear absorption properties of PQDs showing the spectral signatures and the size dependence of their two-photon absorption (2PA) cross-section, which can reach values higher than 10⁶ GM. The large 2PA cross section allows for low threshold two-photon induced amplified spontaneous emission (ASE), which can be as low as 1.6 mJ/cm². We also show that the ASE properties are strongly dependent on the nanomaterial size, and that the ASE threshold, in terms of the average number of excitons, decreases for smaller PQDs. Investigating the PQDs biexciton binding energy, we observe strong correlation between the increasing on the biexciton binding energy and the decreasing on the ASE threshold, suggesting that ASE in PQDs is a biexciton-assisted process.

Tuning the Optical Properties of CsPbBr3 Nanocrystals by Anion Exchange Reactions with CsX Aqueous Solution

Topotactic anion exchange has been developed to tune the composition and band gap energies of cesium lead halide (CsPbX₃) perovskite nanocrystals (NCs). However, current anion exchange methods either require harsh conditions or take a long time to realize substantial substitution. Here, we present a method to modulate the composition of colloidal CsPbBr₃ NCs through ultrasonication-assisted anion exchange with CsX (X = Cl, I) solution. Efficient anion exchange of CsPbBr₃ NCs with Cl^- or I^- is realized with substitution ratio up to 93% and preservation of the pristine shape and structure of CsPbBr₃ NCs. This anion exchange results in tunable emission, covering the whole visible spectral range, with relatively high photoluminescence quantum yield, narrow emission bandwidths, and good stability. This work provides a facile and efficient way to engineer the properties of halide perovskite NCs and has great potential for large-scale production of compositionally diverse perovskite NCs.

Precise Control of Quantum Confinement in Cesium Lead Halide Perovskite Quantum Dots via Thermodynamic Equilibrium

Cesium lead halide (CsPbX₃) nanocrystals have emerged as a new family of materials that can outperform the existing semiconductor nanocrystals due to their superb optical and charge-transport properties. However, the lack of a robust method for producing quantum dots with controlled size and high ensemble uniformity has been one of the major obstacles in exploring the useful properties of excitons in zero-dimensional nanostructures of CsPbX₃. Here, we report a new synthesis approach that enables the precise control of the size based on the equilibrium rather than kinetics, producing CsPbX₃ quantum dots nearly free of heterogeneous broadening in their exciton luminescence. The high level of size control and ensemble uniformity achieved here will open the door to harnessing the benefits of excitons in CsPbX₃ quantum dots for photonic and energy-harvesting applications.

Solvent-Assisted Surface Engineering for High-Performance All-Inorganic Perovskite Nanocrystal Light-Emitting Diodes

All-inorganic cesium halide perovskite nanocrystals have attracted much interest in optoelectronic applications for the sake of the readily adjustable band gaps, high photoluminescence quantum yield, pure color emission, and affordable cost. However, because of the ineluctable utilization of organic surfactants during the synthesis, the structural and optical properties of CsPbBr₃ nanocrystals degrade upon transforming from colloidal solutions to solid thin films, which plagues the device operation. Here, we develop a novel solvent-assisted surface engineering strategy, producing high-quality CsPbBr₃ thin films for device applications. A good solvent is first introduced as an assembly trigger to conduct assembly in a one-dimensional direction, which is then interrupted by adding a nonsolvent. The nonsolvent drives the adjacent nanoparticles connecting in a two-dimensional direction. Assembled CsPbBr₃ nanocrystal thin films are densely packed and very smooth with a surface roughness of ∼4.8 nm, which is highly desirable for carrier transport in a light-emitting diode (LED) device. Meanwhile, the film stability is apparently improved. Benefiting from this facile and reliable strategy, we have achieved remarkably improved performance of CsPbBr₃ nanocrystal-based LEDs. Our results not only enrich the methods of nanocrystal surface engineering but also shed light on developing high-performance LEDs.

Dendrimer ligands-capped CH3NH3PbBr3 perovskite nanocrystals with delayed halide exchange and record stability against both moisture and water

CH₃NH₃PbBr₃ perovskite nanocrystals (NCs) suffer from poor stability because of their high sensitivity to environmental moisture and water. To solve this problem, previous works mainly focus on embedding perovskite NCs into water-resistant matrix to form large composites (size of microns or larger). As an alternative solution without serious changing of NC size, enhancing the stability of perovskite NCs themselves by ligand engineering is rarely reported. In this work, we used hyperbranched polyamidoamine (PAMAM) dendrimers with two different generations (G0 and G4) to synthesize CH₃NH₃PbBr₃ perovskite NCs with high photoluminescence (PL) quantum yields (QY) above 70% and a new record stability. A novel dendrimers generation-dependent stability of perovskite NCs was observed. The water-resistance time is 18 h (27 h) for perovskite NCs capped by G0 (G4) generation of PAMAM, which is 7 times (11 times) longer than that of traditional oleic acid-capped NCs. Similar PAMAM generation-related stability is also observed in moisture-resistance tests. The stability time against moisture is 500 h (800 h) for G0 (G4) generation of PAMAM-capped perovskite NCs, which is a new record stability time against moisture for CH₃NH₃PbBr₃ perovskite NCs. In addition, our results also indicate that PAMAM ligands outside perovskite NCs can dramatically slow down the speed of halide exchange. Even for the mixture of perovskite NCs with two different halide composition, the original luminescence properties of PAMAM-capped perovskite NCs can retain after mixing. In view of slow halide exchange speed, excellent water and moisture stability, PAMAM dendrimers-capped perovskite NCs and their mixture are available as color conversion single layer in fabrication of light-emitting diodes (LED).

All-inorganic perovskite quantum dot/TiO2 inverse opal electrode platform: stable and efficient photoelectrochemical sensing of dopamine under visible irradiation

CsPbX3 (X = Cl, Br or I) perovskite quantum dots (PQDs) have attracted tremendous attention due to their extraordinarily excellent optical properties. However, there is still an obstacle for their bio-application, which is limited by their water-instability. In this work, we have designed a novel visible light triggered photoelectrochemical (PEC) sensor for dopamine (DA) based on CsPbBr1.5I1.5 PQD immobilized three-dimensional (3D) TiO2 inverse opal photonic crystals (IOPCs). Supported by the TiO2 IOPCs, the water-stability of the PQDs as well as that of the PEC sensor was considerably improved. Furthermore, employed as a photoactive material in PEC sensor, CsPbBr1.5I1.5 PQDs can expand the photocurrent response of the PEC sensor to the whole visible region. In addition, the modulation of the photonic stop band effect of TiO2 IOPCs on the incident light and the emission of PQDs could further enhance the photocurrent response. Such a PEC sensor demonstrates sensitive detection of DA in phosphate buffer saline solution and serum, with a good linear range from 0.1 μM to 250 μM and a low detection limit of approximately 0.012 μM. Our strategy opens an alternative horizon for PQD based PEC sensing, which could be more sensitive, convenient and inexpensive for clinical and biological analysis.

Pick a Color MARIA: Adaptive Sampling Enables the Rapid Identification of Complex Perovskite Nanocrystal Compositions with Defined Emission Characteristics

Recent advances in the development of hybrid organic-inorganic lead halide perovskite (LHP) nanocrystals (NCs) have demonstrated their versatility and potential application in photovoltaics and as light sources through compositional tuning of optical properties. That said, due to their compositional complexity, the targeted synthesis of mixed-cation and/or mixed-halide LHP NCs still represents an immense challenge for traditional batch-scale chemistry. To address this limitation, we herein report the integration of a high-throughput segmented-flow microfluidic reactor and a self-optimizing algorithm for the synthesis of NCs with defined emission properties. The algorithm, named Multiparametric Automated Regression Kriging Interpolation and Adaptive Sampling (MARIA), iteratively computes optimal sampling points at each stage of an experimental sequence to reach a target emission peak wavelength based on spectroscopic measurements. We demonstrate the efficacy of the method through the synthesis of multinary LHP NCs, (Cs/FA)Pb(I/Br)₃ (FA = formamidinium) and (Rb/Cs/FA)Pb(I/Br)₃ NCs, using MARIA to rapidly identify reagent concentrations that yield user-defined photoluminescence peak wavelengths in the green-red spectral region. The procedure returns a robust model around a target output in far fewer measurements than systematic screening of parametric space and additionally enables the prediction of other spectral properties, such as, full-width at half-maximum and intensity, for conditions yielding NCs with similar emission peak wavelength.

In Situ Crystallization Synthesis of CsPbBr3 Perovskite Quantum Dot-Embedded Glasses with Improved Stability for Solid-State Lighting and Random Upconverted Lasing

All-inorganic cesium lead bromide CsPbBr₃ perovskite quantum dots (QDs) are emerging as potential candidates for their applications in optoelectronic devices but they suffer from poor long-term stability due to their high sensitivity to UV irradiation, heat, and especially to moisture. Although great advances in improving stability of perovskite QDs have been achieved by surface modification or encapsulation in polymer and silica, they are not sufficiently refrained from external environment due to nondense structures of these protective layers. In this work, in situ nanocrystallization strategy is developed to directly grow CsPbBr₃ QDs among a specially designed TeO₂-based glass matrix. As a result, QD-embedded glass shows typical bright green emission assigned to exciton recombination radiation and significant improvement of photon/thermal stability and water resistance due to the effective protecting role of dense structural glass. Particularly, ∼90% of emission intensity is even remained after immersing QD-embedded glass in water up to 120 h, enabling them to find promising applications in white-light-emitting device with superior color stability and low-threshold random upconverted laser under ambient air condition.

Spontaneous Self-Assembly of Perovskite Nanocrystals into Electronically Coupled Supercrystals: Toward Filling the Green Gap

Self-assembly of nanoscale building blocks into ordered nanoarchitectures has emerged as a simple and powerful approach for tailoring the nanoscale properties and the opportunities of using these properties for the development of novel optoelectronic nanodevices. Here, the one-pot synthesis of CsPbBr3 perovskite supercrystals (SCs) in a colloidal dispersion by ultrasonication is reported. The growth of the SCs occurs through the spontaneous self-assembly of individual nanocrystals (NCs), which form in highly concentrated solutions of precursor powders. The SCs retain the high photoluminescence (PL) efficiency of their NC subunits, however also exhibit a redshifted emission wavelength compared to that of the individual nanocubes due to interparticle electronic coupling. This redshift makes the SCs pure green emitters with PL maxima at ≈530-535 nm, while the individual nanocubes emit a cyan-green color (≈512 nm). The SCs can be used as an emissive layer in the fabrication of pure green light-emitting devices on rigid or flexible substrates. Moreover, the PL emission color is tunable across the visible range by employing a well-established halide ion exchange reaction on the obtained CsPbBr3 SCs. These results highlight the promise of perovskite SCs for light emitting applications, while providing insight into their collective optical properties.

Low-Saturation-Intensity, High-Photostability, and High-Resolution STED Nanoscopy Assisted by CsPbBr3 Quantum Dots

Stimulated emission depletion (STED) nanoscopy is one of the most promising super-resolution imaging techniques for microstructure imaging. Commercial CdSe@ZnS quantum dots are used as STED probes and ≈50 nm lateral resolution is obtained. Compared with other quantum dots, perovskite CsPbBr₃ nanoparticles (NPs) possess higher photoluminescence quantum yield and larger absorption cross-section, making them a more effective probe for STED nanoscopy. In this study, CsPbBr₃ NPs are used as probes for STED nanoscopy imaging. The fluorescence intensity of the CsPbBr₃ sample is hardly weakened at all after 200 min irradiation with a 39.8 mW depletion laser, indicating excellent photobleaching resistance of the CsPbBr₃ NPs. The saturation intensity of the CsPbBr₃ NPs is extremely low and estimated to be only 0.4 mW (0.126 MW cm^-2 ). Finally, an ultrahigh lateral resolution of 20.6 nm is obtained for a single nanoparticle under 27.5 mW STED laser irradiation in CsPbBr₃ -based STED nanoscopy imaging, which is a tenfold improvement compared with confocal microscopy. Because of its high fluorescence stability and ultrahigh resolution under lower depletion power, CsPbBr₃ -assisted STED nanoscopy has great potential to investigate microstructures that require super-resolution and long-term imaging.

Phonon mode transformation in size-evolved solution-processed inorganic lead halide perovskite

Recently, lead halide perovskites have attracted significant scientific attention in the fields of photovoltaics, light emitting diodes, lasers, photo-detectors and other optoelectronic functional devices. The most stable crystal form of lead halide perovskites is the cube, including nano-cube and micro-cube, which hold great promise as functional materials due to their combination of unique optoelectronic properties and versatility through colloidal synthesis. Herein, we report the solution-processed synthesis of pure inorganic lead halide nano-cubes- and micro-cubes-based colloidal perovskites. The different size of cubes either into nano-cube or micro-cube are demonstrated that their phonon mode transformation which means the perovskite crystal structure phase change cross the nano-cube to micro-cube. The solution-processed colloidal synthesis method and phonon-mode transformation from nano-cube to micro-cube make pure inorganic lead halide perovskite an ideal platform for fundamental optoelectronic studies and the investigation of functional devices.

Inkjet printable-photoactive all inorganic perovskite films with long effective photocarrier lifetimes

Photoactive perovskite quantum dot films, deposited via an inkjet printer, have been characterized by x-ray diffraction and x-ray photoelectron spectroscopy. The crystal structure and bonding environment are consistent with CsPbBr₃ perovskite quantum dots. The current-voltage (I-V) and capacitance-voltage (C-V) transport measurements indicate that the photo-carrier drift lifetime can exceed 1 ms for some printed perovskite films. This far exceeds the dark drift carrier lifetime, which is below 50 ns. The printed films show a photocarrier density 10⁹ greater than the dark carrier density, making these printed films ideal candidates for application in photodetectors. The successful printing of photoactive-perovskite quantum dot films of CsPbBr₃, indicates that the rapid prototyping of various perovskite inks and multilayers is realizable.

Ligand removal and photo-activation of CsPbBr3 quantum dots for enhanced optoelectronic devices

Perovskite quantum dots have recently emerged as a promising light source for optoelectronic applications. However, integrating them into devices while preserving their outstanding optical properties remains challenging. Due to their ionic nature, perovskite quantum dots are extremely sensitive and degrade on applying the simplest processes. To maintain their colloidal stability, they are surrounded by organic ligands; these prevent efficient charge carrier injection in devices and have to be removed. Here we report on a simple method, where a moderate thermal process followed by exposure to UV in air can efficiently remove ligands and increase the photo-luminescence of the room temperature synthesized perovskite quantum dot thin films. Annealing is accompanied by a red shift of the emission wavelength, usually attributed to the coalescence and irreversible degradation of the quantum dots. We show that it is actually related to the relaxation of the quantum dots upon the ligand removal, without the creation of non-radiative recombining defects. The quantum dot surface, as devoid of ligands, is subsequently photo-oxidized and smoothened upon exposure to UV in air, which drastically enhances their photo-luminescence. This adequate combination of treatments improves by more than an order of magnitude the performances of perovskite quantum dot light emitting diodes.

Color-Tunable ZnO/GaN Heterojunction LEDs Achieved by Coupling with Ag Nanowire Surface Plasmons

Color-tunable light-emitting devices (LEDs) have a great impact on our daily life. Herein, LEDs with tunable electroluminescence (EL) color were achieved via introducing Ag nanowires surface plasmons into p-GaN/n-ZnO film heterostructures. By optimizing the surface coverage density of coated Ag nanowires, the EL color was changed continuously from yellow-green to blue-violet. Transient-state and temperature-variable fluorescence emission characterizations uncovered that the spontaneous emission rate and the internal quantum efficiency of the near-UV emission were increased as a consequence of the resonance coupling interaction between Ag nanowires surface plasmons and ZnO excitons. This effect induces the selective enhancement of the blue-violet EL component but suppresses the defect-related yellow-green emission, leading to the observed tunable EL color. The proposed strategy of introducing surface plasmons can be further applied to many other kinds of LEDs for their selective enhancement of EL intensity and effective adjustment of the emission color.

One-Step Preparation of Long-Term Stable and Flexible CsPbBr3 Perovskite Quantum Dots/Ethylene Vinyl Acetate Copolymer Composite Films for White Light-Emitting Diodes

CsPbBr₃ perovskite quantum dots (PQDs)/ethylene vinyl acetate (EVA) composite films were prepared via a one-step method; on the basis of this, both supersaturated recrystallization of CsPbBr₃ PQDs and dissolution of EVA were realized in toluene. The prepared films display outstanding green-emitting performance with high color purity of 92% and photoluminescence (PL) quantum yield of 40.5% at appropriate CsPbBr₃ PQD loading. They possess long-term stable luminescent properties in the air and in water, benefiting from the effective protection of CsPbBr₃ PQDs by the EVA matrix. Besides, the prepared CsPbBr₃ PQDs/EVA films are flexible enough to be repeatedly bent for 1000 cycles while keeping unchanged the PL intensity. The optical properties of the CsPbBr₃ PQDs/EVA films in white light-emitting diodes were also studied by experiments and theoretical simulation. Overall, facile preparation process, good long-term stability, and high flexibility allow our green-emitting CsPbBr₃ PQDs/EVA films to be applied in lighting applications and flexible displays.