All-inorganic Lead Halide Perovskite Research Articles

Solvent‐Mediated Structural Evolution in Colloidal Lead Halide Perovskite Nanocrystals Self‐Assembly (Adv. Mater. Interfaces 19/2022)

Solvent-Mediated Evolution of Colloidal Lead Halide Perovskite Nanocrystals In article number 2200187, Linqi Chen, Hongxing Dong, Long Zhang, and co-workers demonstrate a molecular scale mechanism of solvent-mediated evolution of all-inorganic lead halide perovskite nanocrystals (NCs). By affecting the intermolecular forces between aliphatic ligands on adjacent NCs and regulating the competition between complex bond energy in colloidal NCs system, solvent molecules regulate the self-assembly of ligand-stabilized perovskite NCs and NC arrays and nanowires are freely obtained.

Recent Progress in Lanthanide-Doped Inorganic Perovskite Nanocrystals and Nanoheterostructures: A Future Vision of Bioimaging

All-inorganic lead halide perovskite nanocrystals have great potential in optoelectronics and photovoltaics. However, their biological applications have not been explored much owing to their poor stability and shallow penetration depth of ultraviolet (UV) excitation light into tissues. Interestingly, the combination of all-inorganic halide perovskite nanocrystals (IHP NCs) with nanoparticles consisting of lanthanide-doped matrix (Ln NPs, such as NaYF4:Yb,Er NPs) is stable, near-infrared (NIR) excitable and emission tuneable (up-shifting emission), all of them desirable properties for biological applications. In addition, luminescence in inorganic perovskite nanomaterials has recently been sensitized via lanthanide doping. In this review, we discuss the progress of various Ln-doped all-inorganic halide perovskites (LnIHP). The unique properties of nanoheterostructures based on the interaction between IHP NCs and Ln NPs as well as those of LnIHP NCs are also detailed. Moreover, a systematic discussion of basic principles and mechanisms as well as of the recent advancements in bio-imaging based on these materials are presented. Finally, the challenges and future perspectives of bio-imaging based on NIR-triggered sensitized luminescence of IHP NCs are discussed.

Concentration dependence of photoluminescence properties and exciton dynamics in Mn:CsPb(BrCl)3 quantum dots

All-inorganic lead halide perovskite quantum dots (IPQDs) display some intriguing magnetic, electronic, and optical properties by introducing a transition metal Mn element. In this Letter, Mn-doped CsPb(BrCl)3 IPQDs with a cubic structure have been synthesized by the hot injection method. What make us excited is that the photoluminescence properties of a fixed ensemble of Mn-doped CsPb(BrCl)3 IPQDs systematically depend on the varying concentration. This experimental phenomenon can be well explained by the quantitative model based on photon reabsorption. The results combining experiments with theoretical models indicate that the photon reabsorption is of paramount importance in the analysis of the luminescence properties of colloidal quantum dots especially at high concentrations. Further analysis based on time-resolved fluorescence and transient absorption spectroscopy reveals the effect of the solution concentration on the Mn-doped CsPb(BrCl)3 IPQD exciton dynamics. The results suggest that exciton energy transfer can take place both inside and between IPQDs and also can be enhanced by increasing the concentration of a Mn-doped CsPb(BrCl)3 IPQD solution. These results are of great significance to accurately interpret and control the luminescence properties of IPQDs.

Synthesis of highly luminescent CsPbBr3@Cs4PbBr6 nanocrystals via ligand-assisted reaction

All-inorganic lead halide perovskite nanocrystals (NCs) have attracted enormous attention owing to their excellent optical properties such as ultrahigh photoluminescence quantum yield (PLQY), narrow full width at half maximum (FWHM) and broad emission spectra tunability. In this study, we reported the synthesis of colloidal perovskite NCs based on CsPbBr3@Cs4PbBr6 composite structure. With the assistance of Tetraoctylammonium bromide (TOAB) ligands, the prepared CsPbBr3@Cs4PbBr6 NCs show high PLQY of 94.7% and enhanced stability. The crystal morphology and phase structure of the CsPbBr3@Cs4PbBr6 NCs were investigated by HRTEM and XRD measurements. In addition, the crystal morphology of CsPbBr3@Cs4PbBr6 NCs presents cubic and circular particles with an average size of 9.3 nm. Compared with CsPbBr3 NCs, the diphase CsPbBr3@Cs4PbBr6 composite materials can perform higher optical properties due to the in-situ passivation of the generated Cs4PbBr6 NCs. Furthermore, the fabricated LED device exhibits bright white light emission with a color coordinate of (0.335, 0.337), the corresponding color temperature of 5390 K and a color rendering index of 82.1 under the injection current of 30 mA. These results demonstrate that the obtained CsPbBr3@Cs4PbBr6 NCs have a potential application in white light-emitting and display devices.

Luminescent and ultrastable perovskite-acrylate based elastomers with excellent stretchability and self-healing capability for flexible backlight display

All-inorganic lead halide perovskite nanocrystals (NCs) have received considerable attention due to their exceptional optoelectronic characteristics and photovoltaic performance, but their practical applications are restricted by their poor stability. Integrating multifunctionality such as high stability, outstanding flexibility, stretchability and self-healing capability has also been highly desired for flexible full-color displays, soft optical devices, and wearable applications. Here, we developed a facile one-pot photopolymerization strategy to produce highly stable self-healing CsPbBr3-based elastomers with outstanding flexibility, scalability, and stretchability. The obtained perovskite NCs (∼10 nm; PLQY of 78%) were capped and passivated with bifunctional methacrylic acid ligands, which provided free double bonds on their surface. The CsPbBr3-based elastomers were obtained via the photo-induced copolymerization of functionalized CsPbBr3 NCs with methyl methacrylate (MMA) and n-butyl acrylate (BA) at room temperature. This yielded homogenous CsPbBr3 nanocrystals (∼10 nm) dispersed in the copolymer, which displayed a high photoluminescence quantum yield (PLQY > 70%). Versatile and specific luminescent shapes and patterns could be fabricated from the CsPbBr3-based elastomers by regulating the constituent content, reaction time, or molding process. The obtained CsPbBr3-based elastomers exhibited high air and water stability, high stretchability (∼1300% elongation), tensile recovery (∼100%), and excellent self-healing capability, which also permitted twisting or bending. This facile photopolymerization strategy greatly expands the methods for fabricating highly stable perovskite materials with excellent stretchability and self-healing properties for use in flexible optoelectronic devices.

Detailed Structural Features of the Perovskite-Related Halide RbPbI3 for Solar Cell Applications.

All-inorganic lead halide perovskites like CsPbBr3, CsPbI3, or RbPbI3 are good replacements for the classical hybrid organic–inorganic perovskites like CH3NH3PbI3, susceptible to fast degradation in the presence of humid air. They also exhibit outstanding light absorption properties suitable for solar energy applications. Here, we describe the synthesis of RbPbI3 by mechanochemical procedures with green credentials, avoiding toxic or expensive organic solvents; this specimen exhibits excellent crystallinity. We report neutron powder diffraction data, essential to revisit some subtle structural features around room temperature (200–400 K). In all these regimes, the orthorhombic Pnma crystal structure is characterized by the presence along the b direction of the crystal of double rows of edge-sharing PbI6 octahedra. The lone electron pairs of Pb2+ ions have a strong stereochemical effect on the PbI6 octahedral distortion. The relative covalency of Rb–I versus Pb–I bonds shows that the Pb–I-related motions are more rigid than Rb–I-related vibrations, as seen in the Debye temperatures from the evolution of the anisotropic displacements. The optical gap, measured by diffuse reflectance UV–vis spectroscopy, is ∼2.51 eV and agrees well with abinitio calculations. The thermoelectric Seebeck coefficient is 3 orders of magnitude larger than that of other halide perovskites, with a value of ∼117,000 μV·K–1 at 460 K.

Quantifying Efficiency Limitations in All-Inorganic Halide Perovskite Solar Cells.

While halide perovskites have excellent optoelectronic properties, their poor stability is a major obstacle toward commercialization. There is a strong interest to move away from organic A-site cations such as methylammonium and formamidinium toward Cs with the aim of improving thermal stability of the perovskite layers. While the optoelectronic properties and the device performance of Cs-based all-inorganic lead-halide perovskites are very good, they are still trailing behind those of perovskites that use organic cations. Here, the state-of-the-art of all-inorganic perovskites for photovoltaic applications is reviewed by performing detailed meta-analyses of key performance parameters on the cell and material level. Key material properties such as carrier mobilities, external photoluminescence quantum efficiency, and photoluminescence lifetime are discussed and what is known about defect tolerance in all-inorganic is compared relative to hybrid (organic-inorganic) perovskites. Subsequently, a unified approach is adopted for analyzing performance losses in perovskite solar cells based on breaking down the losses into several figures of merit representing recombination losses, resistive losses, and optical losses. Based on this detailed loss analysis, guidelines are eventually developed for future performance improvement of all-inorganic perovskite solar cells.

Solvothermal synthesis of perovskite CsPbCl3 nanoplates and improved photoluminescence performance through postsynthetic treatment

The controllable synthesis of two-dimensional all-inorganic lead halide perovskite (CsPbX3, X = Cl, Br and I) nanoplates (NPLs) has attracted wide attention of researchers. However, the direct synthesis of high-quality CsPbCl3 NPLs with controllable morphology still faces a challenge. Herein we report a solvothermal method to directly synthesize CsPbCl3 NPLs. By varying solvothermal reaction time, the thickness of the NPLs has be successfully adjusted from 2.8 to 3.6 nm, and the red shift of the photoluminescence (PL) emission from 391 to 402 nm has been realized. Subsequently, effective post-treatment on the as-prepared CsPbCl3 NPLs using CoCl2 results in the greatly enhancement of PL quantum yield (PLQY) from original 14.09 to final 50.4%, showing the best PLQY among all CsPbCl3 NPLs samples to date. This work not only provides a reliable process for the controllable preparation of CsPbCl3 NPLs, but also supplies more selectivity for the post-treatment of CsPbCl3 nanocrystals using chloride compounds.

Ultra-Stable CsPbX3 @Pyrophosphate Nanoparticles in Water over One Year.

All-inorganic lead halide perovskite (CsPbX3 , X= Cl, Br, I, or their mixture) nanocrystals (NCs) have achieved inspiring advancements in optoelectronic fields but still suffer from poor durability when exposed to environmental stimuli such as water, irradiation and heat. Herein, a strategy of employing pyrophosphate as the inert shell for CsPbX3 NCs is reported. The strong binding between pyrophosphate and CsPbBr3 surface can stabilize the perovskite structure well. The as-obtained core@shell CsPbBr3 @NH4 AlP2 O7 NCs exhibit impressive stability against water and maintain the initial optical properties with negligible change in 400 days. Furthermore, significant improvement of irradiation/thermal resistance is realized due to the protecting role of pyrophosphate. The NCs can retain 100% and ≈90% of the original PL after hundreds of heating/cooling cycles and several hundred hours of UV light irradiation, respectively. As a result, the core@shell products can be directly used for high-resolution inkjet printing, enabling the printed fluorescent information to be resistant under harsh environmental conditions. This work provides a promising way for the synthesis of highly stable encapsulated perovskite NCs and demonstrates a great potential in practical applications.

Probing the effect of a glass network on the synthesis and luminescence properties of composite perovskite glasses [Invited

All-inorganic cesium lead bromide perovskite nanocrystals (PNCs) are highly promising candidates for various optoelectronic and photonic devices. However, poor stability upon exposure to moisture and lead toxicity issues significantly limit their applications. A modern and promising strategy on resolving these issues is the encapsulation of highly luminescent (PNCs) within transparent inorganic oxide glasses. While the encapsulation procedure effect on the development and properties of the so-formed PV-Glasses has been explored in detail, there is lack of understanding the influence of the selected glass composition and network type on the outcome of the synthesis. Herein we report on the synthesis and photoluminescence properties of composite perovskite-glasses upon growing all-inorganic lead halide perovskites within three different types of inorganic oxide glasses. When a silver metaphosphate glass matrix is used it is revealed that the low glass transition temperature of the phosphate glass limits significantly the temperature range of the required post-melting annealing treatment, while the lead salt precursors react with the phosphate entities of the network destroying the stoichiometry of the PNCs. As a result the formation of PNCs is hindered. As a consequence, a double network former borophosphate glass was employed as a suitable host. While annealing treatments at higher temperature were facilitated in this case, it is found that the high silver content becomes an obstacle for the perovskite formation. In view of these findings, cesium lead bromide (CsPbBr3) and cesium lead iodide (CsPbI3) composite perovskite borate glasses were synthesized and found to be suitable hosts. Indeed, such composite glasses exhibit interesting photoluminescence properties that are compared with those of PNCs outside the glass matrix.

Compositional degradation with Br content in Cesium lead halide CsPbBrxI3-x

The inorganic cesium lead halide CsPbX3 (where X ​= ​I, Br, Cl) are reported to possess good stability than that of organic-inorganic hybrid halides. CsPbI3 is reported to have four phases: perovskite black phase (cubic (α), tetragonal (β), orthorhombic(γ)) and non-perovskite yellow orthorhombic (δ). With band gap of ∼ 1.73eV, CsPbI3-α is most suitable phase among all-inorganic lead halide Perovskites. However, in ambient atmosphere (almost instantly) the perovskite black phase convert into non-perovskite yellow orthorhombic phase. At the same time CsPbBr3 remains in the orthorhombic phase at room temperature. Thus, in the present investigation, compositional variation of Br in Cesium lead iodide CsPbBrxI3-x (x ​= ​0.0 to 3.0 ​at the step of 0.5) samples synthesized by cold sintering technique is studied. The XRD patterns showed the orthorhombic phase for CsPbBr3. Further, CsPbBrxI3-x (x ​≤ ​1.0) have shown double phase corresponding to CsPbI3 (Pnma) ​+ ​PbI2 ( R3¯m). However, the compound with 1.5 ≤ x ​< ​3.0 showed the presence of various phases with and without oxygen including the CsPbBr3 (orthorhombic, Pnma) phase which has also been confirmed through UV–visible spectroscopy, impedance and Schottky anomaly. This compositional failure is also suggested by deviation from Vegards law showing volumetric expansion. The role of oxygen vacancy has been probed for the compositional failure for 1.5 ≤ x ​< ​3.0 using XPS characterization and Raman spectroscopy.

Preparation and Energy Storage Performance of Perovskite Luminescent Materials by an Electrochemiluminescence Method

In recent years, metal halide perovskites have become attractive photosensitive materials due to their excellent optoelectronic properties. Due to its good characteristics, perovskites are used in solar photovoltaic power generation, light-emitting diodes, photodetectors, photocatalysis, and sensors and many other fields. Considering the wide application of perovskites and the study of potential bifunctional devices, the application of perovskites in energy storage devices is relatively small, and a small number of studies focus on organic-inorganic hybrid lead-halide perovskites. However, the related energy storage research on all-inorganic lead-halide perovskites with better stability, which has also been widely concerned, is very scarce. And nontoxic all-inorganic nonperovskite has zero research in energy storage. Based on the above situation, this paper selects the lead-free perovskite Cs2AgSbCl6, and two lead halide perovskites with different dimensions, -0-dimensional Cs4PbBr6 and 3-dimensional CsPbBr3, these three all-inorganic perovskites. It was for electrochemical performance testing.

Simple and sustainable synthesis of perovskite-based optoelectronic material: CsPbBr3 nanocrystals via laser ablation in alcohol.

All-inorganic lead halide perovskite nanocrystals (NCs) have shown great potential as emerging semiconducting materials due to their excellent optoelectronic properties. However, syntheses in solution commonly use high temperatures and toxic solvents, which are obstacles for safety and sustainability of the process. In this work, laser ablation in alcohol is proposed as a simple and sustainable, ligand-free, top-down approach to synthesize CsPbBr3 nanocrystals in ambient conditions. The effects of different low boiling point commercial alcohols used as solvents on the optical properties of CsPbBr3 NCs colloidal solutions are investigated. Although in traditional bottom-up synthesis alcohols are usually found to be not appropriate for the synthesis of perovskite NCs, here it is demonstrated that CsPbBr3 orthorhombic nanocrystals with narrow full width half maximum (FWHM < 18 nm), long photoluminescence lifetimes (up to 17.9 ns) and good photoluminescence quantum yield (PLQY up to 15.5%) can be obtained by selecting the dielectric constant and polarity of the alcohol employed for the synthesis.

Optimizing the quasi-equilibrium state of hot carriers in all-inorganic lead halide perovskite nanocrystals through Mn doping: fundamental dynamics and device perspectives.

Hot carrier (HC) cooling accounts for the significant energy loss in lead halide perovskite (LHP) solar cells. Here, we study HC relaxation dynamics in Mn-doped LHP CsPbI3 nanocrystals (NCs), combining transient absorption spectroscopy and density functional theory (DFT) calculations. We demonstrate that Mn2+ doping (1) enlarges the longitudinal optical (LO)–acoustic phonon bandgap, (2) enhances the electron–LO phonon coupling strength, and (3) adds HC relaxation pathways via Mn orbitals within the bands. The spectroscopic study shows that the HC cooling process is decelerated after doping under band-edge excitation due to the dominant phonon bandgap enlargement. When the excitation photon energy is larger than the optical bandgap and the Mn2+ transition gap, the doping accelerates the cooling rate owing to the dominant effect of enhanced carrier–phonon coupling and relaxation pathways. We demonstrate that such a phenomenon is optimal for the application of hot carrier solar cells. The enhanced electron–LO phonon coupling and accelerated cooling of high-temperature hot carriers efficiently establish a high-temperature thermal quasi-equilibrium where the excessive energy of the hot carriers is transferred to heat the cold carriers. On the other hand, the enlarged phononic band-gap prevents further cooling of such a quasi-equilibrium, which facilitates the energy conversion process. Our results manifest a straightforward methodology to optimize the HC dynamics for hot carrier solar cells by element doping.

Direct drop-casting synthesis of all-inorganic lead and lead-free halide perovskite microcrystals for high-performance photodetectors

Direct drop-casting synthesis of all-inorganic lead and lead-free halide perovskite microcrystals for high-performance photodetectors

Highly Tunable Enhancement and Switching of Nonlinear Emission from All-Inorganic Lead Halide Perovskites via Electric Field.

Herein, we demonstrate a highly tunable enhancement and switching of nonlinear emission from all-inorganic metal halide perovskites based on an asymmetrically biased metal-insulator-semiconductor (MIS) structure. We achieve 2 orders of magnitude enhancement of the two-photon-pumped photoluminescence (TPL) from CsPbBr3 microplates with the MIS structure, due to comprehensive effects including localized field effect, trap-filling effect, and collection enhancement. In particular, taking advantage of electric-field-induced passivation/activation of Br vacancies, we realize highly tunable TPL enhancement, ranging from ∼61.2-fold to ∼370.3-fold. Moreover, we demonstrate an efficient modulation of the two-photon-pumped lasing from the MIS structure, which exhibits electric field induced switching with a high on/off ratio of 67:1. This work has opened new avenues for steering carrier transport and nonlinear emission in lead halide perovskites, which shows great promise for realizing high-efficiency and tunable nonlinear nanophotonic devices.

Phase evolution of all-inorganic perovskite nanowires during its growth from quantum dots

All-inorganic lead-halide perovskites have emerged as an exciting material owing to their excellent optoelectronic properties and high stability over hybrid organometallic perovskites. Nanowires of these materials, in particular, have shown great promise for optoelectronic applications due to their high optical absorption coefficient and low defect state density. However, the synthesis of the most promising alpha-Cesium lead iodide (α-CsPbI3) nanowires is challenging as it is metastable and spontaneously converts to a non-perovskite δ-phase. The hot-injection method is one of the most facile, well-controlled, and commonly used approaches for synthesizing CsPbX3 nanostructures. But the exact mechanism of growing these nanowires in this technique is not clear. Here, we show that the hot-injection method produces photoactive phases of quantum dots (QDs) and nanowires of CsPbBr3, and QDs of CsPbI3, but CsPbI3 nanowires are grown in their non-perovskite δ-phase. Monitoring the nanowire growth during the hot-injection technique and through detailed characterization, we establish that CsPbI3 nanowires are formed in the non-perovskite phase from the beginning rather than transforming after its growth from perovskite to a non-perovskite phase. We have discussed a possible mechanism of how non-perovskite nanowires of CsPbI3 grow at the expense of photoactive perovskite QDs. Our findings will help to synthesize nanostructures of all-inorganic perovskites with desired phases, which is essential for successful technological applications.

On-wire axial perovskite heterostructures for monolithic dual-wavelength laser

All-inorganic lead halide perovskites have attracted tremendous attention for their tunable bandgaps, excellent photoluminescence efficiency and robust stability. Here, we report on a direct vapor-phase growth of high-quality CsPbCl3/CsPbI3 axial perovskite heterostructure and multi-heterojunction nanowires using a newly developed magnetic-pulling chemical vapor deposition approach. Microstructural characterization and optical investigations reveal that these structures are crystalline with abrupt heterojunctions. Micro-photoluminescence spectra and mapping at the heterojunctions exhibit dual-wavelength emissions at 417 nm and 698 nm, from the adjacent two disparate perovskites, respectively, further demonstrating the formation of unique heterostructures. Additionally, under a focused laser illumination, asymmetrical waveguide behavior along a single CsPbCl3/CsPbI3 wire is clearly observed. Taking a step further, we fabricated a monolithic dual-wavelength laser using an on-wire axial perovskite heterostructure and successfully realized blue and red emissions (425.5 nm and 687.4 nm). The capability to synthesize on-wire heterostructures represents a major step toward high-integration optoelectronic circuits and nanophotonics.

Defect Passivation via Additive Engineering to Improve Photodetection Performance in CsPbI2Br Perovskite Photodetectors.

Solution-processable all-inorganic lead halide perovskites are under intensive attention due to their potential applications in low-cost high-performance optoelectronic devices such as photodetectors. However, solution processing usually generates structural and chemical defects which are detrimental to the photodetection performance of photodetectors. Here, a polymer additive of polyethylene glycol (PEG) was employed to passivate the localized defects in CsPbI2Br films through the Lewis acid-base interaction. The interfacial defects were passivated efficiently by introducing a trace amount of a PEG additive with a concentration of 0.4 mg mL-1 into the CsPbI2Br precursor solution, as suggested by the significantly reduced trap density of state, which was revealed using thermal admittance spectroscopy. Fourier transform infrared spectrum characterization showed that rather than Cs+ or I-, a Lewis acid-base interaction was established between Pb2+ and PEG to passivate the defects in the CsPbI2Br perovskite, which leads to large suppression of noise current. Both specific detectivity and linear dynamic range improved from 4.1 × 109 Jones and 73 dB to 2.2 × 1011 Jones and 116 dB, respectively. Our work demonstrates the feasibility of employing an environmentally stable polymeric additive PEG to passivate defects for high photodetection performance in all-inorganic perovskite photodetectors.

Enhancing the stability of perovskite quantum dots CsPbX3 (X=Cl, Br, I) by encapsulation in porous Y2O3 nanoparticles for WLED applications

Recently, all-inorganic lead halide perovskite quantum dots (PQDs) have raised great attention for various outstanding properties. Although it is a promising candidate for white light emitting diodes (WLED) application, stability issue remains a challenge. In this work, by using a one-step strategy, we successfully achieved nano-sized Y2O3 nanoparticle assisted stability enhancement of multiple all-inorganic lead halide perovskite. Photostability and environmental stability tests show that all dispersed composites retain most of the fluorescence properties. A WLED is fabricated based on as-prepared CsPbBrI2/P-Y2O3 composite. The Commission Internationale de I'Eclairage (CIE) color coordinates of the fabricated WLED is (0.34, 0.35), which is close to the standard white emission coordinate (0.33, 0.33). The luminous efficiency of as-prepared WLED is 61 lm/W with a color render index (CRI) of 83, demonstrating that CsPbBrI2/P-Y2O3 is potential for application in lighting and display technologies.