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Cesium lead halide (CsPbX 3 , X = Br, I) perovskite nano-crystals (PNCs) with modified compositions were synthesized within boro-germanate glass ceramics to obtain an efficient red color converter for ultra-high definition (UHD) display application. The glass composition and heat treatment conditions were varied to achieve a high photo-luminescence quantum yield (PLQY) under a blue (450 nm) light emitting diode (LED) excitation. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of CsPb(Br/I) 3 PNCs within the glass matrix. A high PLQY of up to 70.5 % was achieved under 450 nm blue LED excitation. The role of composition on the glass structure and PNC formation as well as PL-QY was investigated by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The stability of the CsPb(Br/I) 3 PNC embedded glass (PNEG) against temperature, water, and continuous LED irradiation was examined, and revealed significantly improved photo, chemical and thermal stability compared to colloidal PNCs. Practical feasibility for display applications was demonstrated by fabricating a white LED using the present red PNEG mixed with green CsPbBr 3 PNEG in a remote phosphor-in-silicone structure, showing a wide color gamut of 138.9 % of the NTSC. [ABSTRACT FROM AUTHOR]

Ion-exchange has been widely employed to modify the composition and structure of glasses. In this work, Cs–K ion-exchange was carried out to facilitate the precipitation of cesium lead halide perovskite nanocrystals in the surface layer of glasses. Both Cs 4 PbBr 6 and CsPbBr 3 perovskite nanocrystals and KBr nanocrystals can be precipitated through ion-exchange in nitrate salt. Content of Cs 4 PbBr 6 and CsPbBr 3 perovskite nanocrystals is strongly dependent on the composition of nitrate salt, ion-exchange conditions, and post-thermal annealing. High concentration of Cs in nitrate salt, long ion-exchange duration, and post-thermal annealing are effective to promote the formation of CsPbBr 3 perovskite nanocrystals. Results reported is valuable for the developing of cesium lead halide perovskite nanocrystals embedded glass for light converters. [ABSTRACT FROM AUTHOR]

Perovskite materials offer high-efficiency low-cost solar cells and applications versatility. We report on cesium-based hybrid perovskite solar cells with wavelength-selective properties ranging from 500 nm (UV-VIS) to 800 nm (IR). The band gap tuning was achieved through composition changes of mainly lead(II) iodide PbI2 and lead(II) bromide PbBr2. The optical spectra of the developed materials were studied, including the photoluminescence (PL), optical transparency, X-ray diffraction and external quantum efficiency for samples prepared under different compositions. It was found that a high content of iodine displayed a photoluminescence (PL) peak at 790 nm, whereas a high content of bromine showed a PL peak at 548 nm. The combined composition mixture of PbI2 and PbBr2 can be fine-tuned to prepare materials that absorbed light in the visible range (640–660 nm) or other selective wavelengths in the range from 500 to 800 nm. The illuminated current-voltage characteristics of the solar cells were carried out under the AM 1.5 condition using an ABET solar simulator with a reference solar cell for comparison and control. The average efficiency of the fabricated solar cells ranged from 3.5% to 15.5%, depending on perovskite composition. Wavelength-selective solar cells have potential applications in smart windows, building of integrated PVs and solar-operated greenhouses. [ABSTRACT FROM AUTHOR]

Colloidally synthesized cesium lead halide (CsPbX3; X = Cl, Br, and I) perovskite nanocrystals (PNCs) often suffer from poor ambient and environmental stability conditions, limiting their practical applications. The commonly used surfactant oleylamine is converted to the oleylammonium cation, which pulls out the halide anion from the PNC surface, thus disrupting the structural integrity and stability of the nanocrystal. We developed a simple, completely amine-free colloidal synthesis with a hot injection method under open-atmospheric conditions and introduced bromooctane as a bromine precursor to overcome the above issues. These as-synthesized amine-free PNCs show a photoluminescence quantum yield (PLQY) of around 60%, and the size of PNCs is ∼25 nm. Moreover, these amine-free PNCs were highly stable in colloidal solutions and thin films for more than 5 months under ambient conditions, with 66% of their initial PLQY. In addition, these PNCs show exceptional stability under different environmental conditions, with 44% of the initial PL even after water treatment under 6 h and 28% of the initial PL under ethanol treatment of 120 min. Furthermore, they exhibit excellent photostability for 96 h and retain 36% of their initial PL under ceaseless UV light irradiation at 365 nm (8 W/cm2). In addition, these PNCs have good stability upon heat treatment and maintain 34% of the initial PL upon heating up to 90 °C. Finally, we fabricated a green-emitting down-conversion light-emitting diode (LED) using these amine-free PNCs. Therefore, we envision that these amine-free CsPbBr3 PNCs are perhaps ideal candidates for perovskite-based display applications. [ABSTRACT FROM AUTHOR]

Colloidal cesium lead halide (CsPbX3) perovskite nanocrystals (PNCs) have been shown to exhibit very bright tunable photoluminescence (PL) in the entire visible range and narrow emission widths with composition control. However, challenges afflict the stability of PNCs, which limits their usage in practical applications. Surface passivation with an additional ligand could be an excellent, easy, and facile approach to enhance the photoluminescence and stability of PNCs. To address the issue of stability, we introduce the abundantly available ascorbic acid as a surface capping ligand to achieve high photoluminescence and stability of CsPbX3 PNCs via post-treatment. Ascorbic acid helps in improving the photoluminescence (PL) quantum yield of all halide variant PNCs, particularly CsPbBr3 and CsPb-(Br/I)3 PNCs. With ascorbic acid post-treatment, the luminescence decay profiles are improved with a significant increase in the PL lifetime. As a proof-of-concept, we recorded PL data of untreated and ascorbic acid-treated PNCs for a considerable amount of time and found that ascorbic acid-capped PNCs exhibit exceptional ambient stability, photostability, and thermal stability. The pure CsPbI3 PNCs, which are thermodynamically unstable at room temperature, become ultrastable in the presence of ascorbic acid, where they showed the preservation of the luminescent phase for 55 d since the date of synthesis when stored in open atmospheric conditions. The ascorbic acid-treated CsPb-(Br/I)3 PNCs also exhibited excellent stability with no trace of halide segregation, unlike the as-synthesized mixed halide perovskites, wherein a blue shift of PL is observed with a significant loss in emission. Stabilizing CsPbX3 PNCs of different halide compositions via a simple surface treatment with ascorbic acid could form the basis for futuristic light-emitting applications. [ABSTRACT FROM AUTHOR]

Photodegraded CsPbBr3 perovskite nanocrystals (NCs) can exhibit complete self-recovery following storage in the dark. This behavior results from the readsorption of surface ligands that experienced photoinduced desorption under UV light excitation. In the present work, mixed-halide CsPb-(Cl0.4Br0.6)3, CsPb-(Cl0.2Br0.8)3, and CsPb-(Br0.7I0.3)3 NCs were prepared via ion exchange to evaluate the influence of halide composition on the photodegradation and self-recovery of NCs. Partially substituting Cl– for Br– enhanced the photoactivation, which improved the photoluminescence properties by optimizing the adsorption state of the surface ligands during light excitation. In contrast, partially substituting I– for Br– reduced the stability of the cubic crystal structure, thus subjecting the NCs to irreversible degradation (likely including a partial phase transition) and preventing their self-recovery. Cycle tests confirmed the reversibility of the photodegradation/self-recovery of CsPbBr3 NCs; however, this behavior was disturbed by irreversible surface oxidation reactions when the sample was exposed to ambient air. Therefore, it was concluded that ambient air must be excluded to effectively take advantage of the self-recovery phenomenon for practical applications. [ABSTRACT FROM AUTHOR]

Perovskite materials offer high-efficiency low-cost solar cells and applications versatility. We report on cesium-based hybrid perovskite solar cells with wavelength-selective properties ranging from 500 nm (UV-VIS) to 800 nm (IR). The band gap tuning was achieved through composition changes of mainly lead(II) iodide PbI2 and lead(II) bromide PbBr2. The optical spectra of the developed materials were studied, including the photoluminescence (PL), optical transparency, X-ray diffraction and external quantum efficiency for samples prepared under different compositions. It was found that a high content of iodine displayed a photoluminescence (PL) peak at 790 nm, whereas a high content of bromine showed a PL peak at 548 nm. The combined composition mixture of PbI2 and PbBr2 can be fine-tuned to prepare materials that absorbed light in the visible range (640–660 nm) or other selective wavelengths in the range from 500 to 800 nm. The illuminated current-voltage characteristics of the solar cells were carried out under the AM 1.5 condition using an ABET solar simulator with a reference solar cell for comparison and control. The average efficiency of the fabricated solar cells ranged from 3.5% to 15.5%, depending on perovskite composition. Wavelength-selective solar cells have potential applications in smart windows, building of integrated PVs and solar-operated greenhouses.

Cesium lead halide (CsPbX 3 , X = Br, Cl, and I) nanocrystals (NCs) are widely concerned and applied in many fields due to the excellent photoelectric performance. However, the toxicity of Pb and the loss of luminescence in water limit its application in vivo. A stable perovskite nanomaterial with good bioimaging properties is developed by incorporating europium (Eu) in CsPbX 3 NCs followed with the surface coating of silica (SiO 2 ) shell (CsPbX 3 :Eu@SiO 2 ). Through the surface coating of SiO 2 , the luminescence stability of CsPbBr 3 in water is improved and the leakage of Pb 2+ is significantly reduced. In particular, Eu doping inhibits the photoluminescence quantum yield reduction of CsPbBr 3 caused by SiO 2 coating, and further reduces the release of Pb 2+ . CsPbBr 3 :Eu@SiO 2 nanoparticles (NPs) show efficient luminescence in water and good biocompatibility to achieve cell imaging. More importantly, CsPb(ClBr) 3 :Eu@SiO 2 NPs are obtained by adjusting the halogen components, and green light and blue light are realized in zebrafish imaging, showing good imaging effect and biosafety. The work provides a strategy for advanced perovskite nanomaterials toward biological practical application., (© 2024 Wiley‐VCH GmbH.)

Colloidal perovskite nanocrystals comprised of all inorganic cesium lead halide (CsPbX3, X = Cl, Br, I or a mixture thereof) have potential as optical gain materials due to their high luminescence efficiency. In this work, cesium lead halide nanocrystals are continuously synthesized via a microreactor system consisting of poly(tetrafluoroethylene) (PTFE) capillaries. The synthesized nanocrystals possess excellent optical properties, including a full width at half maximum of 19–35 nm, high fluorescence quantum yield of 47.8–90.55%, and photoluminescence emission in the range of 450–700 nm. For the same precursor concentrations, the photoluminescence emission peak generally increases with increasing reaction temperature, revealing a controllable temperature effect on the photoluminescence characteristics of the synthesized nanocrystals. For quantum dots synthesized with a Br/I ratio of 1:3, a slight blue shift was observed for reaction temperatures greater than 100 °C. This PTFE-based microreactor system provides the unique capability of continuously synthesizing high-quality perovskite nanocrystals that emit over the full visible spectrum with applications ranging from displays and optoelectronic devices.

Cesium lead halide nanostructures have highly tunable optical and optoelectronic properties. Establishing precise control in forming perovskite single-crystal nanostructures is key to unlocking the full potential of these materials. However, studying the growth kinetics of colloidal cesium lead halides is challenging due to their sensitivity to light, electron beam, and environmental factors like humidity. In this study, in situ observations of CsPbBr 3 -particle dynamics were made possible through extremely low dose liquid cell transmission electron microscopy, showing that oriented attachment is the dominant pathway for the growth of single-crystal CsPbBr 3 architectures from primary nanocubes. In addition, oriented assembly and fusion of ligand-stabilized cubic CsPbBr 3 nanocrystals are promoted by electron beam irradiation or introduction of polar additives that both induce partial desorption of the original ligands and polarize the nanocube surfaces. These findings advance our understanding of cesium lead halide growth mechanisms, aiding the controlled synthesis of other perovskite nanostructures.

Recently, lead halide‐based perovskites have become one of the hottest topics in photovoltaic research because of their excellent optoelectronic properties. Among them, organic‐inorganic hybrid perovskite solar cells (PSCs) have made very rapid progress with their power conversion efficiency (PCE) now at 23.7 %. However, the intrinsically unstable nature of these materials, particularly to moisture and heat, may be a problem for their long‐term stability. Replacing the fragile organic group with more robust inorganic Cs+ cations forms the cesium lead halide system (CsPbX3, X is halide) as all‐inorganic perovskites which are much more thermally stable and often more stable to other factors. From the first report in 2015 to now, the PCE of CsPbX3‐based PSCs has abruptly increased from 2.9 % to 17.1 % with much enhanced stability. In this Review, we summarize the field up to now, propose solutions in terms of development bottlenecks, and attempt to boost further research in CsPbX3 PSCs. [ABSTRACT FROM AUTHOR]

Recently, inorganic perovskite CsPbI2Br has gained much attention for photovoltaic applications owing to its excellent thermal stability. However, low device performance and high open‐voltage loss, which are the result of its intrinsic trap states, are hindering its progress. Herein, planar CsPbI2Br solar cells with enhanced performance and stability were demonstrated by incorporating rubidium (Rb) cations. The Rb‐doped CsPbI2Br film exhibited excellent crystallinity, pinhole‐free surface morphology, and enhanced optical absorbance. By using low‐cost carbon electrodes to replace the organic hole‐transportation layer and metal electrode, an excellent efficiency of 12 % was achieved with a stabilized efficiency of over 11 % owing to the suppressed trap states and recombination in the CsPbI2Br film. Additionally, the annealing temperature for the Rb‐doped CsPbI2Br film could be as low as 150 °C with a comparable high efficiency over 11 %, which is one of the best efficiencies reported for hole‐transporting‐layer‐free all‐inorganic perovskite solar cells. These results could provide new opportunities for high‐performance and stable inorganic CsPbI2Br solar cells by employing A‐site cation substitution. Defect passivation: All‐inorganic carbon‐based perovskite solar cells (PSCs), with Rb‐doped CsPbI2Br as the absorber layer, exhibit improved efficiency and enhanced stability compared with PSCs with pristine CsPbI2Br owing to the effectiveness of Rb incorporation in passivating defects states. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • We investigate the photoluminescence properties of the Cs 4 PbBr 6 quantum dots. • They have stable intrinsic luminescence spanning from 340 to 378 nm spectral region. • The studies reveal that there is remarkable quantum confinement effect in these QDs. • The large exciton binding energy explains strong room-temperature exciton emission. Abstract Cesium lead halides are novel and superior optoelectronic materials. Unlike the cases of the widely investigated cubic CsPbXr 3 (X = Cl, Br, or I) nanocrystals, people know little about the optical properties of the "zero-dimensional perovskite" Cs 4 PbX 6 nanocrystals. We study the photoluminescence properties of the Cs 4 PbBr 6 quantum dots (QDs) with sizes of only a few nanometers. They exhibit stable wavelength-tunable (from 340 to 378 nm) luminescence stemming from quasi-self-trapped excitons. The spectral characterizations in conjunction with first-principles calculations reveal there is remarkable quantum confinement effect in the Cs 4 PbBr 6 QDs. The large exciton binding energy obtained from both calculation and experiment explains why the trigonal Cs 4 PbX 6 QDs have strong exciton-related absorption and emission at room temperature. This family of wide-gap trigonal cesium lead halide QDs with intrinsic near-UV luminescence have potential applications in short-wavelength photonic nanodevices. [ABSTRACT FROM AUTHOR]

As a promising material for optoelectronic devices, cesium lead halide perovskite nanocrystals have attracted wide attention recently. However, the fast anion exchange among CsPbX 3 is a problem for applications (e.g., light emitting diode, LED) that require different colors. In this work, we report the large-scale synthesis of ultrathin cesium lead bromide (CsPbBr 3 ) nanoplates (NPs) of tunable edge length and thickness via a simple one-pot colloidal approach. The thickness of NPs can be precisely tuned in a monolayer level by varying the reaction kinetics. The high-quality ultrathin NPs can be prepared in large scale of 0.25 L/batch. The ultrathin CsPbBr 3 NPs emit blue light due to the strong quantum confinement effect, in contrast to the green emission of bulk CsPbBr 3 . For the first time, a blue LED device has been successfully fabricated by using ultrathin CsPbBr 3 NPs as the active layer. The use of CsPbBr 3 perovskite as the emitting layer for blue LED may promote the development of next-generation LEDs and displays. [ABSTRACT FROM AUTHOR]

In this work, the pseudohalide thiocyanate has been demonstrated as a promising alternative to the halide anion to engineer optoelectronic properties of inorganic/organic hybrid perovskites because it exhibits better chemical stability than the halide anion. Previous reports have suggested that the ionic radii and electronegativity of SCN− is close to that of I−; the SCN− doped CH3NH3PbI3 exhibited similar optical properties as pure CH3NH3PbI3. Consequently, it was expected that doping of CsPbBr3 perovskite with SCN− would result in band gap narrowing. Interestingly, the photoluminescent all-inorganic CsPbBr3 perovskite nanocrystals exhibit an abnormal blue shift in optical properties and improvement of the crystallinity when successfully doped by SCN−. Combined experimental and theoretical investigations revealed that doping of the CsPbBr3 perovskite with the rod-like SCN− anion introduced disorder in the crystal lattice, leading to its expansion, and impacted the electronic structure of the perovskite with band gap broadening. [ABSTRACT FROM AUTHOR]

The formation of cesium lead halide perovskite nanocrystals are very effortless due to its extremely fast reaction kinetics. Herein, we present simple hot-inject approach and anion exchange reaction to fabricate all inorganic colloidal CsPbX 3 perovskite nanocrystals (NCs). The colloidal CsPbX 3 NCs with controlling-size exhibit the characteristics of the high luminescent intensity, superior quantum yields (QY, above 69%) and the narrow-band emission tuning, the bandgap energies and emission spectra are readily tunable over the entire visible spectral region of 425–710 nm. Moreover, the third-order nonlinear optical properties of all inorganic colloidal perovskite nanocrystals (CsPbCl 3 , CsPbBr 3 , CsPbI 3 ) were measured using the Z-scan technique, indicating excellent third-order optical nonlinearities. Nonlinear optical susceptibilities reaching to 3.78 × 10 −11 esu for CsPbBr 3 NCs, figure of merit is achieving above 5 for CsPbI 3 NCs. These interesting results demonstrate that the as-prepared all inorganic colloidal CsPbX 3 perovskite nanocrystals are expected to hold great promise for application on nonlinear optoelectronic devices. [ABSTRACT FROM AUTHOR]

We report a novel CsX-stripping mechanism that enables the efficient chemical transformation of nonluminescent Cs4PbX6 (X = Cl, Br, I) nanocrystals (NCs) to highly luminescent CsPbX3 NCs. During the transformation, Cs4PbX6 NCs dispersed in a nonpolar solvent are converted into CsPbX3 NCs by stripping CsX through an interfacial reaction with water in a different phase. This process takes advantage of the high solubility of CsX in water as well as the ionic nature and high ion diffusion property of Cs4PbX6 NCs, and produces monodisperse and air-stable CsPbX3 NCs with controllable halide composition, tunable emission wavelength covering the full visible range, narrow emission width, and high photoluminescent quantum yield (up to 75%). An additional advantage is that this is a clean synthesis as Cs4PbX6 NCs are converted into CsPbX3 NCs in the nonpolar phase while the byproduct of CsX is formed in water that could be easily separated from the organic phase. The as-prepared CsPbX3 NCs show enhanced stability against moisture because of the passivated surface. Our finding not only provides a new pathway for the preparation of highly luminescent CsPbX3 NCs but also adds insights into the chemical transformation behavior and stabilization mechanism of these emerging perovskite nanocrystals. [ABSTRACT FROM AUTHOR]

Recently, all-inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) perovskite nanocrystals have drawn much attention because of their outstanding photophysical properties and potential applications. In this work, a simple and efficient solvothermal approach to prepare CsPbX3 nanocrystals with tunable and bright photoluminescent (PL) properties, controllable composition, and morphology is presented. CsPbX3 nanocubes are successfully prepared with bright emission high PL quantum yield up to 80% covering the full visible range and narrow emission line widths (from 12 to 36 nm). More importantly, ultrathin CsPbX3 (X = Cl/Br, Br, and Br/I) nanowires (with diameter as small as ≈2.6 nm) can be prepared in a very high morphological yield (almost 100%). A strong quantum confinement effect is observed in the ultrathin nanowires, in which both the absorption and emission peaks shift to shorter wavelength range compared to their bulk bandgap. The reaction parameters, such as temperature and precursors, are varied to investigate the growth process. A white light-emitting device prototype device with wide color gamut covering up to 120% of the National Television System Committee standard has been demonstrated by using CsPbBr3 nanocrystals as the green light source. The method in this study provides a simple and efficient way to prepare high-quality CsPbX3 nanocrystals. [ABSTRACT FROM AUTHOR]

Thermally unstable nature of hybrid organic-inorganic perovskites has been a major obstacle to fabricating the long-term operational device. A cesium lead halide perovskite has been suggested as an alternative light absorber, due to its superb thermal stability. However, the phase instability and poor performance are hindering the further progress. Here, cesium lead halide perovskite solar cells with enhanced performance and stability are demonstrated via incorporating potassium cations. Based on Cs0.925K0.075PbI2Br, the planar-architecture device achieves a power conversion efficiency of 10.0%, which is a remarkable record in the field of inorganic perovskite solar cells. In addition, the device shows an extended operational lifetime against air. Our research will stimulate the development of cesium lead halide perovskite materials for next-generation photovoltaics. [ABSTRACT FROM AUTHOR]

The fast kinetics of all-inorganic CsPbX 3 (X = Cl, Br, or I) nanocrystal growth entail that many synthetic strategies for structural control established in other semiconductor systems do not apply. Rather, products are often determined by thermodynamic factors, limiting the range of synthetic outcomes and functionality. In this study, we show how reaction kinetics are significantly slowed if nanocrystals are prepared using a dual injection strategy that moderates the crucial interaction between cesium and halide during nucleation and growth. The result is highly uniform nanorod or cuboid nanocrystals with a controllable size and aspect ratio across the quantum confinement regime, obtainable for both pure and mixed halide compositions. Further, the crystal lattice is continuously tunable between the tetragonal ( I 4/ mcm ) and orthorhombic ( Pbnm ) phases, independent of the overall nanorod morphology, enabling significantly more sophisticated structure-property relationships that can be tailored during this kinetically controlled synthesis.

Herein, we develop a novel strategy for preparing all-inorganic cesium lead halide (CsPbX 3 , X = Cl, Br, I) perovskite nanocrystals (NCs)@Zn-based metal-organic framework (MOF) composites through interfacial synthesis. The successful embedding of fluorescent perovskite NCs in Zn-MOFs is due to the in situ confined growth, which is attributed to the re-nucleation of water-triggered phase transformation from Cs 4 PbBr 6 to CsPbBr 3 . The controllable synthesis of mixed-halide based composites with various emission wavelength can be achieved by adding the desired amount of halide (Cl or I) salts in the re-nucleation process. More importantly, the anion exchange reaction is inhibited among various composites with different halogen atoms by being trapped in MOFs. Besides, a white light-emitting diode (WLED) is produced using a blue LED chip with the green-emitting and red-emitting composites, which has a color coordinate of (0.3291, 0.3272) and a wide color gamut. This work provides a novel route to achieving perovskite NCs growth in MOFs, which also can be extended to the other NCs embedded in frames as well., (© 2022 IOP Publishing Ltd.)

The quantum confinement effect and interesting optical properties of cesium lead halide (CsPbX 3 ; X = Cl, Br, I) perovskite quantum dots (QDs) and nanocrystals (NCs) have given a new horizon to lighting and photonic applications. Given the exponential rate at which scientific results on CsPbX 3 NCs are published in the last few years, it can be expected that the research in CsPbX 3 NCs will further receive increasing scientific interests in the near future and possibly lead to great commercial opportunities to realize these materials based practical applications. With the rapid progress in the single-photon emitting CsPbX 3 QDs and NCs, practical applications of the quantum technologies such as single-photon emitting light-emitting diode, quantum lasers, quantum computing might soon be possible. But to reach at cutting edge of stable perovskite QDs/NCs, the study of fundamental insight and theoretical aspects of crystal design is yet insufficient. Even more, it has aroused many unanswered questions related to the stability, optical and electronic properties of the CsPbX 3 QDs. Aim of the present review is to illustrate didactically a precise study of recent progress in the synthesis, properties and applications of CsPbX 3 QDs and NCs. Critical issues that currently restrict the applicability of these QDs will be identified and advanced methodologies currently in the developing queue, to overcome the roadblock, will be presented. And finally, the prospects for future directions will be provided., (© 2021 IOP Publishing Ltd.)

• Thermodynamic stability of CsPbX3 perovskite increases in the order CsPbI3, CsPbBr3, CsPbCl3. • Thermodynamic differences between the high and low temperature phases decreases in the order CsPbI3, CsPbBr3 and CsPbCl3. • CsPbI3 perovskite is barely stable under ambient conditions, and thus may not be suitable for long term applications. Inorganic cesium lead halide (CsPbX 3 , X = I, Br, Cl) perovskites have sparked broad interest for photovoltaic applications, which, however, may be plagued by chemical and thermodynamic instabilities. This work reports calorimetric studies on the formation enthalpies of CsPbX 3 perovskites, confirming decreasing thermodynamic stability in the order CsPbCl 3 , CsPbBr 3 and CsPbI 3. Cesium lead iodide (CsPbI 3), one of the most studied inorganic lead halide perovskites, is shown to be only barely stable from a thermodynamic perspective. This order of increasing instability is consistent with the variation of Goldschmidt tolerance factor. The perovskites are high temperature entropy-stabilized phases with respect to low temperature polymorphs, with the thermodynamics of phase transitions reflecting the above thermodynamic trends. [ABSTRACT FROM AUTHOR]

Perovskite nanostructures have attracted much attention in recent years due to their suitability for a variety of applications such as photovoltaics, light-emitting diodes (LEDs), nanometer-size lasing, and more. These uses rely on the conductive properties of these nanostructures. However, electrical characterization of individual, thin perovskite nanowires has not yet been reported. Here, conductive atomic force microscopy characterization of individual cesium lead halide nanowires is presented. Clear differences are observed in the conductivity of nanowires containing only bromide and nanowires containing a mixture of bromide and iodide. The differences are attributed to a higher density of crystalline defects, deeper trap states, and higher inherent conductivity for nanowires with mixed bromide-iodide content., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

All inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) perovskite nanocrystals (PNCs) exhibit promising applications in light-emitting devices due to their excellent photophysical properties. Herein, we developed a low-cost and convenient method for the preparation of CsPbX3 PNCs in a multiligand-assisted reaction system where peanut oil is applied as a ligand source. The mixed-halide PNCs with tunable optical-band gap were prepared by mixing the single-halide perovskite solutions at room temperature. The resulting PNCs had good monodispersity, with dimensions of 8–10 nm, high photoluminescence quantum yield (96.9%), narrow emission widths (15–34 nm), and tunable emission wavelength (408–694 nm), covering the entire visible spectrum. Additionally, various morphologies of PNCs, such as nanospheres, nanocubes, and nanowires, were obtained by controlling reaction temperature and time, and the amount of oleamine with multiple ligands in peanut oil potentially playing a dominant role in the nucleation/growth processes of our PNCs. Finally, the resulting CsPbBr3 PNCs were employed to develop a white light-emitting diode (WLED), demonstrating the potential lighting applications for our method. [ABSTRACT FROM AUTHOR]

Recently, lead halide-based perovskites have become one of the hottest topics in photovoltaic research because of their excellent optoelectronic properties. Among them, organic-inorganic hybrid perovskite solar cells (PSCs) have made very rapid progress with their power conversion efficiency (PCE) now at 23.7 %. However, the intrinsically unstable nature of these materials, particularly to moisture and heat, may be a problem for their long-term stability. Replacing the fragile organic group with more robust inorganic Cs + cations forms the cesium lead halide system (CsPbX 3 , X is halide) as all-inorganic perovskites which are much more thermally stable and often more stable to other factors. From the first report in 2015 to now, the PCE of CsPbX 3 -based PSCs has abruptly increased from 2.9 % to 17.1 % with much enhanced stability. In this Review, we summarize the field up to now, propose solutions in terms of development bottlenecks, and attempt to boost further research in CsPbX 3 PSCs., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

High-performance and hysteresis-less mesoscopic CsPbI 2 Br perovskite solar cells (PSCs) are demonstrated by adapting hole-transporting materials (HTMs) with controlled highest occupied molecular orbital (HOMO) values. The used model HTMs are poly-3-hexylthiophene (P3HT), poly-triarylamine (P-TAA), poly-fluoren-8-triarylamine (PF8-TAA), and poly-indenofluoren-8-triarylamine (PIF8-TAA), and their HOMO energy levels position to -4.98, -5.09, -5.45, and -5.52 eV, respectively. By controlling the HOMO of the HTMs, the average open-circuit voltages of 25 mesoscopic CsPbI 2 Br PSCs are controllable from 1.11 ± 0.030 V for a P3HT HTM-based device to 1.17 ± 0.023, 1.21 ± 0.027, and 1.27 ± 0.028 V for P-TAA, PF8-TAA, and PIF8-TAA HTM-based devices. As a result, the PIF8-TAA HTM-based mesoscopic PSC exhibits the highest open-circuit voltage of 1.31 V and power conversion efficiency (PCE) of 14.20% for the forward scan condition and 14.86% for the reverse scan condition under 1 sun illumination (100 mW/cm 2 AM 1.5G). In addition, the unencapsulated mesoscopic CsPbI 2 Br PSCs exhibited 10-14% of PCE degradation compared to their initial efficiency in maximum power point tracking under continuous 1 sun light soaking at 85 °C for 1000 h.

Recently, inorganic perovskite CsPbI 2 Br has gained much attention for photovoltaic applications owing to its excellent thermal stability. However, low device performance and high open-voltage loss, which are the result of its intrinsic trap states, are hindering its progress. Herein, planar CsPbI 2 Br solar cells with enhanced performance and stability were demonstrated by incorporating rubidium (Rb) cations. The Rb-doped CsPbI 2 Br film exhibited excellent crystallinity, pinhole-free surface morphology, and enhanced optical absorbance. By using low-cost carbon electrodes to replace the organic hole-transportation layer and metal electrode, an excellent efficiency of 12 % was achieved with a stabilized efficiency of over 11 % owing to the suppressed trap states and recombination in the CsPbI 2 Br film. Additionally, the annealing temperature for the Rb-doped CsPbI 2 Br film could be as low as 150 °C with a comparable high efficiency over 11 %, which is one of the best efficiencies reported for hole-transporting-layer-free all-inorganic perovskite solar cells. These results could provide new opportunities for high-performance and stable inorganic CsPbI 2 Br solar cells by employing A-site cation substitution., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)