Cs4 PbBr6 Research Articles

Pb-N Chemically Anchors CsPbBr3 on 1D Porous Tubular g-C3N4 for Enhanced Photocatalytic CO2 Reduction.

Halide perovskite CsPbBr3 (CPB) quantum dots (QDs) are considered as a promising candidate for solar-driven CO2 conversion for their unique optoelectronic properties and suitable band structure. However, the CO2 conversion efficiency of pristine CsPbBr3 quantum dots is severely limited due to their rapid electron-hole pair recombination and insufficient active sites. In this study, by immobilizing CPB QDs onto one-dimensional (1D) porous tubular g-C3N4 (TCN), an effective 0D/1D CPB@TCN heterojunction photocatalyst for CO2 reduction is fabricated. Density functional theory (DFT) calculations combined with experimental studies demonstrate that CPB QDs are uniformly anchored on the surface of TCN through Pb-N chemical bonding, resulting in efficient separation and transfer of photogenerated carriers in CPB@TCN photocatalysts. The resultant CPB@TCN photocatalysts exhibit significantly enhanced photocatalytic activity for CO2 reduction with the highest conversion rate of 22.62 μmol·g-1·h-1, which is 5.33-times higher than that of pristine CPB QDs. This work unveils the interfacial bonding mechanism of CPB@TCN heterojunction through Pb-N chemical bond, which provides new insights for the development perovskite-based heterojunction photocatalysts.

Aqueous‐Phase Preparation of Core–Shell Perovskite Nanorods Encapsulated in Polydopamine with Ultrahigh Water Stability

All‐inorganic perovskite CsPbBr3 (CPB) nanocrystals (NCs) are not widely applied in aqueous environments due to their readily decomposable nature. Therefore, the aqueous‐phase preparation of CPB NCs has been a considerable challenge. In this work, a feasible method is proposed for preparing aqueous‐phase core–shell CPB nanorods (NRs) encapsulated with polydopamine (PDA) by employing a multifunctional additive cesium trifluoroacetate (Cs‐TFA). Highly luminescent TFA‐CPB NRs are obtained via a chemical transformation of Cs4PbBr6 NCs in water. Subsequently, PDA constitutes a robust shell on the surface of TFA‐CPB NRs through the covalent oxidative polymerization, which effectively reduces the original dynamic properties of surface ligands, retards the decomposition of ligands and inhibits the leakage of Pb2+ ions. The results demonstrate that the fluorescence intensity of TFA‐CPB@PDA NRs maintains 49.3% of the initial intensity after 136 days. Meanwhile, the NRs exhibit low cytotoxicity, and the cell viability remains at 80% when the concentration of the NRs is 200 μg mL−1. The reliable preparation of aqueous‐phase core–shell perovskite NRs (PNRs) will facilitate their development in many fields, such as materials science, biology, medicine, and their applications in aqueous environments.

Transferrable CsPbBr3 Perovskite Single-Crystalline Films for Visible-Wavelength Photodetectors.

In this study, we propose large-scale CsPbBr3 (CPB) single-crystalline films (SCFs) grown by a one-step vapor-phase epitaxy (VPE) method for application in optoelectronic devices. After optimizing the transport speed of the precursor and cooling rate, we obtained continuous CPB films with a lateral size exceeding 2 cm2, and the thickness could be controlled from several micrometers to hundreds of nanometers. Crystallography and optoelectronic characterization proved the excellent crystallinity and very low trap density (2.14 × 1011) of the SCFs. Furthermore, we demonstrate a transfer-assembly strategy for fabricating perovskite SCF-based heterostructures for visible photodetectors. The high-quality SCF films in the active layer suppress the leakage current, leading to a low dark current of 5 × 10-10 A at -0.6 V. Therefore, the self-biased photodetector based on the vertical CsPbBr3 SCF-SnO2 heterostructure showed a high responsivity of 1.9 A/W, a detectivity of 4.65 × 1012 Jones, and a large on/off ratio of 4.63 × 103 under a 1 mW/cm2 450 nm light illumination. Our study not only demonstrates the excellent performance of single-crystalline perovskite-based photodiodes but also provides a universal assembly method for the integration of monocrystalline perovskite films in optoelectronic devices.

Harnessing Pb-S Interactions for Long-Term Water Stability in Cesium Lead Halide Perovskite Nanocrystals.

Lead halide perovskite nanocrystals (LHP NCs) have garnered attention as promising light-harvesting materials for optoelectronics and photovoltaic devices, attributed to their impressive optoelectronic properties. However, their susceptibility to moisture-induced degradation has hindered their practical applications. Despite various encapsulation strategies, challenges persist in maintaining their stability and optoelectronic performance simultaneously. Here, a ligand exchange approach is proposed using (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide (MUTAB) to enhance the stability and dispersibility of CsPbBr3 (CPB) NCs in aqueous environments. MUTAB enables effective surface passivation of the CPB NCs via robust Pb-S interactions at the S-terminal while concurrently directing water molecules through the unbound cationic N-terminal or vice versa, ensuring water dispersibility and stability. Spectroscopic analysis confirms retained structural and optical integrity post-ligand exchange. Crucially, MUTAB-bound CPB NCs exhibit sustained charge transfer properties, demonstrated by aqueous colloidal oxidation reactions. This ligand exchange strategy offers a promising pathway for advancing LHP NCs toward practical optoelectronic and photocatalytic applications.

In situ preparation of water-stable SiO2@mSiO2/CsPbBr3 and its application in WLED

Recently, all-inorganic perovskites as photoluminescent materials have attracted significant attention in the field of light-emitting diodes. However, their instability towards UV light, high temperature, and water has impeded widespread commercial applications. We propose a facile strategy for synthesizing CSSM-CPB by encapsulating perovskite CsPbBr3 (CPB) into the channels of core-shell silica microspheres (CSSM). Subsequently, the channels of CSSM-CPB were sealed with octadecyltrichlorosilane (ODS). Consequently, the stability of CSSM-CPB to UV light, high temperature, and water significantly improved. Notably, CSSM-CPB retains a high fluorescence emission intensity even after immersion in water for 30 days. Furthermore, the photoluminescence quantum yield of CSSM-CPB reaches 68%, compared to just 30% for discrete CPB. A CSSM-CPB-WLED was also developed, exhibiting a color temperature (Tc) of 5869 K, Commission Internationale de l′Éclairage (CIE) color coordinates of (0.34, 0.34), a luminous efficiency of 86.31 lm W−1, and a color gamut overlap with the NTSC space of approximately 121.1%. These results indicate a significant enhancement over CPB-WLED, suggesting that the stability of CPB can be improved through silica encapsulation and hydrophobic material sealing. This approach has potential for commercial application in display devices requiring high stability.

Boosting exciton dissociation and charge transfer in CsPbBr3 QDs via ferrocene derivative ligation for CO2 photoreduction

Photo-catalytic CO2 reduction with perovskite quantum dots (QDs) shows potential for solar energy storage, but it encounters challenges due to the intricate multi-electron photoreduction processes and thermodynamic and kinetic obstacles associated with them. This study aimed to improve photo-catalytic performance by addressing surface barriers and utilizing multiple-exciton generation in perovskite QDs. A facile surface engineering method was employed, involving the grafting of ferrocene carboxylic acid (FCA) onto CsPbBr3 (CPB) QDs, to overcome limitations arising from restricted multiple-exciton dissociation and inefficient charge transfer dynamics. Kelvin Probe Force Microscopy and XPS spectral confirmed successfully creating an FCA-modulated microelectric field through the Cs active site, thus facilitating electron transfer, disrupting surface barrier energy, and promoting multi-exciton dissociations. Transient absorption spectroscopy showed enhanced charge transfer and reduced energy barriers, resulting in an impressive CO2-to-CO conversion rate of 132.8 μmol g-1 h-1 with 96.5% selectivity. The CPB-FCA catalyst exhibited four-cycle reusability and 72 h of long-term stability, marking a significant nine-fold improvement compared to pristine CPB (14.4 μmol g-1 h-1). These results provide insights into the influential role of FCA in regulating intramolecular charge transfer, enhancing multi-exciton dissociation, and improving CO2 photoreduction on CPB QDs. Furthermore, these findings offer valuable knowledge for controlling quantum-confined exciton dissociation to enhance CO2 photocatalysis.

Obtaining Ligand-Free Aqueous Au-Nanoparticles Using Reversible CsPbBr3 ↔ Au@CsPbBr3 Nanocrystal Transformation.

Water-hexane interfacial preparation of photostable Au@CsPbBr3 (Au@CPB) hybrid nanocrystals (NCs) from pure CsPbBr3 (CPB) NCs is reported, with the coexistence of exciton and localized surface plasmon resonance with equal dominance. This enables strong exciton-plasmon coupling in these plasmonic perovskite NCs where not only the photoluminescence is quenched intrinsically due to ultrafast charge separation, but also the light absorption property increases significantly, covering the entire visible region. Using a controlled interfacial strategy, a reversible chemical transformation between CPB and Au@CPB NCs is shown, with the simultaneous eruption of larger-size ligand-free aqueous Au nanoparticles (NPs). An adsorption-desorption mechanism is proposed for the reversible transformation, while the overgrowth reaction of the Au NPs passes through the Au aggregation intermediate. This study further shows that the plasmonic Au@CPB hybrid NCs as well as ligand-free Au NPs exhibit clear surface enhanced Raman scattering (SERS) effect of a commercially available probe molecule. Overall, the beautiful interfacial chemistry delivers two independent plasmonic materials, i.e., Au@CPB NCs and ligand-free aqueous Au NPs, which may find important implications in photocatalytic and biomedical applications.

Defect Engineering of Metal Halide Perovskite Nanocrystals via Spontaneous Diffusion of Ag Nanocrystals.

Perovskite nanocrystals (NCs) have emerged as a promising building block for the fabrication of optic-/optoelectronic-/electronic devices owing to their superior characteristics, such as high absorption coefficient, rapid ion mobilities, and tunable energy levels. However, their low structural stability and poor surface passivation have restricted their application to next-generation devices. Herein, a drug delivery system (DDS)-inspired post-treatment strategy is reported for improving their structural stability by doping of Ag into CsPbBr3 (CPB) perovskite NCs; delivery to damaged sites can promote their structural recovery slowly and uniformly, averting the permanent loss of their intrinsic characteristics. Ag NCs are designed through surface-chemistry tuning and structural engineering to enable their circulation in CPB NC dispersions, followed by their delivery to the CPB NC surface, defect-site recovery, and defect prevention. The perovskite-structure healing process through the DDS-type process (with Ag NCs as the drug) is analyzed by a combination of theoretical calculations (with density functional theory) and experimental analyses. The proposed DDS-inspired healing strategy significantly enhances the optical properties and stability of perovskite NCs, enabling the fabrication of white light-emitting diodes.

Inducing superior discharged energy density of the nanocomposite films with CsPbBr3 in-situ dispersed in ferroelectric polymer

Polymer-based capacitors are regarded as paramount components in advanced electrical systems due to their intrinsically superior breakdown strength (Eb) and excellent processability. Although the enhancement of dielectric constant (εr) of polymer-based composites has been realized by loading high‐εr inorganic fillers, this approach confronts considerable challenges in filler agglomeration. In this research, CsPbBr3 (CPB) nanoparticles are via in-situ in ferroelectric polymers [P(VDF-HFP)] to form high-quality nanocomposites. εr and Eb of the nanocomposites are concomitant enhancement via introduction of only 0.1 wt.% CPB, leading to an ultrahigh Ud ∼ 24.1 J cm-3 at 705 MV m-1 with superior efficiency (η) of 64 % and stability up to 2.5 × 104 charge-discharge cycles. COMSOL Multiphysics simulations further demonstrate that the in-situ prepared composites are conducive to inhibiting the growth of electronic trees caused by inhomogeneous electric field distribution. This contribution extends the synthesis method to prepare perovskites-polymer dielectrics and provides a novel strategy for fabricating high-performance polymer-based composite capacitors.

An innovative strategy: ultra-stable alkaline earth modified CsPbBr3 quantum dots glass was prepared by washing-heat cycle for high definition backlight display

All-inorganic perovskite quantum dots (QDs) as high-quality materials for backlight display are still limited by their own low stability. Herein, the crystallization of CsPbBr3 (CPB) QDs in a glass matrix was promoted by modifying the glass network structure with alkaline earth metals (Mg, Ca, Sr, Ba). What's more, a washing-heat treatment cycle strategy was used to optimize the best-modified sample (CPB–Mg). Among them, CPB-12Mg (add 12% MgO) showed a high photoluminescence quantum yield (PLQY = 62%) after the cycling process. More surprisingly, the six-step washing-heat treated-sample (CPB–12Mg-6) showed excellent stability. When CPB-12Mg-6 was irradiated for 240 h at 60°C, 90% relative humidity (RH), and 880 W/m2 blue light power (60°C, 90% RH, 880 W/m2), the original 90% fluorescence emission could still be maintained. Subsequently, a series of CPB-12Mg-6/CsPbBr1.5I1.5@PS light conversion films were prepared by the master batch blending method. The backlight conversion film for liquid crystal display (LCD) achieves a wide color gamut that covers 126% of the NTSC 1953 and 93.6% of the Rec.2020 standard. This innovative washing-heat treatment cycle strategy provides a new idea for improving the stability of perovskite quantum dots.

Anchoring Cs4PbBr6 Crystals to PbSe Nanocrystals for the Fabrication of UV/VIS/NIR Photodetectors Using Halide Surface Chemistry

AbstractNanocrystal (NC)‐in‐matrix solids are currently attracting considerable research attention in the fields of materials science and engineering owing to their unique optoelectronic characteristics and high stability. However, the interaction between the NC surface and the matrix has been veiled and induces interface defect states that degrade the performance of photovoltaics. In this study, the effect of halide ligands on the formation of a Cs4PbBr6 (CPB) crystal matrix by determining the surfaces of PbSe NCs is investigated. The surface of the PbSe NCs is passivated with halide ions (Cl−, Br−, or I−), and the CPB crystal matrix is formed via PbBr2/CsBr treatment onto the PbSe NCs. The effects of different halide ions on the nucleation/growth of the CPB matrix are examined by chemical, structural, and optical analyses. It is found that each halide ligand has a distinct effect not only on the anchoring of CPB but also on its carrier transport mechanisms. To characterize the electronic properties of the NC matrix, its carrier mobility, photoresponsivity, and stability are measured using field‐effect transistors. Consequently, it is demonstrated that more densely passivated PbSe NCs form a higher‐quality CPB matrix. Using a NC matrix, ultraviolet‐/visible‐/near‐infrared‐active flexible photodetectors are achieved.

Cesium Lead Bromide Nanocrystals: Synthesis, Modification, and Application to O2 Sensing.

The fluorescence intensity of inorganic CsPbBr3 (CPB) perovskite nanocrystals (NCs) decreases in the presence of O2. In this study, we synthesized CPB NCs with various shapes and sizes for use as optical gas sensing materials. We fabricated O2 gas sensors from the various CPB NCs on several porous and nonporous substrates and examined the effects of the NC shapes and aggregate sizes and the substrate pore size on the device response. Our sensor fabricated from CPB nanocrystals on a porous substrate exhibited the highest response; the porous substrate allowed the rapid diffusion of O2 such that the NC surface was exposed effectively to the gas. Thus, the interfacial interaction between NC surfaces and substrates is a critical factor for consideration when preparing gas sensors with a high response.

Compression packing of CsPbBr3 perovskite quantum dots with boron nitride nanosheets for enhanced stability: A nano-encapsulation strategy

All-inorganic CsPbX3 (X = Cl, Br, I) perovskite quantum dots (QDs) are vulnerable to adverse factors such as light, high temperature and moisture due to its inherent structural instability, thus limiting its application in the field of optoelectronics. Here, we propose a nano-encapsulation strategy to improve the stability of CsPbBr3 (CPB) QDs via compression packing of the QDs within two-dimensional flexible BN nanosheets (BNNS). After pre-preparing of CPB/BNNS nanocomposite powder, a dense CPB/BNNS plate is obtained through the compression packing of the powder under the action of external force in a certain mold. By further grinding and sieving, powdery CPB/BNNS particles with the same encapsulation effect are obtained. As compared with CPB/BNNS nanocomposite powder, the plate and particle samples after compression packing can retain the excellent photoluminescence (PL) properties of CPB QDs, while showing greatly improved stabilites in various adverse environments. After compression packing, both of the CPB QDs anchored in BNNS folds and exposed to BNNS interlayers can be well encapsulated in the dense composite structure, which can realizing the successful nano-encapsulation of CPB QDs by BNNS. In addition, the white LED device constructed with CPB/BNNS particle as green phosphor exhibits excellent white light emission and stability.

Retarded Charge Recombination to Enhance Photocatalytic Performance for Water-Free CO2 Reduction Using Perovskite Nanocrystals as Photocatalysts.

Femtosecond transient absorption spectral (TAS) investigations were performed to understand the carrier relaxation mechanism for perovskite nanocrystals Cs1-xFAxPbBr3 (CF, x = 0.45) and CsPbBr3 (CS), which served as efficient photocatalysts for splitting of CO2 into CO and O2 in the absence of water. Upon light irradiation for 12 h, formation of deep trap states was found for both CS and CF samples with spectral characteristics of the TAS photobleach (PB) band showing a long spectral tail extending to the long wavelength region. The charge recombination rates at the shallow surface states, bulk states, and deep-trapped surface state were found to be significantly retarded for the CF sample than for the CS sample, in agreement with the photocatalytic performances for CO product yields of the CF catalyst being greater by a factor of 3 compared to those of the CS catalyst.

Vacuum-Vapor-Deposited 0D/3D All-Inorganic Perovskite Composite Films toward Low-Threshold Amplified Spontaneous Emission and Lasing.

Vacuum vapor deposition (VVD) is a promising way to advancing the commercialization of perovskite light sources owing to its convenience for wafer-scale mass production and compatibility with silicon photonics manufacturing infrastructure. However, the light emission performance of VVD-grown perovskites still lags far behind that of the conventional solution-processed counterparts due to their inferior luminescence properties. Here, a 0D/3D cesium-lead-bromide perovskite composite film is prepared on Si/SiO2 substrates through composition modulation with the VVD method, which exhibits an ultralow amplified spontaneous emission (ASE) threshold down to 14.3 µJ cm-2 in the optimal films, which is on par with that of the solution-processed counterparts. Meanwhile, they also display intriguing operational stability with negligible emission intensity decay under continuous excitation above ASE threshold for 4h in the air. The outstanding ASE performance mainly originates from the reduced trap density and weakened electron-phonon coupling in the 3D CsPbBr3 phase enabled by the incorporation of the 0D Cs4 PbBr6 phase. Finally, by integrating the composite film with the distributed feedback (DFB) cavity, DFB lasing is achieved with a low threshold of 18.2 µJ cm-2 under nanosecond-pulsed laser pumping, which highlights the potential of VVD-processed perovskites for developing high-performance lasers.

Perovskite-Nanoparticle-Incorporated NH2-MIL-125(Ti) Nanoreactors with an Optimal Conduction Band Offset for Visible-Light-Driven CO2 Reduction

To alleviate the intense global warming crisis, developing high-performance photocatalysts for CO2 reduction reaction (CO2RR) to green fuels is of great importance. CsPbBr3 (CPB) has been proved as a promising photocatalyst for CO2RR due to the excellent visible-light response and energetic reduction potential, but its practical performance is still deficient, suffering from severe carrier recombination and poor CO2 adsorption capability. Herein, we demonstrate novel CPB-nanocrystal-incorporated NH2-MIL-125(Ti) (NH2-MIL-125(Ti)/CPB) nanoreactors for solar-driven CO2RR. Attributed to the optimal conduction band offset (CBO) in the NH2-MIL-125(Ti)/CPB heterojunction, excellent carrier transfer is obtained with retained energetic photoreduction potential. Moreover, strong interfacial interaction is demonstrated, enabling the synergistic effect of promoted CO2 adsorption on NH2-MIL-125(Ti) and facilitating interfacial carrier injection. Therefore, greatly enhanced photocatalytic CO2RR performance is achieved by as-designed nanoreactors. This work offers a deep understanding into the synthesis of functionalized perovskite-based materials with rationally designed carrier transfer behaviors for not only photocatalytic reactions but also photovoltaic fields.

CsPbBr3 nanocrystals glass with finely adjustable wavelength and color coordinate by MgO modulation for wide-color-gamut backlight displays

All-inorganic perovskite CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) are becoming a critical material for the narrow-band fluorescent material in the field of backlit displays. Herein, CsPbBr3 (CPB) NCs glasses with finely adjustable wavelength were successfully prepared in the narrow range of 522–533 nm by controlling the content of MgO in borosilicate glass matrix. It is surprising that the addition of MgO enhances the optical properties of CPB NCs, as well as improves their stability. Furthermore, in order to verify its application in backlight display, the light conversion film with a color gamut of up to 129% of NTSC 1953 was successfully prepared, displaying more details of object color on the liquid crystal display (LCD) screen compared with commercial one. These results undoubtedly provide a broad road for wide color gamut backlight display with respect to perovskite nanomaterials.

Large red shift from blue to green in the photoluminescence of pure CsPbBr3 nanoplatelets triggered by the cooperative effect of ligands combination

With unique electronic and optical properties, the size and luminescence color of metal halide perovskite nanocrystals CsPbBr3 (CPB) are crucial for the potential applications including solid-state lighting, photovoltaics, and thermoelectrics. In this work, we have developed a viable design strategy toward cubic CPB nanoplatelet (NPs) with blue emission at 450–467 nm and a large red shift to the green region at 500–512 nm occurs through a cooperative effect of the ligands 4-bromo-butyric acid (BBA) and oleylamine (OLA). The influence of the molecular ratio of BBA/OLA, reaction time and temperature on the transformation from blue to green has been investigated systematically. The red shift in the PL of CPB NPs is ascribed to the growth of the crystals with decreased quantum confinement. The photoluminescence quantum yields (PLQYs) of the blue and green luminescence of the obtained CPB NPs reach 94.4 % and 84.4 %, respectively. This proposed strategy not only experimentally fabricates size-adjustable CPB NPs but also helps to reveal in depth the mechanisms of the large variation of quantum confinement in pure cubic CPB NPs.

In Situ Preparation of CsPbBr3 @CsPb2 Br5 Composite Assisted with Water as a Highly Efficient and Stable Catalyst for Photothermal CO2 Hydrogenation.

Lead halide perovskite has triggered a lot of research due to its superior optical properties. However, halide perovskite materials have poor environmental stabilities and are easily affected by external factors such as water and heat, resulting in structural decomposition and performance failure. Contrary to this commonplace concept, it is found that CsPbBr3 (CPB) can convert to CsPb2 Br5 (CP2B5) partially when meeting a small amount of water, and the CsPbBr3 @CsPb2 Br5 (CPB@CP2B5) composite is synthesized by an in situ method accordingly. The CPB@CP2B5 composite shows an enhanced catalytic performance compared with pure CPB, as well as a dramatically synergistic effect of photo and thermal for catalytic CO2 hydrogenation. The CO production rate of CPB@CP2B5 is determined as 69 μmol g-1 h-1 under light irradiation at 200 °C, which is 156.8 and 43.4 times higher than that under pure photo (0.44 μmol g-1 h -1 ) and pure thermal (1.59 μmol g-1 h -1 ) condition, respectively. Meanwhile, the CPB@CP2B5 sample is also stable, which shows no significant decline in the catalytic activity during 8 cycles of repeated experiments. The probable mechanism is explored by utilizing a series of in situ characterizations.

Metal element doping in Cs(Pb1 − xDEx)Br3 for solar cell materials

The structure, and the electronic properties, caused by alkaline earth metals and transition metals substituting for Pb in CsPbBr3 (CPB) are studied by the first principal calculations. Obtained results show that with increasing the dopants concentration, the substitution of Pb with alkali earth metals in CsPbBr3 induces an increase of the electronic band gap, and the direct band gap turns to be the indirect band gap; On the other hand, the substitution of Pb by transition metal elements in CsPbBr3 induces a decrease of the band gap, and the band gap becomes indirect band gap. Doping for Pb may adjust the bandgap of the CsPbBr3 to be 1.3∼1.5eV for fabricating the high efficiency solar cells. The calculated results also prove that the electronegativity of the metal is related the band gap of the doped CPB, which may be related to the outermost s-orbital electrons in the band. The average energy of the s-orbital electrons of the doped metal is highly consistent with the electronegativity of the metal and the change of the band gap after doping. This may open a new way to design the dopants for CPB.