Pb Precursor Research Articles

Mn derived growth of CsPbBr3 nanoplatelets for stable and bright orange emission

Abstract Mn-doped perovskites have been extensively studied in optics, magnetism, and electronics due to their orange emission. However, successful Mn doping required a high Mn/Pb feed ratio. In this paper, Mn-doped CsPbBr3 nanoplatelets (NPLs) with bright orange emission were prepared by a two-step slow thermal injection synthesis. The slow injection of precursors effectively slow-down the crystal growth kinetic process and controls the growth of undoped CsPbBr3 NPLs. This process also significantly improves Mn doping efficiency. Mn doping induced the generation of numerous precursor clusters during the growth of CsPbBr3 NPLs, and the formation of these clusters was crucial for enhancing the doping efficiency. The maximum amount of Mn precursor in CsPb0.83Mn0.17Br3 was 50% of Pb precursors. The photoluminescence quantum yields (PLQYs) of CsPb0.94Mn0.06Br3 NPLs reached up to 80.6%, which was 3.1 times of that of CsPbBr3 NPLs. The PL properties of Mn-doped CsPbBr3 NPLs were significantly enhanced compared with pure CsPbBr3 NPLs. The growth process and luminescence mechanism of Mn-doped CsPbBr3 NPLs were discussed. High PLQYs and efficient Mn doping supplied an ideal approach for the preparation of various CsPbX3 (X = Cl, Br, and I) NCs for commercial applications.

Nanostructured PbSe Films Deposited by Spray Pyrolysis Using PbSe Colloidal Solutions.

This work describes the spray pyrolysis deposition of PbSe films, using as-prepared PbSe colloids as the starting solution. The PbSe colloids were prepared by using the alkahest approach, where Pb and Se precursors were made to react with the following green polyols: glycerin, ethylene glycol, and propylene glycol, to subsequently spray them onto glass substrates. The results of the characterization indicated that amine or thiol groups-free and single-phase rock-salt cubic PbSe powder was obtained, producing nanocrystals 16-30 nm in size. X-ray diffraction also showed that the PbSe films containing PbSeO3 and PbO·xH2O as impurity phases were produced during the deposition. The morphology of the powders and films was developed by a self-assembly process, in which the primary PbSe nanoparticles self-assemble to produce peanut-like microstructures. Additionally, a non-continuous and porous feature was formed in the thick films. Certain films revealed optical structures characterized by broad- and low-intensity bands resembling an exciton-like behavior. This could be attributed to the presence of nanocrystals with a size less than the Bohr radius, indicating reminiscent quantum effects. The results suggest that the usage of colloidal dispersions as spray solutions represents an effective approach to forming PbSe films, as well as that the synthesis method allows for the elimination of thiol and amine groups before deposition, significantly simplifying the process.

Tailoring Molecular Dimensions of Cesium Lead Bromide Perovskites with Varying Compositions of Oleic Acid and Oleylamine

AbstractThe evidence on deciphering nucleation and growth of cesium lead halide perovskite crystals, and establishing the phase diagram of cesium lead halide perovskites of different dimensions is still lacking. In this work, a facile method for the synthesis of cesium lead bromide crystals of different molecular level dimensions at room temperature is presented by varying the OA/OAm ratios without changing the proportions of Cs and Pb precursors. Bromide ions are gradually released in the systems through the gamma‐ray radiation chemistry of bromobenzene. As the volume ratios of OA/OAm increase, different products such as CsBr, Cs4PbBr6 (0D), white δ‐CsPbBr3 (1D), γ‐CsPbBr3 (3D) associated with PbBr2 sheets, and γ‐CsPbBr3 are obtained in order. 1D δ‐CsPbBr3 can be transformed into 2D CsPb2Br5 through CsBr stripping in water. The phase diagram established in this work is helpful for understanding the nucleation and growth mechanism of Cs–Pb–Br perovskite crystals of different dimensions. The nucleation of Cs–Pb–Br perovskite crystals is driven by the supersaturation of either CsBr or PbBr2 caused by varying OA/OAm ratios, i.e., 0D Cs4PbBr6 at the supersaturation of CsBr, while 3D γ‐CsPbBr3 at the supersaturation of PbBr2. 1D perovskite is the intermediate state between 0D and 3D perovskites.

A Demulsification-Crystallization Model for High-Quality Perovskite Nanocrystals.

A room-temperature technique with all-nonpolar-solvent, which circumvents the sensitivity of ionic perovskite to polar solvent, has become attractive for the synthesis of metal halide perovskite nanocrystals (PNCs). However, the lack of understanding of the inner mechanism, especially for the state of the precursor and the crystallization process of the PNCs, hinders further development of this technique. Here, through systematic study of the Pb precursor and in situ characterization of the PNCs, it is revealed that the reverse micelle nature of the Pb precursor exactly creates a novel demulsification-crystallization (D-C) model, namely, a two-stage nucleation is divided by a demulsification process for the PNCs. On this basis, a top efficiency for green light-emitting diodes based on PNCs is obtained with a maximum external quantum efficiency of 22.5% through tailoring the D-C model using a multiple-acid-anion synergistic assisted strategy to obtain high-quality PNCs. Beyond the high efficiency, the work paves the way for diverse ideas in PNC synthesis.

Near-Infrared Emission of HgTe Nanoplatelets Tuned by Pb-Doping.

Doping the semiconductor nanocrystals is one of the most effective ways to obtain unique materials suitable for high-performance next-generation optoelectronic devices. In this study, we demonstrate a novel nanomaterial for the near-infrared spectral region. To do this, we developed a partial cation exchange reaction on the HgTe nanoplatelets, substituting Hg cations with Pb cations. Under the optimized reaction conditions and Pb precursor ratio, a photoluminescence band shifts to ~1100 nm with a quantum yield of 22%. Based on steady-state and transient optical spectroscopies, we suggest a model of photoexcitation relaxation in the HgTe:Pb nanoplatelets. We also demonstrate that the thin films of doped nanoplatelets possess superior electric properties compared to their pristine counterparts. These findings show that Pb-doped HgTe nanoplatelets are new perspective material for application in both light-emitting and light-detection devices operating in the near-infrared spectral region.

PbOx phase separation in PbZr0.52Ti0.48O3 based capacitors made using sol-gel films with high Pb precursor excess

We present a study of the impact of Pb excess content on electrical performance of lead zirconate titanate (PbZr0.52Ti0.48O3, PZT) thin-film capacitors. High Pb excess eliminates the ZrOx interface layer between the PZT and the electrode but also reduces the breakdown field, while the linear dielectric character of the capacitor response increases with Pb excess. The chemical sensitivity of hard x-ray photoelectron spectroscopy with in situ bias provides direct evidence of a polar but the non-ferroelectric PbOx phase in the bulk of the sol-gel film. The phase has a distinct core level signature and is consistent with the dielectric response at low field, which becomes more ferroelectric at higher field, as well as the lower remanent polarization and breakdown field.

Direct deposition of lead sulfide nano-optoelectronic films on polymer substrate

Nanocrystals have exhibited unique optoelectronic properties and demonstrated a wide range of applications in light-emitting devices, semiconductor devices and solar cell devices. However, previous studies usually deposit nanocrystal films on traditional rigid substrates, limiting their applications in large-scale, direct-deposited flexible device fabrication processes, such as roll-to-roll printing process. Here, we report a direct deposition method for lead sulfide (PbS) nanocrystal films on flexible polymer substrates. By adding triethanolamine-coordinated Pb precursors to the reaction system to enhance the adhesion to the substrate and controlling the precursor ratios, we obtained high-quality flexible PbS films. The film is composed of octahedral PbS nanocrystals with preferred (111) orientation. The optical band gap of the nanocrystal films can be tuned from 1.32 eV to 1.60 eV by adjusting the ratio of the precursors, and an ideal band gap of 1.4 eV for single-junction solar cells was also obtained when Pb to S ratio reaches 1.4:1. More importantly, the flexible PbS films exhibit high charge carrier mobility of up to 25 cm2 V[Formula: see text] s[Formula: see text], which is comparable to that of PbS films grown on traditional rigid substrates (e.g. silicon wafers or glasses). To our knowledge, this mobility is also the highest for PbS fabricated directly on flexible substrates. Our study provides a new approach for the preparation of low-cost and roll-to-roll processable nanocrystal films for future flexible optoelectronic devices.

PbS nanocrystals decorated Reduced Graphene Oxide for NIR responsive capacitive cathodes

Novel hybrid nanocomposites formed of 1-Pyrene Carboxylic Acid (PCA) functionalized Reduced Graphene Oxide (RGO) sheets, surface decorated with UV–Vis–NIR light-harvester PbS nanocrystals (NCs), are prepared by means of an in situ colloidal chemistry approach, using oleic acid (OLEA) as a surfactant. PCA molecules anchored onto the RGO sheets feature carboxyl groups that serve as coordinating sites for the PbS NCs heteronucleation. Here, the mechanism underlying the NCs decoration of RGO is investigated and the interplay between the concentration of PCA and OLEA and the Pb precursor:OLEA molar ratio are demonstrated able to careful control NCs morphology and size distribution, governing also RGO covering density. Remarkably, PCA-RGO/PbS NCs modified Indium Thin Oxide (ITO) electrodes show an electrochemical specific capacitance much higher than that characterizing the single components of the nanocomposite, that can be further enhanced under illumination in the NIR. The nanocomposite modified electrodes demonstrate to behave as (photo)electrochemical supercapacitors, chemically stable, able to work both as (photo)charging and blocking electrodes, exhibiting a photocathodic behavior. The investigation of the NIR-light enhanced photocapacitive characteristics of the hybrid (photo)cathodes provides useful insights on their future integration in devices, including electrochemical photocapacitors and photoelectrochemical (bio)sensors.

Role of precursor concentrations on the formation of ternary Pb1−xSrxSe QDs in silicate glasses

Lead selenide quantum dots (QDs) were precipitated in silicate glasses with different contents of SrO. As the concentration of SrO increased from 0 to 10 mol%, the absorption peaks of the glasses with the heat treatment at 520 °C for 10 h blue-shifted from 1535 nm to 947 nm, and their photoluminescence (PL) peaks from 1578 nm to 1184 nm. The blue-shifts resulted from the incorporation of Sr2+ ions into PbSe crystal lattice, which leads to the increase of the bandgap of PbSe QDs. Meanwhile, the optical properties of Sr2+-doped PbSe QDs were investigated by changing the precursor concentrations of Pb and Se. It is found that the concentration of Sr2+-doped PbSe QDs in the glassy matrix is mainly determined by the contents of the Pb precursor. To form larger size QDs requires higher oversaturation of Se to Pb elements, which promoted the further growth of QDs.

Designed sol-gel precursors for atomically dispersed Nb and Pb within TiO2 as catalysts for dihydroxyacetone transformation.

The 'bottom-up' synthesis of homogeneously doped metal oxide nanoparticles (NPs) with precision at the atomic/molecular level offers many advantages. We report here the synthesis, structural characterization and hydrolytic behavior of new N-methyldiethanolamine-modified precursors of Ti(iv), Nb(v) and Pb(ii) and their application as excellent sol-gel precursors for obtaining atomically dispersed Nb and Pb within TiO2 having high surface areas (253-355 m2 g-1) and tunable acidic properties. Preliminary results on the use of these doped TiO2 as water-tolerant catalysts in transforming dihydroxyacetone to lactic acid are presented.

Fabrication of single phase CsPbBr3 films via in situ metal reaction

We developed an in situ metal reaction strategy to fabricate single phase CsPbBr3 films by reacting Pb precursors with a mixture of CsBr and HBr. The purity of the CsPbBr3 film can be controlled by tuning the thickness of sputtered Pb.

Growth of thin film ferroelectric PZT, PHT, and antiferroelectric PHO from atomic layer deposition precursors

AbstractWe present a conformal method of growing ferroelectric lead hafnate‐titanate (PbHfxTi1−xO3, PHT) and lead zirconate‐titanate (PbZrxTi1−xO3, PZT) using atomic layer deposition (ALD) precursors. The 4+ cation precursors consist of tetrakis dimethylamino titanium (TDMAT), tetrakis dimethylamino zirconium (TDMAZ) and tetrakis dimethyl amino hafnium (TDMAH) for Ti, Zr, and Hf, respectively. The Pb (2+) precursor was Lead bis(3‐N,N‐dimethyl‐2‐methyl‐2‐propanoxide) [Pb(DMAMP)2]. PZT was limited to lead titanate (PTO)‐rich compositions, where x <0.25 for PbZrxTi1−xO3, and exhibited a remnant polarization of 26‐27 µC/cm2 with a coercive field between 150 and 170 kV/cm. The 3D‐structure coating capability of PZT was demonstrated by deposition on micromachined trench sidewalls 45 µm deep. We fabricated Microelectromechanical systems (MEMS) cantilever arrays with PZT thin films grown using the present method and demonstrated piezoelectric actuation. Alternatively, PHT was deposited with Ti and Hf compositions within ±1 at.% of the morphotropic phase boundary (MPB). The PHT exhibited a remanent polarization of 7.0‐8.7 µC/cm2 with a coercive field between 84‐100 kV/cm. We applied the same Pb and Hf precursors from the PHT process to grow antiferroelectric lead‐hafnate (PHO), which showed the characteristic electric field‐induced ferroelectric phase transition at approximately ±280 kV/cm and a maximum polarization of approximately ±32.8 µC/cm2.

Enhanced Device Performances of MAFACsPb(IxBr1-x) Perovskite Solar Cells with Dual-Functional 2-Chloroethyl Acrylate Additives.

Perovskite photovoltaics (PePVs) tend to suffer from a high density of defects that restrict the device in terms of performances and stability. Therefore, defect passivation and film-quality improvement of perovskite active layers are crucial for high-performance PePVs. In this work, 2-chloroethyl acrylate (CEA) with C═O and -Cl groups in Cs0.175FA0.750MA0.075Pb (I0.880Br0.120) precursor solutions is introduced as a novel bifunctional additive to act as both a defect passivator and perovskite-growth controller. With the aid of CEA, the perovskite crystallinity and average grain size are improved, and perovskite defects are effectively reduced, thus increasing the representative efficiency (PCE = 19.32%). PePVs with CEA also maintain their initial efficiency of 85% even after about 500 h under air conditions with a humidity of 40 ± 5%. As a result, this study proves that the novel additive CEA can produce higher PePV efficiency and more stable devices.

The Instability of Monolayer-Thick PbSe on VSe2

Two-dimensional monolayers derived from 3D bulk structures remain a relatively unexplored class of materials because of the challenge of stabilizing nonepitaxial interfaces. Here, we report an unusual reconstruction during the deposition of precursors when targeting the synthesis of heterostructures with an odd number of PbSe monolayers. Multilayer elemental precursors of Pb|Se + V|Se were deposited to have the correct number of atoms to form [(PbSe)1+δ]q(VSe2)1 where q is the number of PbSe monolayers in the heterostructure. Structural analysis of the self-assembled precursor via X-ray reflectivity, X-ray diffraction, and HAADF-STEM suggests three different behaviors upon deposition. Precursors with q ≥ 7 and even values of q have the targeted nanoarchitectures after deposition, which are maintained as the products are self-assembled through a near diffusionless process. Significant lateral surface diffusion occurred during the deposition of precursors with q = 1, 3, and 5, resulting in the precursor to have a different nanoarchitecture than targeted. Additional perpendicular long-range diffusion occurs during self-assembly of these precursors, resulting in different final products than targeted. Density functional theory (DFT) calculations of PbSe blocks show that the odd-numbered layers are less stable than the even-numbered layers, which suggests an energetic driving force for the observed rearrangement. This work highlights the importance of understanding the reaction mechanism when attempting to prepare 2D layers of constituents with bulk 3D structures.

Band gap engineering and enhancement of electrical conductivity in hydrothermally synthesized CeO2 ̶ PbS nanocomposites for solar cell applications

The wide band gap of CeO2 limits its application in solar energy harvesting, notwithstanding the exceptional optical and electrical properties due to the presence of unfilled 4f orbitals. Therefore, we combine a narrow band gap semiconductor PbS with CeO2 for band gap narrowing and to achieve enhanced electrical conductivity in the nanocomposites. CeO2 ̶ PbS nanocomposites were synthesized from a combination of as-prepared CeO2 powder and precursors of lead and sulphur using a two-step hydrothermal reaction process. The morphologies and structures of various nanocomposites synthesized at different concentrations of Pb precursor were studied by Field Emission Scanning Electron Microscopy and X-ray diffraction. The average crystallite sizes of the nanoparticles were estimated from XRD analysis and found to be in the range of 11 ̶ 15 nm for all the CeO2 ̶ PbS nanocomposites. The homogeneity and chemical composition were investigated by Energy Dispersed X-ray Analysis and X-ray photoelectron spectroscopy. Similarly, the microstructure study and lattice imaging were carried out with the help of high-resolution transmission electron microscopy. The lattice structure was corroborated by lattice vibration properties studied by micro-Raman spectroscopy. The surface structure and composition, such as the identification of surface functional group and adsorbed species were ascertained with the help of Fourier Transform Infrared Spectroscopy. The optical properties of the CeO2 ̶ PbS were studied by UV–Vis Diffuse Reflectance Spectroscopy. The optical band gaps of the nanocomposites were estimated to be 2.76 ̶ 2.98 eV. The electrical property of the CeO2 ̶ PbS powder was analyzed by recording the current-voltage characteristics of a series of hydraulic pressed pellets. The electrical conductivity obtained for CeO2 ̶ PbS nanocomposites was found to be much higher than that of pristine CeO2 nanoparticles. Hence, the enhanced electrical property with reduced band gap of CeO2 ̶ PbS nanocomposites makes it suitable for optoelectronic devices and solar cell applications.

Nanoconfinement and Interfacial Effect of Pb Nanoparticles into Nanoporous Carbon as a Longer-Lifespan Negative Electrode Material for Hybrid Lead–Carbon Battery

A homogeneous incorporation of nanosized Pb particles into the pores and surface of carbon, is reported for developing an advanced and hybrid lead–carbon battery system. The 30% Pb precursor with c...

Room Temperature In-Situ Synthesis of Inorganic Lead Halide Perovskite Nanocrystals Sol Using Ultraviolet Polymerized Acrylic Monomers as Solvent and Their Composites with High Stability

As a kind of promising optoelectrical material, all-inorganic perovskite nanocrystals CsPbX3 (X = Cl, Br, I) have attracted much attention, due to their excellent optoelectrical characteristics, in recent years. However, their synthesis approaches require rigorous conditions, including high temperature, eco-unfriendly solvent or complex post-synthesis process. Herein, to overcome these issues, we reported a novel facile room temperature in-situ strategy using ultraviolet polymerizable acrylic monomer as solvent to synthesis CsPbX3 nanocrystals without a complex post-synthesis process. In this strategy, adequate soluble precursors of Cs, Pb and Br and reaction terminating agent 3-aminopropyltriethoxysilane (APTES) were used. The obtained CsPbBr3 nanocrystals showed a high photoluminescence quantum yields (PLQY) of 87.5%. The corresponding polymer composites, by adding light initiator and oligomer under ultraviolet light radiation, performed excellent stability in light, air, moisture and high temperature. The reaction process and the effect of the reaction terminating agent have been investigated in detail. This strategy is a universal one for synthesizing CsPbX3 nanocrystals covering visible light range by introducing HCl and ZnI2.

Strategic separation of metal sulfides from residual wet-chemical precursors for synchronous production of pure water and nanostructured photocatalysts

Pseudo successive ionic layer adsorption and reaction (p-SILAR) is an emerging technique for deposition of quantum dots (QDs) on a variety of nanoparticles (NPs); however, it has a limitation of wastage of water-based ionic precursors those are hazardous in nature as well. In this study, we have strategically ensured the removal of ionic species from aqueous solutions, by salvaging efficient metal sulfides (i.e. PbS, CdS, ZnS, CuS, Ag2S, and SnS) exhibiting 62%, 47%, 66%, 86%, 91%, and 99% degradation of Congo-red dye, respectively, resulting a reaction rate of 0.016, 0.011, 0.021, 0.034, 0,083, and 0.04 min−1. The qualitative characterization of successfully salvaged metal sulfide photocatalysts was carried out using scanning and transmission electron microscopy (SEM/TEM), coupled with optical, crystallographic, and elemental elucidation. Importantly, residual aqueous ionic solutions were detoxified and water was brought back to its pure and drinkable state, avowing the standardization of wastewater treatment bi-effectually. Specifically, anionic precursors having pH value of ~ 12 and cationic precursors of SnCl2 and Pb(NO3)2 having pH values of ~ 4 were taken to 7.

Synthesis and characterization of lead (IV) precursors and their conversion to PZT materials through a CVD process

New Pb(IV) precursors for lead zirconate titanate (PZT) thin films were synthesized, and their solid-state structures were elucidated by single-crystal X-ray crystallography. First, tetraphenyl lead (Ph4Pb) was synthesized from the reaction of PbCl2 with the Grignard reagent, PhMgBr, by a published method. Two of the phenyl ligands in Ph4Pb were replaced by bromines, and then were substituted with bis(trimethylsilyl)amides (btsa) to yield Ph2Pb(btsa)2 (1), or with 2,2,6,6-tetramethyl-3,5-heptadiketonate (thd) ligands to yield Ph2Pb(thd)2 (2). Single crystals of these two new Pb(IV) precursors were obtained by recrystallization in hexane, and their chemical compositions were characterized by FT-IR and 1H NMR. In TG analyses, both compounds exhibited sharp decomposition curves, with major mass losses in the region of 200–250 °C. PZT films were fabricated from one of the newly prepared Pb(IV) precursors by an MOCVD process involving Ti(OiPr)4 and Zr(OPr)4, and the development of the perovskite phase with temperature was monitored by an XRD method.

Effective Preparation of Nanoscale CH3NH3PbI3 Perovskite Photosensitizers for Mesoporous TiO2‐Based Solar Cells by Successive Precursor Layer Adsorption and Reaction Process

Nanoscale CH3NH3PbI3 perovskite sensitizers are grown by delivering each precursor successively onto the surface of mesoporous (meso) TiO2 electrodes. Using Pb(NO3)2 ions as a lead(II) source and CH3NH3I (MAI) for methylammonium and iodide sources, repetitive cycles of the two dipping steps are successful in growing few nanometer‐sized MAPbI3 gradually on the TiO2 surface inside the meso‐TiO2 film. However, some aggregates are observed on the top surface of the meso‐TiO2 film due to slight dissolution of PbI2 and its accumulation/reaction with MAI at the top surface of the meso‐TiO2 film. To solve this inhomogeneity of the deposition, a nondestructive multiple deposition route for nanoscale MAPbI3 is suggested as a successive precursor layer adsorption and reaction (SPLAR) process where, from the second cycle of deposition, PbI2 is delivered with the help of an ionic liquid compound dissolved in dichloromethane. With this new Pb precursor in less‐polar solvents, nanoscale MAPbI3 sensitizers are grown without dissolution of preformed perovskites or formation of some aggregates at the top surface. After the third cycle of SPLAR deposition, about 7.0 nm–sized MAPbI3 sensitizers are prepared and display enhanced photovoltaic performance (7.18 ± 0.31%) compared with devices obtained from only one cycle (5.74 ± 0.30%).