Colloidal lead-free Cs2AgBiBr6 double perovskite nanocrystals: Synthesis,uniform thin-film fabrication,and application in solution-processed solar cells

Recently developed lead-free double perovskite nanocrystals(NCs)have been proposed for the possible application in solutionprocessed optoelectronic devices.However,the optoelectronic applications of double perovskite NCs have been hampered due to the structural and chemical instability in the presence of polar molecules.Here,we report a facile strategy for the synthesis and purification of Cs₂AgBiBr₆double perovskite NCs that remained stable even after washing with polar solvent.This is realized with our efficient colloidal route to synthesize Cs₂AgBiBr₆NCs that involve stable and strongly coordinated precursor such as silvertrioctyl phosphine complex together with bismuth neodecanoate,which leads to a significantly improved chemical and colloidal stability.Using layer-by-layer solid-state ligand exchange technique,a compact and crack-free thin film of Cs₂AgBiBr₆NCs were fabricated.Finally,perovskite solar cells consisting of Cs₂AgBiBr₆as an absorber layer were fabricated and tested.     

Synthesis and Photocatalytic Application of Stable Lead‐Free Cs2AgBiBr6 Perovskite Nanocrystals

Lead halide perovskite nanocrystals (NCs) have demonstrated great potential as appealing candidates for advanced optoelectronic applications. However, the toxicity of lead and the intrinsic instability toward moisture hinder their mass production and commercialization. Herein, to solve such thorny problems, novel lead‐free Cs₂AgBiBr₆ double perovskite NCs fabricated via a simple hot‐injection method are reported, which exhibit impressive stability in moisture, light, and temperature. Such materials are then applied into photocatalytic CO₂ reduction, achieving a total electron consumption of 105 µmol g^?1 under AM 1.5G illumination for 6 h. This study offers a reliable avenue for Cs₂AgBiBr₆ perovskite nanocrystals preparation, which holds a great potential in the further photochemical applications.     

Tuning the Structural and Optoelectronic Properties of Cs2AgBiBr6 Double-Perovskite Single Crystals through Alkali-Metal Substitution

Lead-free double perovskites have great potential as stable and nontoxic optoelectronic materials. Recently, Cs₂AgBiBr₆ has emerged as a promising material, with suboptimal photon-to-charge carrier conversion efficiency, yet well suited for high-energy photon-detection applications. Here, the optoelectronic and structural properties of pure Cs₂AgBiBr₆ and alkali-metal-substituted (Cs_1−xY_x)₂AgBiBr₆ (Y: Rb⁺, K⁺, Na⁺; x = 0.02) single crystals are investigated. Strikingly, alkali-substitution entails a tunability to the material system in its response to X-rays and structural properties that is most strongly revealed in Rb-substituted compounds whose X-ray sensitivity outperforms other double-perovskite-based devices reported. While the fundamental nature and magnitude of the bandgap remains unchanged, the alkali-substituted materials exhibit a threefold boost in their fundamental carrier recombination lifetime at room temperature. Moreover, an enhanced electron–acoustic phonon scattering is found compared to Cs₂AgBiBr₆. The study thus paves the way for employing cation substitution to tune the properties of double perovskites toward a new material platform for optoelectronics.     

ZnO single crystals: Synthesis and characterization

Zinc oxide crystals grown in a single basic mineralizer in hydrothermal autoclaves are of poor quality. The crystals are transparent, pale green or pale yellow in color depending on different technical growth conditions. The quality of crystals under different conditions was observed by X-ray rocking curves measurement. The use of ultra-pure nutrient improves their perfection and purity. Zinc oxide bulks that were grown by the hydrothermal method in a mixture of KOH and LiOH aqueous solutions are of good quality.     

VOC over 1.2 V for Cs2AgBiBr6 solar cells based on formamidinium acetate additive

Cs₂AgBiBr₆ is a lead-free perovskite that shows great potential to solve the toxicity and instability of organic–inorganic lead perovskite. However, because of the poor interface contact and inferior film quality, the open-circuit voltage and the power conversion efficiency of the solar cells are inhibited. Herein, the Cs₂AgBiBr₆ film quality is improved by adding formamidinium acetate into the precursor solution. With additive regulation, the grain size increases and the film surface is more smooth. The crystal structure remains unchanged, and the defect density decreases. Correspondingly, the average power conversion efficiency of the target device increases more than 30% than the control device. The best efficiency approaches 2.09%, and the open-circuit voltage is surprisingly high at 1.23 V, the highest value reported for Cs₂AgBiBr₆ solar cells. Moreover, the device remains more than 90% of its initial efficiency after 40 days of storage under environmental conditions, showing excellent stability. This work is therefore helpful for enhancing the efficiency and stability of inorganic lead-free perovskite solar cells toward future commercialization.

     

Cs2TiI6:A potential lead-free all-inorganic perovskite material for ultrahigh-performance photovoltaic cells and alpha-particle detection

The lead contamination and long-term stability are the two important problems limiting the commercialization of organic-inorganic lead halide perovskites.In thi...     

Growth and characterization of RuO2 single crystals

Using the vapor transport technique in a flowing oxygen system, we have grown the largest single crystals of RuO₂ ever reported (10 mm × 5 mm × 5 mm). Polycrystalline RuO₂, a mixture of polycrystalline RuO₂ and purified Ru metal powder, or purified Ru metal powder were used as the starting material. Optimum conditions are given for growing large high quality crystals. The morphology, stoichiometry and resistivity of selected single crystals of RuO₂ are discussed.     

Luminescence and scintillation properties of Cs3BiCl6 crystals

The optical and scintillation properties of Cs₃BiCl₆ single crystals were characterized, and absorption properties were investigated for thin films. The thin films showed two absorption bands at ∼220 nm and 330 nm; these bands can be attributed to the ¹A_1g → ¹T_1u and ¹A_1g → ³T_1u transitions of Bi³⁺ ions, respectively. A luminescence band was observed at ∼390 nm in the photoluminescence spectra; this band can be attributed to the ³T_1u → ¹A_1g transition of Bi³⁺ ions. In the X-ray-induced radioluminescence spectrum, in addition to the luminescence band at 390 nm, another band was observed at 600–700 nm; this band was tentatively attributed to the radiative recombination of self-trapped excitons. The decay-time constants of photoluminescence and scintillation decay were of the order of nanoseconds. The scintillation light yield was 800 photons/MeV. The results indicate that Cs₃BiCl₆ has a fast scintillation decay and a relatively poor light yield.     

Defect characterization of KTP single crystals

Potassium titanyl phosphate (KTP) is a relatively new nonlinear optical material with excellent combination of physical properties. This paper presents the combined etching and X-ray topographic studies carried out on KTP crystals with a view to characterizing their defects. KTP crystals employed in this investigation were grown from flux. Optical microscopic study of habit faces revealed growth layers and growth hillocks on (100) and (011) faces respectively. Etching of (011) habit faces proved that growth hillocks corresponded to the emergence point of dislocation out crops on these faces. The suitability of the new etchant to reveal dislocation was confirmed by etching the matched pairs obtained by cleaving. The defects present in the crystal were also studied by X-ray topography. The defect configuration in these crystals is characteristic of crystals grown from solution. The dislocations arc predominantly linear with their origin either at the nucleation centre or inclusions. In general, grown crystals were found to have low dislocation density and often large volumes of crystals free from dislocation could be obtained.     

钙钛矿型氧化合物AgNbO3的水热合成与表征

采用水热法制备了钙钛矿型化合物Ag-NbO3晶体,对化合物进行粉末X射线表征。Rietveld精修结果表明化合物AgNbO3属于三方晶系,空间群为R-3C。并对化合物进行了扫描电子显微镜(SEM)、BET法测定比表面积和对固体紫外漫反射光谱进行表征。对该化合物的光催化性质进行了测试,在可见光照射下降解染料龙胆紫。结果表明此化合物在室温下具有很高的光催化性质,在光催化性能方面具有潜在的应用价值。     

Growth of CuInTe2 single crystals by iodine transport and their characterization

The single crystals with stoichiometry close to 1:1:2 of CuInTe₂ (CIT) have been grown by chemical vapor transport (CVT) technique using iodine as the transporting agent at different growth temperatures. Single crystal X-ray diffraction studies have confirmed the chalcopyrite structure for the grown crystals and the volume of unit cell is found to be the same for the crystals grown at different conditions. Energy dispersive X-ray (EDAX) analysis of CIT single crystals grown shows almost the same stoichiometric compositions. Scanning electron microscope (SEM) analysis reveals kink, step and layer patterns on the surface of CIT single crystals depending on the growth temperatures. The optical absorption spectra of as-grown CIT single crystals grown at different conditions show that they have same band gap energies (1.0405 eV). Raman spectra exhibit a high intensity peak of A₁ mode at 123 cm^?1. Annealed at 473 K in nitrogen atmosphere for 40 h CIT single crystals have higher hole mobility (105.6 cm²V^?1s^?1₎ and hole concentration (23.28 × 10¹⁷ cm^?3) compared with values of hole mobility (63.69 cm² V^?1 s^?1) and hole concentration (6.99 × 10¹⁵ cm^?3) of the as-grown CIT single crystals.     

Growth and characterization of Ni substituted Bi2Se3 single crystals

Journal of Superconductivity and Novel Magnetism - In this article, we report synthesis and magneto-transport analysis of Ni substituted Bi2Se3 crystals. Phase purity and crystalline growth are...     

Lead‐Free Double Perovskite Cs2SnX6: Facile Solution Synthesis and Excellent Stability

Long‐term instability and possible lead contamination are the two main issues limiting the widespread application of organic–inorganic lead halide perovskites. Here a facile and efficient solution‐phase method is demonstrated to synthesize lead‐free Cs₂SnX₆ (X = Br, I) with a well‐defined crystal structure, long‐term stability, and high yield. Based on the systematic experimental data and first‐principle simulation results, Cs₂SnX₆ displays excellent stability against moisture, light, and high temperature, which can be ascribed to the unique vacancy‐ordered defect‐variant structure, stable chemical compositions with Sn⁴⁺, as well as the lower formation enthalpy for Cs₂SnX₆. Additionally, photodetectors based on Cs₂SnI₆ are also fabricated, which show excellent performance and stability. This study provides very useful insights into the development of lead‐free double perovskites with high stability.     

Analysis of eco-friendly tin-halide Cs2SnI6-based perovskite solar cell with all-inorganic charge selective layers

Journal of Materials Science: Materials in Electronics - In this research work, eco-friendly and tin-halide Cs2SnI6-based perovskite coupled with the various all-inorganic charge collective layers...     

The synthesis of aluminum nitride single crystals

Small bipyramidal (1.1 mm long × 0.3 mm wide), good optical quality aluminum nitride single crystals have been reproducibly grown from molten AlNCa₃N₂ solutions.     

Boosting triplet self-trapped exciton emission in Te(IV)-doped Cs2SnCl6 perovskite variants

Perovskite variants have attracted wide interest because of the lead-free nature and strong self-trapped exciton (STE) emission. Divalent Sn(II) in CsSnX3 perovskites is easily oxidized to tetravalent Sn(IV), and the resulted Cs2SnCl6 vacancy-ordered perovskite variant exhibits poor photoluminescence property although it has a direct band gap. Controllable doping is an effective strategy to regulate the optical properties of Cs2SnX6. Herein, combining the first principles calculation and spectral analysis, we attempted to understand the luminescence mechanism of Te4+-doped Cs2SnCl6 lead-free perovskite variants. The chemical potential and defect formation energy are calculated to confirm theoretically the feasible substitutability of tetravalent Te4+ ions in Cs2SnCl6 lattices for the Sn-site. Through analysis of the absorption, emission/excitation, and time-resolved photoluminescence (PL) spectroscopy, the intense green-yellow emission in Te4+:Cs2SnCl6 was considered to originate from the triplet Te(IV) ion 3P1→1S0 STE recombination. Temperature-dependent PL spectra demonstrated the strong electron-phonon coupling that inducing an evident lattice distortion to produce STEs. We further calculated the electronic band structure and molecular orbital levels to reveal the underlying photophysical process. These results will shed light on the doping modulated luminescence properties in stable lead-free Cs2MX6 vacancy-ordered perovskite variants and be helpful to understand the optical properties and physical processes of doped perovskite variants.     

Hydrothermal synthesis and characterization of CsNiP and 2(LiZnHP2O7) crystals

CsNiP and 2(LiZnHP₂O₇) crystals were synthesized by hydrothermal technique at moderate P-T conditions. Solubility results of both the compound shown positive thermal coefficient and single crystal X-ray studies revealed, CsNiP crystallized in hexagonal system with cell parameters; a = 7.173(2), c = 5.944(9) Å, V = 264.87(7) ų and space group P63/mmc and 2(LiZnHP₂O₇) crystallized in orthorhombic system with cell parameters; a = 12.3636 Å, b = 27.5330 Å, c = 6.8647 Å and space group, Pca21 exhibiting ring type of cavities with open aperture in the structure. CsNiP is a frequency dependent paramagnetic and 2(LiZnHP₂O₇) is a diamagnetic.     

Photoelastic and acousto-optical properties of Cs2HgCl4 crystals

We use a Mach-Zehdner interferometric technique to study the piezo-optical properties of Cs2HgCl4 crystals at room temperature. All piezo-optical (pi(mn)) and photoelastic (p(in)) tensor constants are obtained. A substantial photoelastic effect and low ultrasonic velocities in these crystals determine a relatively high figure of merit M2 for isotropic diffraction (for a certain geometry of acousto-optical interactions, M2 approximately 110 x 10(-15) s3/kg). The new material may be considered, therefore, a candidate for applications in acousto-optical devices. The dependence of the acoustic walk-off angle on the direction of sound propagation is calculated for the principal crystallographic planes.