Crystal Growth Morphology Research Articles

Fabricating stable and efficient perovskite solar cells in air ambient via lattice anchoring strategy

The stability issue is becoming more and more important in the development of halide perovskite solar cells (PSCs). Various strategies have been adopted to explore the stability of perovskite films and devices. Nevertheless, most perovskite films are prepared in inert atmosphere, limiting the practical application of PSCs. Herein, lattice anchoring strategy was employed to prepare stable perovskite films in air ambient. The adopted bidentate anchor cations (BACs) could effectively inhibit the invasion by moisture and restrain organic component escaping from perovskite structure during preparation process. The steric and coulomb effects of embedded BACs have dual influence on the crystal growth process and morphology of perovskite films. The BACs are pinned on the crystal lattices and the surface of perovskite film without forming 2D perovskite, which would enhance the crystal intrinsic stability and moisture resistance. The modified CH3NH3PbI3 device power conversion efficiency (PCE) raises to 20.33%, and remains over 85% of the initial PCE during exposure to ambient air (humidity＞70 RH, temperature＞30 °C) for over 90 days. The lattice anchoring strategy provides a convenient method to improve the quality of perovskite films in air ambient.

Crystal morphology regulation of pronamide through solvent selection: Prediction and implementation

Molecular dynamics simulation was performed for the solvent selection to regulate the growth morphology of pronamide crystals using the attachment energy model. Five dominant crystal planes were revealed during morphology prediction of pronamide in vacuum, on basis of which the modified attachment energy model was employed to regulate the crystal morphology with three typical solvents (toluene, acetone and methanol) according to their electrostatic potential. Variable morphology of pronamide from needle-like, plate-like to bulk was predicted in the three solvents under the frame of this thermodynamic model. The pronamide crystals obtained from slow evaporation crystallization process were in good agreement with theoretical prediction, showing that molecular dynamics simulation could aid the solvent selection for the crystal morphology regulation effectively.

Tuning the Growth Morphology of Gypsum Crystals by Polymers

Tuning the Growth Morphology of Gypsum Crystals by Polymers

Modified hot plate method for synthesizing MoO3 nanoplates

Molybdenum trioxide (MoO3 ) with layered structures adopts exotic physical features, which has evoked an extensive interest in electronic and photoelectronic devices. Here, we report a low-cost, simplehandle, atmospheric-pressure, and rapid-synthesis technique for growing large-scale MoO3 crystals, i.e., a modified hot plate method. The growth rate and morphology of the MoO3 crystals were well controlled by changing source temperatures and substrates. Complementary measurements, including optical microscope, atomic force microscope, X-ray diffraction, Raman spectroscope, and scanning near-field optical microscope, were used to investigate the structural and physical properties. The results reveal that large-scale MoO3 crystals with well-defined crystallinity have been obtained. Meanwhile, surface hyperbolic phonon polaritons on as-prepared MoO3 crystal planes have also been observed, which may provide an attractive insight into nanoelectronic and nanophotonic devices.

The analysis of the nucleation process of the lithium germanium phosphate glass

The nucleation process of lithium germanium-phosphate glass was studied to determine the temperature range of nucleation and the temperature of the maximum nucleation rate. The differential thermal analysis (DTA), and scanning electron microscope (SEM) were used to reveal the nonisothermal and isothermal process of nucleation, respectively. The crystallization process occurred at a high homogeneous nucleation rate and the spherulitic crystal growth morphology. Nanostructured samples were obtained.

Visible-light driven efficient elimination of organic hazardous and Cr (VI) over BiOCl modified by Chinese Baijiu distillers’ grain-based biochar

In this paper, distillers’ grains biochar (DGBC) was facilely gained by processing the distillers’ grains produced in Chinese Baijiu brewing, and the DGBC was used to modify BiOCl. The prepared DGBC/BiOCl composite photocatalysts show elevated visible light-driven catalytic performance. X-ray diffraction (XRD) and scanning electron microscope (SEM) suggest the presence of DGBC affects the crystal growth and microscopic morphology of BiOCl. The low-temperature electron paramagnetic resonance (EPR) test affirms more oxygen vacancies (OVs) exist in the DGBC/BiOCl composite photocatalysts. The 0.75-DGBC/BOC photocatalyst holds the highest efficiency for removal of rhodamine B (RhB), tetracycline (TC) and Cr (VI) compared with BiOCl, commercial TiO2 (P25) and other DGBC/BiOCl composites. Given the experimental results, the enhanced visible light responsive performance originates from the rich OVs introduced by the modification of BiOCl with DGBC and the higher separation rate of photoexcited carriers.

Crystal growth and design of Sn-doped β-Ga2O3: Morphology, defect and property studies of cylindrical crystal by EFG

The cylindrical Sn: β-Ga2O3 crystal with high crystalline quality was successfully designed and grown by the innovative edge-defined film-fed growth (EFG) method equipped with a cylindrical Iridium die. The challenges for the growth of Sn: β-Ga2O3 crystals were overcome by optimizing the design of an afterheater. The growth morphology of cylindrical β-Ga2O3 crystal was studied using a theoretical model and the results from experimental crystal growth. The order of importance of growth conditions affecting β-Ga2O3 crystal growth morphology was examined, based on the morphological features of cylindrical β-Ga2O3 crystals obtained by the EFG and Czochralski methods. The iridium inclusions with three shapes were observed in bulk β-Ga2O3 crystal, and the formation mechanism was carefully discussed. The optical bandgap and valence band maximum (VBM) of Sn: β-Ga2O3 crystal were calculated to be 4.74 eV and 3.49 eV by absorption spectra and X-ray photoelectron spectroscopy (XPS), respectively. The corresponding surface barrier height (Φsurf) was 1.25 eV. The carrier concentration of 5.95 × 1018 cm−3 was characterized by capacitance-voltage (C-V) measurement. By the Hall measurement, the carrier mobility and resistivity were estimated to be around 51 cm2 V−1 s−1 and 3.55 × 10–2 Ω cm, respectively.

Effects of boron doping on the fabrication of dense 6H-SiC ceramics by high-temperature physical vapor transport

In this paper, boron-doped dense 6H-SiC ceramics was fabricated by the high-temperature physical vapor transport (HTPVT) method. The effect of B doping on the crystal structure stability of 6H-SiC was investigated based on density functional theory (DFT). The results show that B doping can be realized even under thermodynamical equilibrium conditions. Nevertheless, it is found that the B doping effects on the (0001) of Si-plane and (000-1) of C-plane are significantly different. The doping experiments demonstrated that B can observably change the crystal growth morphology, leading to the formation of elongated 6H-SiC crystals.

Investigation of (001), (010), and (100) surface termination and surface energies of the Zintl Ca5Ga2Sb6

Zintl Phases are a class of intermetallic compounds that combine ionic and covalent bonding to form charge-balanced structures, leading to semiconducting properties. The Ca5M2Sb6 family of Zintl compounds, (M =Al, Ga, In), have demonstrated promising thermoelectric efficiency, meaning they can be used to convert a temperature gradient into useful electrical energy. Ca5M2Sb6 compounds crystallize in a highly anisotropic structure comprised of chains of corner-linked MSb4 tetrahedra, in which each neighboring chain is joined via Sb-Sb covalent bonds, forming an infinite polyanionic “ladder”. In the present study, we used first principles calculations to study various surface terminations of the Ca5Ga2Sb6 structure as a mechanism to understand its crystal growth morphology. Our results indicate that the calcium stoichiometry of the crystal surface plays an important role in surface reconstruction, specifically leading to the formation or breaking of covalent bonds. Our results suggest that surface energy as a function of stoichiometry and crystallographic orientation is only one piece of the puzzle in understanding the growth habits of Ca5Ga2Sb6 crystals.

Crystal Growth Kinetics in GeS2 Glass and Viscosity of Supercooled Liquid.

The crystal growth kinetics and morphology in germanium disulfide bulk glass and glass surface is described. The structural relaxation taking place below the glass transition is slow and the corresponding volumetric change is negligible. Therefore, it does not affect substantially the crystal growth process. The crystal growth rate of low temperature β-GeS2 and high temperature α-GeS2 polymorphs in the bulk glass is comparable, being slightly decoupled from the shear viscosity below the glass transition. The crystal growth rate of β-GeS2 in an amorphous thin film of the same composition is several orders of magnitude faster than that at the surface of bulk glass. This fast surface crystal growth is strongly decoupled from viscosity. Such behavior resembles the glass-to-crystal fast growth mode observed by several authors in some organic molecular glasses. Taking into account previously reported viscosity and heat capacity data, the crystal growth kinetics of both polymorphs can be quantitatively described by the 2D surface growth model for low and high supercooling. The nonisothermal differential scanning calorimetry experiments are analyzed, providing evidence of a complex nature of the overall crystallization process with apparent activation energy comparable to that obtained from isothermal microscopy measurement of crystal growth in the same temperature range.

EFFECT OF ANISOTROPIC SURFACE TENSION ON THE GROWTH OF COLUMNAR CRYSTALS IN TERNARY UNDERCOOLED MELTS

The effect of anisotropic surface tension on the growth of columnar crystals in ternary melt is studied, and the approximate analytical solution of the growth morphology of columnar crystals is given. It is found that in the initial stage of growth, some parts of the interface grow outward, while some parts first grow inward, and grow outward together with other parts after reaching a certain depth, which makes the columnar crystal interface form a remarkable concave and convex formation. Compared with the case in the pure melt and ternary alloy melt, the component added in the ternary alloy melt decreases the effect of the anisotropic surface tension.

Hydrothermal synthesis conditions effect on hierarchical ZnO/CuO hybrid materials and their photocatalytic activity

In the current study, we have explored the consequences of synthesis conditions on optical, morphological, and photoluminescence characteristics of hybridized ZnO nanocomposites. The photodegradation kinetics of Triclopyr, a pesticide, using hydrothermally synthesized ZnO/CuO materials at various synthesis conditions were also studied. The prepared samples were characterized by various techniques such as UV-vis spectrophotometer, field emission scanning electron microscopy (FESEM), elemental dispersive X-ray analysis, and photoluminescence spectrometer. From FESEM images, it was revealed that the synthesis conditions greatly influence the morphology of nanomaterials, particle size, nucleation, and crystal growth. To evaluate the percentage composition of elements present in synthesized materials, elemental analysis with mapping was performed. The band gap values were calculated using Kubelka Munk’s plot. The band gap values decrease on CuO incorporation and lie near infrared region. Effect of scavengers and pH on degradation kinetics were also explored. The complete mineralization of Triclopyr was achieved in 100 min. The synthesized materials are found energy efficient and helpful in environmental purification.

Controlling the aqueous growth of urea crystals with different growth inhibitors: a molecular-scale study.

Molecular scale understanding of the mechanism of solution-mediated nucleation and the growth of crystalline materials in the presence of growth inhibitors together with the process parameters continues to attract the interest of the scientific community though much headway has been made in recent years. Growth inhibitors can be added to solution of a crystallizing parent molecule to alter the rate of growth of different crystal faces, size and shape of the crystalline materials. In this work, we investigated the effects of a number of shape-controlling inhibitors, such as acetone, biuret and biurea, on the growth kinetics of the various faces of aqueous-grown urea crystals as a means to predictably control the crystal growth morphology. We combined the adsorption energy landscape of various auxiliaries with the kinetics of the molecular growth processes to develop an analytical model to compute the rate of growth as a function of supersaturation and the additive concentration. The model relates the kinetic and thermodynamic aspects of the adsorption of the solute, solvent and additive to provide a quantitative description of the crystal growth. Ab initio periodic dispersion-corrected density functional theory using the hybrid exchange–correlation functional was employed to determine the interfacial structure of the adsorption of various auxiliaries at crystalline surfaces. The calculated adsorption energies of different auxiliaries were employed to examine the role played by these auxiliaries during the aqueous crystallization of urea crystals containing small amounts of additives. Our results showed that the growth of (110), (111) and (1̄1̄1̄) faces were nearly unaltered by the addition of moderate amounts of acetone as it has lower adsorption energies with the surfaces of these faces. Nevertheless, the presence of acetone in the solution reasonably impeded the growth of the (001) face. The addition of biuret or biurea in the solution led to a higher adsorption energy at (001) and (111) faces. Consequently, the low concentration of these additives severely obstructed the growth of (001) and (111) faces as most of the adsorption sites were occupied by these additives. On the other hand, these additives were weakly adsorbed at the (110) face and, hence, the growth of the (110) face largely remained unaltered. Moreover, unlike biuret, biurea considerably inhibited the growth of the (1̄1̄1̄) face. Our results are in agreement with the experimental and computational results reported in the literature.

Improvement of Colloidal Characteristics in a Precursor Solution by a PbI2-(DMSO)2 Complex for Efficient Nonstoichiometrically Prepared CsPbI2.8Br0.2 Perovskite Solar Cells

The optoelectronic properties of all-inorganic perovskite solar cells are greatly affected by the quality characteristics of films, such as the defect concentration, crystal growth orientation, crystallinity, and morphology. In this study, a PbI2-(DMSO)2 complex is adopted to partially replace PbI2 as the lead source in the preparation of perovskite precursor solutions. Due to the rapid dispersion of the PbI2-(DMSO)2 complex in a solvent, raw materials can rapidly react to form perovskite colloids with a narrow size distribution. Such uniform colloidal particles are found to be beneficial for achieving films with improved quality and highly orientated growth along the [001] direction. The optimized film exhibits a clearly improved crystallinity and a decrease in defect concentration from 4.29 × 1015 cm-3 to 3.20 × 1015 cm-3. The device based on the obtained all-inorganic CsPbI2.8Br0.2 perovskite finally achieves an increase in photovoltaic power conversion efficiency from 10.5 to 14.15%. In addition, the environmental stability of the device also benefits from the improved film quality. After 480 h of storage in air, the device can still maintain nearly 80% of its initial performance.

Spinel CoFe2O4 /carbon nanotube composites as efficient bifunctional electrocatalysts for oxygen reduction and oxygen evolution reaction

In the development of fuel cells, it is the key to large-scale commercialization of fuel cells to rationally design and synthesize efficient and non-noble metals-based bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this paper, spinel CoFe2O4/carbon nanotube composites (CoFe2O4/CNTs/FA) were synthesized by solvothermal and calcination method. XRD, TEM, XPS and BET characterizations indicate that the addition of complexing agent fumaric acid can improve the crystal growth kinetics and morphology of CoFe2O4/CNTs nanohybirds. The as-synthesized CoFe2O4/CNTs/FA pyrolyzed at 500 °C have an outstanding bifunctional catalytic activity for ORR and OER with the potential of 1.62V (vs. RHE) at a current density of 10 mA/cm2 and half-wave potential E1/2 = 0.808V (vs. RHE) in alkaline electrolyte, respectively. It is obviously better than unloaded CoFe2O4 nanoparticles and commercial CNTs. CoFe2O4/CNTs/FA also exhibit better methanol tolerance ability and durability than commercial Pt/C and RuO2 catalyst. This investigation broadens an idea of simple compounding of spinel with carbon-based materials to improve electrochemical properties.

Zoned Crystal Records of Transcrustal Magma Transport, Storage and Differentiation: Insights from the Shatsky Rise Oceanic Plateau

AbstractMagmatic processes occurring in the deepest parts of sub-volcanic plumbing systems remain poorly constrained. However, crystal mush fragments incorporated into ascending magmas can provide valuable insights into the processes and conditions of transcrustal magma transport, storage and differentiation. Here we use lava samples drilled from Tamu Massif, Shatsky Rise, to understand the magmatic processes taking place in a region of thickened oceanic crust. We observe correlations between crystal textures and compositional zones in plagioclase that reveal relationships between mechanisms of magmatic differentiation and the crustal depths at which they occurred. When combined with geothermobarometric models, our observations indicate that deep crustal crystal storage took place in high-crystallinity mushes at two discrete levels (∼17 and ∼27 km depth). Diffusive constraints from crystal zoning lengthscales indicate that the lifetime of crystals within the mushes exceeded several thousand years. Magmatic recharge was frequent and produced various dissolution textures in plagioclase. In contrast, shallow crystal storage (∼2·4 km depth) took place in a liquid-dominated domain where crystal residence times were much shorter. Crystal zoning patterns indicate that magmas transporting crystals from the deepest environment to the surface sometimes accumulated additional crystals from mid-crustal storage regions and sometimes did not, highlighting the complexity of magma assembly processes. Temperature contrasts in the lower crust at Shatsky Rise are probably low, owing to extensive magma input and a paucity of hydrothermal cooling at depth. Crystal growth morphologies are consequently relatively simple. Crystallization in thick and thermally mature crusts may therefore lead to less complexity in crystal textures than crystallization in thinner crusts where temperature contrasts are higher. Our observations indicate that combining thermobarometry with studies of crystal textures and crystal compositions is a powerful approach for improving our understanding of magmatic differentiation and magma ascent paths.

Phase segregation controlled semiconductor crystallization for organic thin film transistors

Abstract In this article, we provide an in-depth review of important works on phase segregation which occurs as a result of mixing organic semiconductors with polymeric additives. Throughout the discussion, the indispensable correlations among phase segregation, crystal growth, layer structure and film morphology are showcased using specific examples that mainly entail small-molecule organic semiconductors such as 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) and 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (diF-TES-ADT). The various factors that impact the phase segregation are analyzed, which include surface energy, solvent choice, additive nature, and substrate interaction. The beneficial effects of phase segregation on charge transport and operational stabilities of organic semiconductor based organic thin film transistors (OTFTs) are also assessed. We believe that the phase segregation examples discussed in this work shed light on optimizing the electrical performance of organic semiconductors and unlock favorable features useful for their application in high-performance organic electronics on flexible substrates.

Effect of straining flow on growth of columnar crystal in ternary undercooled melt

As an important microstructure, columnar crystal growth technology, especially the growth technology of single columnar crystal plays an important role in improving the performances of semiconductor, optical devices and other related products. In many practical applications, because the alloy is composed of multi-component and there is inevitably flow in the melt, it is necessary to study the growth of columnar crystals in multi-component melt with flow separately. The growth of columnar crystal in a ternary undercooled melt subjected to straining flow under non-isothermal conditions is studied, and the approximate analytical expression for growth morphology of columnar crystal is given by using asymptotic method. It can be seen from the expression that straining flow is an important reason for irregular columnar crystal. When analyzing the effect of straining flow on the growth of columnar crystal in ternary melt, it is found that the incoming flow accelerates the growth velocity of the interface, while the outgoing straining flow reduces the growth velocity of the interface, namely, the straining flow makes the interface of columnar crystal deformed. At the same time, it is found that the interface deformation becomes more intense with the increase of flow velocity. The above conclusion can also be applied to the effect of straining flow on the interface morphology of columnar crystal in pure melt and binary melt. The comparison of the effects of straining flow on the interface of columnar crystal among pure melt, binary melt and ternary melt, shows that the interface morphology of columnar crystal in dilute alloy melt is more affected by straining flow than in the pure melt, but the more components are more easily affected by flow. However, the number of components in melt is not a decisive factor for the change of interface morphology of the columnar crystal, but the constitutional undercooling is an important factor for determining the interface morphology of multicomponent alloy. According to the conclusion of this paper, the influence of straining flow on the interface morphology of columnar crystal growth can be quantitatively predicted, which provides the necessary theoretical guidance in accurately controlling the interface morphology in the future.

Enhancing impurities removal from Si by controlling crystal growth in directional solidification refining with Al–Si alloy

In this paper, the principle of “plain materials” was attempted to advancing silicon (Si) purity, i.e., controlling solid-liquid interface and Si crystal growth pattern to enhance impurities removal from Si in directional solidification refining with Al–Si alloy. The relationship between Si crystal growth and impurity removal was established, and it was found that the removal ratio of metal impurities (less than 95% to more than 99%) gradually decreased with the order evolution of Si crystal from bulk Si, porous Si, acicular Si to Al–Si eutectic alloy. More than 99.5% of metallic impurities could be removed in the case of bulk silicon. However, the removal of boron (B) and phosphorus (P) showed the opposite trend. According to the principle of constitutional supercooling, the crystal Si growth and interface morphology were evaluated based on the conservation of mass of silicon atoms at the solidification interface, which was also used to explain the mechanism of impurities removal. Control of silicon crystal growth was achieved by changing the temperature gradient (lowering rate), Si alloy composition (Si content) and the heat transfer mode of solid-liquid interface that was expressed in terms of the effective heat transfer area ratio between wall and bottom of crucible (LA). A more stable and flat liquid-solid interface and 45% bulk Si was obtained at a lowering rate of 0.05 mm/min when the value of LA was 0.1, which can greatly enhance the removal of impurities.

The Impact of Salts on the Ice Recrystallization Inhibition Activity of Antifreeze (Glyco)Proteins.

Antifreeze (glyco)proteins (AF(G)Ps) have received increasing attention as potential cryopreservation agents since their discovery in the 1970s. While cryopreservation strategies for specific cells (such as red blood cells) are successful and widely implemented, preservation of other cell types, tissues and whole organs remains challenging. This is due to the multifactorial nature of the freeze-thaw damage, the complexity of preserving biological matter and the (country-to-country) variability of the employed procedures and regulations. AF(G)Ps are well-known for their ability to modulate ice crystal growth morphology and ice recrystallization inhibition (IRI), both of which are considered key contributors to freeze-thaw damage. To date, however, the impact of AF(G)Ps on cell survival remains at best partially understood as conflicting results on the benefits or disadvantages of including AF(G)P in cryopreservation strategies remain unelucidated. We hypothesize that variability in the additives in the cryopreservation media contributes to the observed discrepancies. To critically examine this idea, we monitored the inhibition of ice recrystallization by AF(G)P in the presence of various salts using a quantitative analysis of optical microscopy images via the Lifshitz-Slyozov-Wagner (LSW) theory for Oswald ripening. We found that the addition of salts, which are used in culture and cryopreservation media, enhances the IRI activity of AF(G)Ps, and that the magnitude of the enhancement was in line with the Hofmeister series. The size of ice crystals grown in AFGP1–5 and type III AFP samples containing chloride, phosphate and citrate ions were statistically smaller after 90 min of incubation than crystals grown in the absence of these salts. The ice recrystallization rates (kd) of AFGP1–5 and type III AFP samples prepared at a fixed overall ionic strength of 100 mM progressively decreased following the Hofmeister series for anions. Our results demonstrate that the performance of AF(G)Ps is significantly influenced by additives present in common cryopreservation media. It is thus important to conduct excipient compatibility experiments to identify potential incompatibilities between additives and AF(G)Ps in cryopreservation formulations.