Showing papers on "Crystallization published in 2015"
TL;DR: A rapid crystal growth process to obtain MAPbX3 single crystals, an order of magnitude faster than previous reports, and the grown crystals exhibit transport properties and trap densities comparable to the highest quality MAPb X3 reported to date.
Abstract: Single crystals of methylammonium lead trihalide perovskites (MAPbX3; MA=CH3NH3+, X=Br− or I−) have shown remarkably low trap density and charge transport properties; however, growth of such high-quality semiconductors is a time-consuming process. Here we present a rapid crystal growth process to obtain MAPbX3 single crystals, an order of magnitude faster than previous reports. The process is based on our observation of the substantial decrease of MAPbX3 solubility, in certain solvents, at elevated temperatures. The crystals can be both size- and shape-controlled by manipulating the different crystallization parameters. Despite the rapidity of the method, the grown crystals exhibit transport properties and trap densities comparable to the highest quality MAPbX3 reported to date. The phenomenon of inverse or retrograde solubility and its correlated inverse temperature crystallization strategy present a major step forward for advancing the field on perovskite crystallization. Hybrid perovskites are a promising class of materials for photovoltaic applications. Here, addressing the need for high-quality hybrid perovskite materials, the authors achieve the rapid growth of hybrid perovskite single crystals of high quality by inverse temperature crystallization.
1,448 citations
TL;DR: It is found that by using a non-halide lead source (lead acetate) instead of lead chloride or iodide, the perovskite crystal growth is much faster, which allows us to obtain ultrasmooth and almost pinhole-free perovSKite films by a simple one-step solution coating with only a few minutes annealing.
Abstract: To date, there have been a plethora of reports on different means to fabricate organic-inorganic metal halide perovskite thin films; however, the inorganic starting materials have been limited to halide-based anions. Here we study the role of the anions in the perovskite solution and their influence upon perovskite crystal growth, film formation and device performance. We find that by using a non-halide lead source (lead acetate) instead of lead chloride or iodide, the perovskite crystal growth is much faster, which allows us to obtain ultrasmooth and almost pinhole-free perovskite films by a simple one-step solution coating with only a few minutes annealing. This synthesis leads to improved device performance in planar heterojunction architectures and answers a critical question as to the role of the anion and excess organic component during crystallization. Our work paves the way to tune the crystal growth kinetics by simple chemistry.
829 citations
TL;DR: Solvent effects on the crystallization of the lead-free methylammonium tin triiodide (CH3NH3SnI3) perovskite films in a solution growth process are investigated to provide important progress toward achieving improved perovkite morphology control in realizing solution-processed highly efficient lead- free perovSKite solar cells.
Abstract: Organo-lead halide perovskite solar cells have gained enormous significance and have now achieved power conversion efficiencies of ∼20% However, the potential toxicity of lead in these systems raises environmental concerns for widespread deployment Here we investigate solvent effects on the crystallization of the lead-free methylammonium tin triiodide (CH3NH3SnI3) perovskite films in a solution growth process Highly uniform, pinhole-free perovskite films are obtained from a dimethyl sulfoxide (DMSO) solution via a transitional SnI2·3DMSO intermediate phase This high-quality perovskite film enables the realization of heterojunction depleted solar cells based on mesoporous TiO2 layer but in the absence of any hole-transporting material with an unprecedented photocurrent up to 21 mA cm–2 Charge extraction and transient photovoltage decay measurements reveal high carrier densities in the CH3NH3SnI3 perovskite device which are one order of magnitude larger than CH3NH3PbI3-based devices but with comparable
540 citations
01 Jan 2015
500 citations
TL;DR: In this article, a room-temperature solvent-solvent extraction (SSE) method is used for the deposition of hybrid-perovskite thin films over large areas, and its versatility in depositing high quality thin films of controlled thicknesses and various compositions (CH3NH3PbI(3−x)Brx; x = 0, 1, 2, or 3) is demonstrated.
Abstract: The room-temperature solvent–solvent extraction (SSE) concept is used for the deposition of hybrid-perovskite thin films over large areas. In this simple process, perovskite precursor solution is spin-coated onto a substrate, and instead of the conventional thermal annealing treatment, the coated substrate is immediately immersed in a bath of another solvent at room temperature. This results in efficient extraction of the precursor-solvent and induces rapid crystallization of uniform, ultra-smooth perovskite thin films. The mechanisms involved in the SSE process are studied further, and its versatility in depositing high quality thin films of controlled thicknesses (20 to 700 nm) and various compositions (CH3NH3PbI(3−x)Brx; x = 0, 1, 2, or 3) is demonstrated. Planar perovskite solar cells (PSCs) based on SSE-deposited CH3NH3PbI3 perovskite thin films deliver power conversion efficiency (PCE) up to 15.2%, and most notably an average PCE of 10.1% for PSCs with sub-100 nm semi-transparent perovskite thin films. The SSE method has generic appeal, and its key attributes—room-temperature process, rapid crystallization, large-area uniform deposition, film-thickness control, ultra-smoothness, and compositional versatility—make the SSE method potentially suitable for roll-to-roll scalable processing of hybrid-perovskite thin films for future multifunctional PSCs.
379 citations
TL;DR: The present study gives a reproductive and facile strategy toward high quality of perovskite thin films and efficient solar cells by controlling DMSO species in the complex-precursor system (CPS).
Abstract: The highly developed crystallization process with respect to perovskite thin films is favorable for efficient solar cells. Here, an innovative intermolecular self-assembly approach was employed to retard the crystallization of PbI2 in dimethylformamide (DMF) by additional solvent of dimethyl sulfoxide (DMSO), which was proved to be capable of coordinating with PbI2 by coordinate covalent bond. The obtained PbI2(DMSO)x (0 ≤ x ≤ 1.86) complexes tend to be closely packed by means of intermolecular self-assembly. Afterward, an intramolecular exchange of DMSO with CH3NH3I (MAI) enabled the complexes to deform their shape and finally to reorganize to be an ultraflat and dense thin film of CH3NH3PbI3. The controllable grain morphology of perovskite thin film allows obtaining a power conversion efficiency (PCE) above 17% and a stabilized power output above 16% within 240 s by controlling DMSO species in the complex–precursor system (CPS). The present study gives a reproductive and facile strategy toward high qual...
342 citations
TL;DR: The retrograde solubility of various hybrid perovskites through the correct choice of solvent(s) is shown and their solubilities curves are reported.
327 citations
TL;DR: In this paper, an improved CH3NH3PbI3−xClx perovskite quality is demonstrated with good crystallization and stability by using water as an additive during crystal perovsite growth.
Abstract: A key issue for perovskite solar cells is the stability of perovskite materials due to moisture effects under ambient conditions, although their efficiency is improved constantly. Herein, an improved CH3NH3PbI3−xClx perovskite quality is demonstrated with good crystallization and stability by using water as an additive during crystal perovskite growth. Incorporating suitable water additives in N,N-dimethylformamide (DMF) leads to controllable growth of perovskites due to the lower boiling point and the higher vapor pressure of water compared with DMF. In addition, CH3NH3PbI3−xClx · nH2O hydrated perovskites, which can be resistant to the corrosion by water molecules to some extent, are assumed to be generated during the annealing process. Accordingly, water additive based perovskite solar cells present a high power conversion efficiency of 16.06% and improved cell stability under ambient conditions compared with the references. The findings in this work provide a route to control the growth of crystal perovskites and a clue to improve the stability of organic–inorganic halide perovskites.
322 citations
TL;DR: In situ X-ray scattering data is used to study isothermal transformations of perovskite films derived from chloride, iodide, nitrate, and acetate lead salts and suggests that careful choice of the lead salt will aid in controlling crystal growth, leading to superior films and better performing solar cells.
Abstract: Methylammonium lead halide perovskite solar cells continue to excite the research community due to their rapidly increasing performance which, in large part, is due to improvements in film morphology. The next step in this progression is control of the crystal morphology which requires a better fundamental understanding of the crystal growth. In this study we use in situ X-ray scattering data to study isothermal transformations of perovskite films derived from chloride, iodide, nitrate, and acetate lead salts. Using established models we determine the activation energy for crystallization and find that it changes as a function of the lead salt. Further analysis enabled determination of the precursor composition and showed that the primary step in perovskite formation is removal of excess organic salt from the precursor. This understanding suggests that careful choice of the lead salt will aid in controlling crystal growth, leading to superior films and better performing solar cells.
318 citations
TL;DR: In this article, a triplet-involved relaxation of delayed fluorescence (DF) and phosphorescence is activated in a group of pure organic aromatic acids and esters at ambient conditions.
Abstract: Pure organic materials exhibiting room temperature phosphorescence (RTP) have significant fundamental importance and promising optoelectronic and biological applications. Exploration of metal- and heavy atom-free pure organic phosphors, however, remains challenging because achieving emissive triplet relaxation that outcompetes the vibrational loss is difficult without metal or heavy atoms. In this contribution, in contrast to aggregation-caused quenching (ACQ) normally observed in conventional chromophores, a unique phenomenon of crystallization-induced dual emission (CIDE), namely, simultaneously boosted fluorescence and phosphorescence upon crystallization, is observed in a group of pure organic aromatic acids and esters at ambient conditions. Moreover, two triplet-involved relaxations of delayed fluorescence (DF) and phosphorescence are activated. Such efficient intrinsic emission from both singlet and triplet states in a single compound without employing metal or heavy atoms is suitable for a variety of fundamental research and applications.
282 citations
TL;DR: Thermal stability of hybrid solar cells containing spiro-OMeTAD as hole-transporting layer is investigated and suppression of the crystal growth in the holes is demonstrated to be a viable tactic to achieve a significant increase in the solar cell resistance to thermal stress and improve the overall lifetime of the device.
Abstract: Thermal stability of hybrid solar cells containing spiro-OMeTAD as hole-transporting layer is investigated. It is demonstrated that fully symmetrical spiro-OMeTAD is prone to crystallization, and growth of large crystalline domains in the hole-transporting layer is one of the causes of solar cell degradation at elevated temperatures, as crystallization of the material inside the pores or on the interface affects the contact between the absorber and the hole transport. Suppression of the crystal growth in the hole-transporting layer is demonstrated to be a viable tactic to achieve a significant increase in the solar cell resistance to thermal stress and improve the overall lifetime of the device. Findings described in this publication could be applicable to hybrid solar cell research as a number of well-performing architectures rely heavily upon doped spiro-OMeTAD as hole-transporting material.
TL;DR: This research presents a new generation of high-performance liquid chromatography platforms for high-resolution 3D image analysis that combines sorption, desorption, and recovery of Na6(CO3)(SO4)2, which was developed at the Lawrence Berkeley National Laboratory.
Abstract: C. M. Palumbiny, Prof. P. Müller-Buschbaum Lehrstuhl für Funktionelle Materialien Physik-Department Technische Universität München James-Franck-Str. , 1, 85748 Garching , Germany E-mail: muellerb@ph.tum.de Dr. F. Liu, Prof. T. P. Russell Department of Polymer Science and Engineering University of Massachusetts Amherst 120 Governors Drive , Amherst , MA 01003 , USA Dr. F. Liu, Prof. T. P. Russell Materials Sciences Division Lawrence Berkeley National Laboratory 1 Cyclotron Road , Berkeley , CA 94720 , USA Dr. A. Hexemer, Dr. C. Wang Advanced Light Source Lawrence Berkeley National Laboratory 1 Cyclotron Road Berkeley , CA 94720 , USA
TL;DR: Etching tests on these ZIFs reveal that etching occurs preferentially in the crystallographic directions richer in metal-ligand bonds; that, along these directions, the etching rate tends to be faster on the crystal surfaces of higher dimensionality; and that the etch can be modulated by adjusting the pH of the etchant solution.
Abstract: Controlling the shape of metal-organic framework (MOF) crystals is important for understanding their crystallization and useful for myriad applications. However, despite the many advances in shaping of inorganic nanoparticles, post-synthetic shape control of MOFs and, in general, molecular crystals remains embryonic. Herein, we report using a simple wet-chemistry process at room temperature to control the anisotropic etching of colloidal ZIF-8 and ZIF-67 crystals. Our work enables uniform reshaping of these porous materials into unprecedented morphologies, including cubic and tetrahedral crystals, and even hollow boxes, by an acid-base reaction and subsequent sequestration of leached metal ions. Etching tests on these ZIFs reveal that etching occurs preferentially in the crystallographic directions richer in metal-ligand bonds; that, along these directions, the etching rate tends to be faster on the crystal surfaces of higher dimensionality; and that the etching can be modulated by adjusting the pH of the etchant solution.
TL;DR: DNA-coated colloids that can rearrange and anneal are reported, thus enabling the growth of large colloidal crystals from a wide range of micrometre-sized DNA-coating colloids for the first time.
Abstract: DNA-coated colloids hold great promise for self-assembly of programmed heterogeneous microstructures, provided they not only bind when cooled below their melting temperature, but also rearrange so that aggregated particles can anneal into the structure that minimizes the free energy. Unfortunately, DNA-coated colloids generally collide and stick forming kinetically arrested random aggregates when the thickness of the DNA coating is much smaller than the particles. Here we report DNA-coated colloids that can rearrange and anneal, thus enabling the growth of large colloidal crystals from a wide range of micrometre-sized DNA-coated colloids for the first time. The kinetics of aggregation, crystallization and defect formation are followed in real time. The crystallization rate exhibits the familiar maximum for intermediate temperature quenches observed in metallic alloys, but over a temperature range smaller by two orders of magnitude, owing to the highly temperature-sensitive diffusion between aggregated DNA-coated colloids.
TL;DR: In this paper, the thermal conductivity and thermal diffusivity of the solid/liquid phase change linear n-alkanes were measured simultaneously by the transient multi-current hot wire technique at atmospheric pressure in the range 258-348 K. The same set-up was used to measure the liquid and the solid states at different electrical currents.
TL;DR: The results suggest that the porosity and network structure of CNCSFD agglomerates contribute significantly to good dispersion of C NC in the PLA matrix.
TL;DR: In this paper, the authors used synchrotron wide-angle X-ray diffraction (WAXD) measurements, and observed that strain-induced crystallization of NR/ZDMA composites had a direct affect on the ultimate mechanical properties.
Abstract: Natural rubber (NR) reinforced by in situ polymerization of zinc dimethacrylate (ZDMA) exhibits excellent mechanical properties. However, the corresponding reinforcement mechanism is still unclear. Using synchrotron wide-angle X-ray diffraction (WAXD) measurements, we observed that strain-induced crystallization of NR/ZDMA composites had a direct affect on the ultimate mechanical properties. An increase in ZDMA fraction resulted in a lower strain at the onset of crystallization. Further analysis revealed that three factors contributed to the reduction in onset strain, including higher whole cross-linking density due to the emergence of ionic cross-linking clusters, strain amplification of nanodispersion of poly-ZDMA (PZDMA), and the confinement effect of the filler network. The results of dynamic Monte Carlo simulation showed that the confinement effect of the filler network on chain segments favored segmental orientation in regions near the polymer–filler interface, thus inducing a decline in onset strain.
TL;DR: In this paper, high angular resolution synchrotron radiation diffraction measurements, realized operando on sodium batteries upon charge, reveal an extremely interesting phase diagram, created by the successive crystallization of four intermediate phases before the end composition NaV2(PO4)2F3 is reached.
Abstract: Na3V2(PO4)2F3 is a positive electrode material for Na-ion batteries which is attracting strong interest due to its high capacity, rate capability, and long-term cycling stability. The sodium extraction mechanism from this material has been always described in the literature as a straightforward solid solution, but several hints point toward a more complicated phase diagram. In this work we performed high angular resolution synchrotron radiation diffraction measurements, realized operando on sodium batteries upon charge. We reveal an extremely interesting phase diagram, created by the successive crystallization of four intermediate phases before the end composition NaV2(PO4)2F3 is reached. Only one of these phases undergoes a solid solution reaction, in the interval between 1.8 and 1.3 Na per formula unit. The ability to resolve weak Bragg reflections allowed us to reveal differences in terms of symmetry among the phases, to determine their previously unknown space groups, and to correlate them with sodium...
TL;DR: Pressure-dependent stability calculations suggested high pressure as a means to bring polymorphs into existence, and one of them could indeed be crystallized in the 0.02 to 0.50 GPa pressure range and was found to be metastable at ambient pressure, effectively derisking the appearance of a more stable polymorph during late-stage development of Dalcetrapib.
Abstract: Organic molecules, such as pharmaceuticals, agro-chemicals and pigments, frequently form several crystal polymorphs with different physicochemical properties. Finding polymorphs has long been a purely experimental game of trial-and-error. Here we utilize in silico polymorph screening in combination with rationally planned crystallization experiments to study the polymorphism of the pharmaceutical compound Dalcetrapib, with 10 torsional degrees of freedom one of the most flexible molecules ever studied computationally. The experimental crystal polymorphs are found at the bottom of the calculated lattice energy landscape, and two predicted structures are identified as candidates for a missing, thermodynamically more stable polymorph. Pressure-dependent stability calculations suggested high pressure as a means to bring these polymorphs into existence. Subsequently, one of them could indeed be crystallized in the 0.02 to 0.50 GPa pressure range and was found to be metastable at ambient pressure, effectively derisking the appearance of a more stable polymorph during late-stage development of Dalcetrapib.
TL;DR: This work shows that SSZ-13 grows by two concerted mechanisms: nonclassical growth involving the attachment of amorphous aluminosilicate particles to crystal surfaces and classical layer-by-layer growth via the incorporation of molecules to advancing steps on the crystal surface.
Abstract: Many synthetic and natural crystalline materials are either known or postulated to grow via nonclassical pathways involving the initial self-assembly of precursors that serve as putative growth units for crystallization. Elucidating the pathway(s) by which precursors attach to crystal surfaces and structurally rearrange (postattachment) to incorporate into the underlying crystalline lattice is an active and expanding area of research comprising many unanswered fundamental questions. Here, we examine the crystallization of SSZ-13, which is an aluminosilicate zeolite that possesses exceptional physicochemical properties for applications in separations and catalysis (e.g., methanol upgrading to chemicals and the environmental remediation of NO(x)). We show that SSZ-13 grows by two concerted mechanisms: nonclassical growth involving the attachment of amorphous aluminosilicate particles to crystal surfaces and classical layer-by-layer growth via the incorporation of molecules to advancing steps on the crystal surface. A facile, commercially viable method of tailoring SSZ-13 crystal size and morphology is introduced wherein growth modifiers are used to mediate precursor aggregation and attachment to crystal surfaces. We demonstrate that small quantities of polymers can be used to tune crystal size over 3 orders of magnitude (0.1-20 μm), alter crystal shape, and introduce mesoporosity. Given the ubiquitous presence of amorphous precursors in a wide variety of microporous crystals, insight of the SSZ-13 growth mechanism may prove to be broadly applicable to other materials. Moreover, the ability to selectively tailor the physical properties of SSZ-13 crystals through molecular design offers new routes to optimize their performance in a wide range of commercial applications.
TL;DR: It is found that the crystal formation is kinetically driven by the annealing atmosphere, time and temperature, which indicates a critical impact of the atmosphere upon crystallization and the ultimate device performance.
Abstract: Recently, solution-processable organic–inorganic metal halide perovskites have come to the fore as a result of their high power-conversion efficiencies (PCE) in photovoltaics, exceeding 17%. To attain reproducibility in the performance, one of the critical factors is the processing conditions of the perovskite film, which directly influences the photophysical properties and hence the device performance. Here we study the effect of annealing parameters on the crystal structure of the perovskite films and correlate these changes with its photophysical properties. We find that the crystal formation is kinetically driven by the annealing atmosphere, time and temperature. Annealing in air produces an improved crystallinity and large grain domains as compared to nitrogen. Lower photoluminescence quantum efficiency (PLQE) and shorter photoluminescence (PL) lifetimes are observed for nitrogen annealed perovskite films as compared to the air-annealed counterparts. We note that the limiting nonradiative pathways (i...
TL;DR: In this paper, UiO-66 with crystal size ranging from hundreds of nanometers to a few micrometers and with cubic and cuboctahedral morphologies were synthesized.
Abstract: UiO-66 with crystal size ranging from hundreds of nanometers to a few micrometers and with cubic and cuboctahedral morphologies were synthesized. Crystal size and morphology varied with the additive amount of hydrofluoric acid and the concentration of reactants (ZrCl4 and H2BDC) during solvothermal synthesis. According to energy dispersive spectrometry (EDS) and 19F MAS NMR measurements, the fluorine ions directly bonded to Zr in the SBUs (secondary building units) in the MOF framework due to their strongest electronegativity. The bonding of the fluorine ions and Zr not only compensated for the charge imbalance of the framework caused by missing linkers but also competed with the linkers to coordinate with the Zr metal centers, thereby controlling the processes of nucleation and growth of the UiO-66 crystals. The samples were further characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and Ar sorption isotherms, showing that the introduction of fluorine enhanced the thermostability and porosity of UiO-66.
TL;DR: The results show that the patterns of the resulting salt crystal stains are mainly governed by wetting properties of the emerging crystal as well as the pathway of nucleation and growth, and are independent of the evaporation rate and thermal conductivity of the substrates.
Abstract: The study of the behavior of sessile droplets on solid substrates is not only associated with common everyday phenomena, such as the coffee stain effect, limescale deposits on our bathroom walls , but also very important in many applications such as purification of pharmaceuticals, de-icing of airplanes, inkjet printing and coating applications. In many of these processes, a phase change happens within the drop because of solvent evaporation, temperature changes or chemical reactions, which consequently lead to liquid to solid transitions in the droplets. Here we show that crystallization patterns of evaporating of water drops containing dissolved salts are different from the stains reported for evaporating colloidal suspensions. This happens because during the solvent evaporation, the salts crystallize and grow during the drying. Our results show that the patterns of the resulting salt crystal stains are mainly governed by wetting properties of the emerging crystal as well as the pathway of nucleation and growth, and are independent of the evaporation rate and thermal conductivity of the substrates.
TL;DR: A series of solvents with different solubilities for DR3TBDTT and PC71 BM, and different boiling points, is used for solvent vapor annealing (SVA) treatment to systematically investigate the solvent-morphology-performance relationship.
Abstract: A series of solvents with different solubilities for DR3TBDTT and PC71 BM, and different boiling points, is used for solvent vapor annealing (SVA) treatment to systematically investigate the solvent-morphology-performance relationship. The presence of solvent molecules inside bulk-heterojunction (BHJ) thin films promotes the mobility of both donor and acceptor molecules, leading to crystallization and aggregation, which are important in modulating morphology.
TL;DR: In this article, an anti-solvent assisted crystallization (ASAC) approach was used to synthesize crystalline CH 3 NH 3 PbBr 3 thin films with uniform microstructures through accelerated crystallization process at room temperature.
TL;DR: In this paper, the microcellular structure and crystallization behavior of polylactide composite foams were characterized using scanning electron microscopy and differential scanning calorimetry, and the results showed that the presence of nanoclay and talc together with the expedited crystallization enhanced the PLA foams morphology with a finer and more uniform cell structure.
TL;DR: In this paper, the upconversion luminescence of the glass ceramic co-doped with Yb 3+ and Er 3+ is about 60 times as high as that of the precursor glass, attributing to the modification of Yb3+ /Er 3+ surrounding from phase-separated amorphous nanoparticle to β-NaGdF 4 crystalline lattice with low phonon energy and high crystallinity after crystallization.
TL;DR: Predominantly biobased products were shown to have dramatically improved crystallization kinetics, mechanical properties, melt elasticity and strength, and foaming-ability compared with PLA, and the microfibrillar blends were produced using an environmentally friendly and cost-effective process.
TL;DR: It is shown that the co-existence of In( 3+) and Cr(3+) induces a rapid crystal growth of large single crystals of heterometallic In-Cr-MOPs with the [M8L12] (M=In/Cr, L=dinegative 4,5-imidazole-dicarboxylate) cubane-like structure, which exhibit an exceptionally high proton conductivity.
Abstract: Metal–organic polyhedra (MOPs) or frameworks (MOFs) based on Cr3+ are notoriously difficult to synthesize, especially as crystals large enough to be suitable for characterization of the structure or properties. It is now shown that the co-existence of In3+ and Cr3+ induces a rapid crystal growth of large single crystals of heterometallic In-Cr-MOPs with the [M8L12] (M=In/Cr, L=dinegative 4,5-imidazole-dicarboxylate) cubane-like structure. With a high concentration of protons from 12 carboxyl groups decorating every edge of the cube and an extensive H-bonded network between cubes and surrounding H2O molecules, the newly synthesized In-Cr-MOPs exhibit an exceptionally high proton conductivity (up to 5.8×10−2 S cm−1 at 22.5 °C and 98 % relative humidity, single crystal).
TL;DR: In this paper, a monoclinic structure of the Cu2SnS3 thin film was obtained by crystallization in a sulfur/tin mixing atmosphere from stacked NaF/Cu/Sn precursors deposited by sequential evaporation of Sn, Cu elements, and NaF.
Abstract: Cu2SnS3 thin films were prepared by crystallization in a sulfur/tin mixing atmosphere from stacked NaF/Cu/Sn precursors deposited by the sequential evaporation of Sn, Cu elements, and NaF. The NaF mole ratio was changed at (x = 0 to 0.12). From X-ray diffraction patterns and Raman spectra, the Cu2SnS3 thin films were considered to have a monoclinic structure. The grain size of the Cu2SnS3 thin films decreased with increasing NaF/Cu mole ratio. The band-gap energies of the Cu2SnS3 thin films determined from quantum efficiency spectra were 0.93 and 1.02 eV. The solar cell with x = 0.075 demonstrated the best performance, namely, Voc = 283 mV, Isc = 37.3 mA/cm2, FF = 0.439, and ? = 4.63%.