Name: solution-processed "silver-bismuth-iodine" ternary thin films for lead-free photovoltaic absorbers
Uploaded: 2018-09-27T14:45:00
Description: Watch this Scientific Journal Video about Solution-Processed "Silver-Bismuth-Iodine" Ternary Thin Films for Lead-Free Photovoltaic Absorbers at JoVE.com

This work was supported by the Daegu Gyeongbuk Institute of Science and Technology (DGIST) Research and Development (R&#38;D) Programs of the Ministry of Science, ICT and Future Planning of Korea (18-ET-01).&#160;This work was also supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP) and the Ministry of Trade, Industry &#38; Energy(MOTIE) of the Republic of Korea (No. 20173010013200).

1. Preparation of Bare-glass, Fluorine-doped Tin Oxide (SnO2:F) Substrates
<ol>
	<li>To clean the bare-glass, fluorine-doped tin oxide (FTO) substrates, sonicate them sequentially in an aqueous solution containing 2% Triton, deionized (DI) water, acetone, and isopropyl alcohol (IPA), each for 15 min.</li>
	<li>Put the cleaned substrates in the heating oven at 70 &#176;C for 1 h to remove the residual IPA.</li>
</ol>
2. Preparation of Compact TiO2 Layers (c-TiO2) to...

<ol>
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H., Palazzi, M., Rivet, J., Flahaut, J., C&#233;olin, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Etude+du+Systeme+AgIBiI3.">Etude du Systeme AgIBiI3.</a> Materials Research Bulletin. 14 (3), 325-328 (1979).</li><li>Kondo, S., Itoh, T., Saito, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strongly+Enhanced+Optical+Absorption+in+Quench-Deposited+Amorphous+AgI+Films.">Strongly Enhanced Optical Absorption in Quench-Deposited Amorphous AgI Films.</a> Physical Review B. 57 (20), 13235-13240 (1998).</li><li>Kumar, P. S., Dayal, P. B., Sunandana, C. 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H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Mono-+versus+Di-ammonium+Cation+of+2,2'-Bithiophene+Derivatives+on+the+Structure+of+Organic-Inorganic+Hybrid+Materials+Based+on+Iodo+Metallates.">Effect of Mono- versus Di-ammonium Cation of 2,2'-Bithiophene Derivatives on the Structure of Organic-Inorganic Hybrid Materials Based on Iodo Metallates.</a> Inorganic Chemistry. 42 (17), 5330-5339 (2003).</li><li>Zhu, H., Pan, M., Johansson, M. B., Johansson, E. M. 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We have provided a detailed protocol for the solution fabrication of Ag-Bi-I ternary semiconductors, which are to be exploited as lead-free photovoltaic absorbers in thin-film solar cells with mesoscopic device architectures. c-TiO2 layers were formed on FTO substrates to avoid electron leakage flowing into the FTO electrodes. m-TiO2 layers were sequentially formed on c-TiO2-coated FTO substrates to improve the electron extractions generated from the photovoltaic absorbers (i.e.,...

Solution-processed inorganic thin-film solar cells have been widely studied by many researchers seeking to convert sunlight directly into electricity1,2,3,4,5. With the development of material synthesis and device architecture, lead halide-based perovskites have been reported to be the best solar cell absorbers with a power conversion efficiency (PCE) greater than 22%5. However, there are growing concerns about the use of toxic lead, as well as stability issues of lead-halide perovskite itself.
It has recently been reported that bismuth-based hybrid perovskites can be formed by incorporating monovalent cations into a bismuth iodide complex unit and that these can be used as photovoltaic absorbers in mesoscopic solar cell architectures6,7,8. The lead in the perovskites can be replaced with bismuth, which has the 6s2 outer lone pair; however, so far only conventional lead halide methodologies have been used for bismuth-based hybrid perovskites with complex crystal structures, despite the fact that they have different oxidation states and chemical properties9. In addition, these perovskites have poor surface morphologies and produce relatively thick films in the context of thin-film device applications; therefore, they have a poor photovoltaic performance with high band-gap energy (&#62; 2 eV)6,7,8. Thus, we sought to find a new method to produce bismuth-based thin-film semiconductors, which are environmentally friendly, air-stable, and have low band-gap energy (&#60; 2 eV), considering the material design and methodology.
We present solution-processed Ag-Bi-I ternary thin films, which can be crystallized to AgBi2I7 and Ag2BiI5, for lead-free and air-stable semiconductors10,11. In this study for the AgBi2I7 composition, n-butylamine is used as a solvent to simultaneously dissolve the silver iodide (AgI) and bismuth iodide (BiI3) precursors. The mixture is spin-cast and annealed at 150 &#176;C for 30 min in an N2-filled glove box; subsequently, the films are quenched to room temperature. The resultant thin films are brown-black in color. In addition, the surface morphology and crystal composition of the Ag-Bi-I ternary systems are controlled by the annealing temperatures and precursor ratio of AgI/BiI3. The resulting AgBi2I7 thin films exhibit a cubic phase crystalline structure, dense and smooth surface morphologies with large grains of 200 - 800 nm in size, and an optical band gap of 1.87 eV starting to absorb light from a wavelength of 740 nm. It has recently been reported that by optimizing the crystal compositions and device architecture, Ag-Bi-I ternary thin-film solar cells can achieve a PCE of 4.3%.

<table>
	<tbody>
		<tr>
			<td>Bismuth(III) iodide, Puratronic, 99.999% (metals basis)</td>
			<td>Afa Aesar</td>
			<td>7787-64-6</td>
			<td>stored in N2-filled condition</td>
		</tr>
		<tr>
			<td>Silver iodide, Premion, 99.999% (metals basis)</td>
			<td>Afa Aesar</td>
			<td>7783-96-2</td>
			<td>stored in N2-filled condition</td>
		</tr>
		<tr>
			<td>Butylamine 99.5%</td>
			<td>Sigma-Aldrich</td>
			<td>109-73-9</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma-Aldrich</td>
			<td>9002-93-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Isopropyl alcohol (IPA)</td>
			<td>Duksan</td>
			<td>67-63-0</td>
			<td>Electric High Purity GRADE</td>
		</tr>
		<tr>
			<td>Titanium(IV) isopropoxide</td>
			<td>Sigma-Aldrich</td>
			<td>546-68-9</td>
			<td>&#8805;97.0%</td>
		</tr>
		<tr>
			<td>Ethyl alcohol</td>
			<td>Sigma-Aldrich</td>
			<td>64-17-5</td>
			<td>200 proof, ACS reagent, &#8805;99.5%</td>
		</tr>
		<tr>
			<td>Hydrochloric acid</td>
			<td>SAMCHUN</td>
			<td>7647-01-0</td>
			<td>Extra pure</td>
		</tr>
		<tr>
			<td>Titanium tetrachloride (TiCl4)</td>
			<td>sharechem</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>50nm-sized TiO2 nanoparticle paste</td>
			<td>sharechem</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>2-propanol</td>
			<td>Sigma-Aldrich</td>
			<td>67-63-0</td>
			<td>anhydrous, 99.5%</td>
		</tr>
		<tr>
			<td>Terpineol</td>
			<td>Merck</td>
			<td>8000-41-7</td>
			<td></td>
		</tr>
		<tr>
			<td>Heating oven</td>
			<td>WiseTherm</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Oxygen (O2) plasma</td>
			<td>AHTECH</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>X-ray diffraction (XRD)</td>
			<td>Rigaku</td>
			<td></td>
			<td>Rigaku Miniflex 600 diffractometer with a NaI scintillation counter and using monochromatized Cu-K&#945; radiation 
			(1.5406 &#197; wavelength).</td>
		</tr>
		<tr>
			<td>Fourier transform infrared (FTIR)</td>
			<td>Bruker</td>
			<td></td>
			<td>Bruker Tensor 27</td>
		</tr>
		<tr>
			<td>field-emission scanning electron microscope (FE-SEM)</td>
			<td>Hitachi</td>
			<td></td>
			<td>Hitachi SU8230</td>
		</tr>
		<tr>
			<td>UV-Vis spectra</td>
			<td>PerkinElmer</td>
			<td></td>
			<td>PerkinElmer LAMBDA 950 
			Spectrophotometer</td>
		</tr>
		<tr>
			<td>Ultraviolet photoelectron spectroscopy (UPS)</td>
			<td>RBD Instruments</td>
			<td></td>
			<td>PHI5500 Multi-Technique system</td>
		</tr>
	</tbody>
</table>

solution-processed "silver-bismuth-iodine" ternary thin films for lead-free photovoltaic absorbers

Bismuth-based hybrid perovskites are regarded as promising photo-active semiconductors for environment-friendly and air-stable solar cell applications. However, poor surface morphologies and relatively high bandgap energies have limited their potential. Silver-bismuth-iodine (Ag-Bi-I) is a promising semiconductor for optoelectronic devices. Therefore, we demonstrate the fabrication of Ag-Bi-I ternary thin films using material solution processing. The resulting thin films exhibit controlled surface morphologies and optical bandgaps according to their thermal annealing temperatures. In addition, it has been reported that Ag-Bi-I ternary systems crystallize to AgBi2I7, Ag2BiI5, etc. according to the ratio of the precursor chemicals. The solution-processed AgBi2I7 thin films exhibit a cubic-phase crystal structure, dense, pinhole-free surface morphologies with grains ranging in size from 200 to 800 nm, and an indirect bandgap of 1.87 eV. The resultant AgBi2I7 thin films show good air stability and energy band diagrams, as well as surface morphologies and optical bandgaps suitable for lead-free and air-stable single-junction solar cells. Very recently, a solar cell with 4.3% power conversion efficiency was obtained by optimizing the Ag-Bi-I crystal compositions and solar cell device architectures.

It has been reported that the Ag-Bi-I ternary systems, which are regarded as promising semiconductors, are crystallized in various compositions, such as AgBi2I7, AgBiI4, and Ag2BiI510, according to the molar ratio of AgI to BiI3. Earlier studies have shown that bulk crystal forms with various compositions of Ag-Bi-I ternary systems can be experimentally synthesized by changing the molar ratio of AgI ...

Watch this Scientific Journal Video about Solution-Processed "Silver-Bismuth-Iodine" Ternary Thin Films for Lead-Free Photovoltaic Absorbers at JoVE.com

Solution-Processed &quot;Silver-Bismuth-Iodine&quot; Ternary Thin Films for Lead-Free Photovoltaic Absorbers

Herein, we present detailed protocols for solution-processed silver-bismuth-iodine (Ag-Bi-I) ternary semiconductor thin films fabricated on TiO2-coated transparent electrodes and their potential application as air-stable and lead-free optoelectronic devices.

Solution-Processed "Silver-Bismuth-Iodine" Ternary Thin Films for Lead-Free Photovoltaic Absorbers

Bismuth-based hybrid perovskites are regarded as promising photo-active semiconductors for environment-friendly and air-stable solar cell applications. ...

This method can help you answer key questions about how to make solution-processable silver-bismuth-iodine ternary semiconductors for environmentally friendly thin film solar cells and adopt applications. The main advantage of this technique is the solution fabrication of silver-bismuth-iodine which is then used as a lead-free photovoltaic absorber in thin film solar cells with a microscopic device architectures. This technique has potential applications in the production of environmentally-friendly thin film solar cells because the silver-bismuth-iodine ternary semiconductors are lead-free, air-stable photovoltaic absorbers.To begin preparing the precursor solution for compact titanium dioxide layers, place 8 milliliters of anhydrous ethanol in a 20 milliliter glass vial and start stirring it vigorously. Add 0.74 milliliters of titanium isopropoxide to the stirring ethanol dropwise. And then rapidly add 0.06 milliliters of concentrated hydrochloric acid.Stir the mixture for between 12 and 24 hours at room temperature to form the precursor solution. Next, sonicate a bare one inch by one inch FTO substrate for 15 minutes each in 2%aqueous octoxynol-9, acetone, and isopropyl alcohol. Dry the clean substrate in an oven at 70 degrees Celsius for one hour and let it cool to room temperature in air.Then, fix the substrate on a spin coater chuck. Fill a 1 milliliter or 3 milliliter syringe with compact titanium dioxide layer precursor solution and attach a 0.2 nanometer syringe filter. Filter the solution into a small vial.Apply 200 microliters of the filtered precursor solution to the substrate to fully cover it. Spin coat the substrate at 3000 RPM for 30 seconds. Anneal the film in an oven at 500 degrees Celsius for one hour.Then turn off the heat and let the substrate cool in air to room temperature, which usually takes about six hours. Next, immerse the coated substrate in an aqueous 0.12 molar solution of titanium tetrachloride. Soak the substrate in a 70 degree Celsius oven for 30 minutes.Thoroughly rinse the substrate in deionized water afterwards to remove residual titanium tetrachloride. Anneal the film at 500 degrees Celsius for one hour and then allow it to cool to room temperature in air. Once cool, store the compact titanium dioxide-coated substrate under nitrogen gas for later use.To begin preparing the precursor solution for a mesoporous titanium dioxide nanoparticle layer in a 5 milliliter glass vial, combine 0.5 grams of 50 nanometer titanium dioxide nanoparticle paste with 1.75 grams of isopropyl alcohol and 0.5 grams of terpineol. Add a stir bar to the vial and stir until the paste has completely dissolved. This usually takes about one hour.Next, fix a compact titanium dioxide-coated FTO substrate on a spin coater and apply 200 microliters of the nanoparticle solution to the substrate surface. Spin coat the substrate at 5000 RPM for 30 seconds. Anneal the coated substrate in an oven at 500 degrees Celsius for one hour and allow it to cool to room temperature.Then soak the substrate in an aqueous 0.12 molar solution of titanium tetrachloride at 70 degrees Celsius for 30 minutes. Thoroughly rinse the substrate with deionized water. Anneal it at 500 degrees Celsius for one hour and let it cool to room temperature in air.Store the substrate coated with compact and mesoporous titanium dioxide layers under nitrogen gas for later use. To begin preparing thin films of the silver iodobismuthate, silver dibismuth heptaiodide, in a nitrogen-filled glovebox at low humidity combine 0.3 grams of bismuth-three iodide, 0.06 grams of silver iodide, and 3 milliliters of n-butylamine. Vigorously vortex the mixture until the solids have mostly dissolved, and then syringe filter the precursor solution through a 0.2 micrometer polytetrafluoroethylene filter.Next, fix the desired substrate on a spin coater and apply 200 microliters of the filtered precursor solution. Spin coat the substrate at 6000 RPM for 30 seconds. Place the substrate on a hot plate and heat it to 150 degrees Celsius.Anneal the film at that temperature for 30 minutes and then quickly remove it from the hot plate to quench it. In a nitrogen-filled glove box, combine 10 milligrams of P3HT and 1 milliliter of chlorobenzene. Stir the mixture at 50 degrees Celsius for 30 minutes to completely dissolve the P3HT and then filter the mixture with a 0.2 micrometer PTFE syringe filter.Next, fix an FTO substrate coated with silver dibismuth hepatiodide on compact and mesoporous titanium dioxide on a spin coater. Apply 100 microliters of the P3HT solution to the substrate and spin coat the substrate at 4000 RPM or 30 seconds. Anneal the P3HT film on a hot plate preheated to 130 degrees Celsius for 10 minutes.Let the substrate cool to room temperature in the glove box. Lastly, use a thermal evaporator to deposit 100 nanometers of gold at 0.5 angstroms per second on the substrate to form the top gold contacts of the solar cell. silver-bismuth-iodine ternary thin films, 1:2, 1:1, and 2:1 molar ratios of silver iodide to bismuth-3 iodide were fabricated with this method.The 1:2 film showed a single peak at about 42 degrees, indiciating a cubic structure. Peak splitting was observed for the 1:1 and 2:1 films, indicating a hexagonal structure. The 1:2 film absorbed longer wavelengths than the 2:1 film did.Further, the 1:2 film had a smooth surface with large grains whereas particles of excess silver iodide were observed on the 2:1 film. The 1:2 film was thus chosen for further study. X-ray diffraction indicated that an annealing temperature of 150 degrees Celsius was required for the 1:2 film to crystallize entirely in the cubic phase.The film was stable in the air for at least 10 days. FTIR spectroscopies suggested that residual n-butylamine remained weakly complexed to bismuth-3 iodide and silver iodide at lower annealing temperatures, suppressing the formation of silver-bismuth-iodine building blocks. The grains became larger and more densely packed as the annealing temperature increased.Films annealed at 150 degrees Celsius also had the most suitable absorption properties for use in solar cells. Overall, the silver dibismuth heptaiodide film annealed at 150 degrees Celsius showed suitable energetic properties for solar cell use. This technique paves the way for researchers of solution-processable thin film solar cells to further develop methodologies for silver-bismuth-iodine ternary semiconductors in applications such as lead-free and air-stable thin film solar cells.While attempting this procedure, you may want to use controlled humidity of under 20%for spin coating the substrate with the silver-bismuth-iodine precursor solution. If you spin coat the precursor solution at or above 30%humidity, you will see yellowish because of the highly reactive and photo If you cannot control the humidity in the spin coater, you can spin coat the precursor solution in a N-filled glove box. However, please keep in mind that you must completely purge the glove box after it's done.

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Research

JoVE Journal

Chemistry

Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and lignin. Layer-by-layer (LbL) assembly process which relies on the assembly of oppositely charged molecules from aqueous solutions was used to build a freestanding composite film of isolated wood polymers of lignin and oxidized nanofibril cellulose (NFC). To facilitate the assembly of these negatively charged polymers, a positively charged polyelectrolyte, poly(diallyldimethylammomium chloride) (PDDA), was used as a linking layer to create this simplified model cell wall. The layered adsorption process was studied quantitatively using quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry. The results showed that layer mass/thickness per adsorbed layer increased as a function of total number of layers. The surface coverage of the adsorbed layers was studied with atomic force microscopy (AFM). Complete coverage of the surface with lignin in all the deposition cycles was found for the system, however, surface coverage by NFC increased with the number of layers. The adsorption process was carried out for 250 cycles (500 bilayers) on a cellulose acetate (CA) substrate. Transparent free-standing LBL assembled nanocomposite films were obtained when the CA substrate was later dissolved in acetone. Scanning electron microscopy (SEM) of the fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle (PDDA-Lignin-PDDA-NC) was estimated to be 17 nm for two different lignin types used in the study. The data indicates a film with highly controlled architecture where nanocellulose and lignin are spatially deposited on the nanoscale (a polymer-polymer nanocomposites), similar to what is observed in the native cell wall.

The objective of this research was to form synthetic plant cell wall tissue using layer-by-layer assembly of nanocellulose fibrils and isolated lignin assembled from dilute aqueous suspensions.&#160; Surface measurement techniques of quartz crystal microbalance and atomic force microscopy were used to monitor the formation of the polymer-polymer nanocomposite material.

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and ...

Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO3 (001) and DyScO3 (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca2Nb3O10- nanosheets were used, prepared by delamination of their layered parent compound HCa2Nb3O10. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material.

Various procedures are outlined to prepare atomically defined templates for epitaxial growth of complex oxide thin films. Chemical treatments of single crystalline SrTiO3 (001) and DyScO3 (110) substrates were performed to obtain atomically smooth, single terminated surfaces. Ca2 Nb3 O10- nanosheets were used to create atomically defined templates on arbitrary substrates.

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain ...

Fabrication of Large-area Free-standing Ultrathin Polymer Films

This procedure describes a method for the fabrication of large-area and ultrathin free-standing polymer films. Typically, ultrathin films are prepared using either sacrificial layers, which may damage the film or affect its mechanical properties, or they are made on freshly cleaved mica, a substrate that is difficult to scale. Further, the size of ultrathin film is typically limited to a few square millimeters. In this method, we modify a surface with a polyelectrolyte that alters the strength of adhesion between polymer and deposition substrate. The polyelectrolyte can be shown to remain on the wafer using spectroscopy, and a treated wafer can be used to produce multiple films, indicating that at best minimal amounts of the polyelectrolyte are added to the film. The process has thus far been shown to be limited in scalability only by the size of the coating equipment, and is expected to be readily scalable to industrial processes. In this study, the protocol for making the solutions, preparing the deposition surface, and producing the films is described.

We describe a method for the fabrication of large-area (up to 13 cm diameter) and ultrathin (as thin as 8 nm) polymer films. Instead of using a sacrificial interlayer to delaminate the film from its substrate, we use a self-limiting surface treatment suitable for arbitrarily large areas.

This procedure describes a method for the fabrication of large-area and ultrathin free-standing polymer films.  Typically, ultrathin films are prepared ...

Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates

Functions of clusters in nano or sub-nano scale significantly depend on not only kinds of their components but also arrangements, or symmetry, of their components. Therefore, the arrangements in the clusters have been precisely characterized, especially for metal complexes. Contrary to this, characterizations of molecular arrangements in supramolecular clusters composed of organic molecules are limited to a few cases. This is because construction of the supramolecular clusters, especially obtaining a series of the supramolecular clusters, is difficult due to low stability of non-covalent bonds compare to covalent bonds. From this viewpoint, utilization of organic salts is one of the most useful strategies. A series of the supramolecules could be constructed by combinations of a specific organic molecule with various counter ions. Especially, primary ammonium carboxylates are suitable as typical examples of supramolecules because various kinds of carboxylic acids and primary amines are commercially available, and it is easy to change their combinations. Previously, it was demonstrated that primary ammonium triphenylacetates using various kinds of primary amines specifically construct supramolecular clusters, which are composed of four ammoniums and four triphenylacetates assembled by charge-assisted hydrogen bonds, in crystals obtained from non-polar solvents. This study demonstrates an application of the specific construction of the supramolecular clusters as a strategy to conduct systematical symmetric study for clarification of correlations between molecular arrangements in supramolecules and kinds and numbers of their components. In the same way with binary salts composed of triphenylacetates and one kind of primary ammoniums, ternary organic salts composed of triphenylacetates and two kinds of ammoniums construct the supramolecular clusters, affording a series of the supramolecular clusters with various kinds and numbers of the components.

This article describes construction of a series of hydrogen-bonding supramolecular clusters in crystals using primary ammonium triphenylacetates, which are recrystallized from non-polar solvents. This selective construction of the supramolecular clusters leads to effective systematical symmetric studies about a correlation between the supramolecular clusters and their components.

Functions of clusters in nano or sub-nano scale significantly depend on not only kinds of their components but also arrangements, or symmetry, of their ...

Cooling Rate Dependent Ellipsometry Measurements to Determine the Dynamics of Thin Glassy Films

This report aims to fully describe the experimental technique of using ellipsometry for cooling rate dependent Tg (CR-Tg) experiments. These measurements are simple high-throughput characterization experiments, which can determine the glass transition temperature (Tg), average dynamics, fragility and the expansion coefficient of the super-cooled liquid and glassy states for a variety of glassy materials. This technique allows for these parameters to be measured in a single experiment, while other methods must combine a variety of different techniques to investigate all of these properties. Measurements of dynamics close to Tg are particularly challenging. The advantage of cooling rate dependent Tg measurements over other methods which directly probe bulk and surface relaxation dynamics is that they are relatively quick and simple experiments, which do not utilize fluorophores or other complicated experimental techniques. Furthermore, this technique probes the average dynamics of technologically relevant thin films in temperature and relaxation time (&#964;&#945;) regimes relevant to the glass transition (&#964;&#945; &#62; 100 sec). The limitation to using ellipsometry for cooling rate dependent Tg experiments is that it cannot probe relaxation times relevant to measurements of viscosity (&#964;&#945; &#60;&#60; 1 sec). Other cooling rate dependent Tg measurement techniques, however, can extend the CR-Tg method to faster relaxation times. Furthermore, this technique can be used for any glassy system so long as the integrity of the film remains throughout the experiment.

Here, we present a protocol for cooling rate dependent ellipsometry experiments, which can determine the glass transition temperature (Tg), average dynamics, fragility and the expansion coefficient of the super-cooled liquid and glass for a variety of glassy materials.

This report aims to fully describe the experimental technique of using ellipsometry for cooling rate dependent Tg (CR-Tg) experiments. These measurements ...

Capillary Electrophoresis to Monitor Peptide Grafting onto Chitosan Films in Real Time

Free-solution capillary electrophoresis (CE) separates analytes, generally charged compounds in solution through the application of an electric field. Compared to other analytical separation techniques, such as chromatography, CE is cheap, robust and effectively requires no sample preparation (for a number of complex natural matrices or polymeric samples). CE is fast and can be used to follow the evolution of mixtures in real time (e.g., chemical reaction kinetics), as the signals observed for the separated compounds are directly proportional to their quantity in solution.
Here, the efficiency of CE is demonstrated for monitoring the covalent grafting of peptides onto chitosan films for subsequent biomedical applications. Chitosan&#39;s antimicrobial and biocompatible properties make it an attractive material for biomedical applications such as cell growth substrates. Covalently grafting the peptide RGDS (arginine - glycine - aspartic acid - serine) onto the surface of chitosan films aims at improving cell attachment. Historically, chromatography and amino acid analysis have been used to provide a direct measurement of the amount of grafted peptide. However, the fast separation and absence of sample preparation provided by CE enables equally accurate yet real-time monitoring of the peptide grafting process. CE is able to separate and quantify the different components of the reaction mixture: the (non-grafted) peptide and the chemical coupling agents. In this way the use of CE results in improved films for downstream applications.
The chitosan films were characterized through solid-state NMR (nuclear magnetic resonance) spectroscopy. This technique is more time-consuming and cannot be applied in real time, but yields a direct measurement of the peptide and thus validates the CE technique.

Free solution capillary electrophoresis is a fast, cheap and robust analytical method that enables the quantitative monitoring of chemical reactions in real time. Its utility for rapid, convenient and precise analysis is demonstrated here through analysis of covalent peptide grafting onto chitosan films for improved cell adhesion.

Free-solution capillary electrophoresis (CE) separates analytes, generally charged compounds in solution through the application of an electric field. ...

Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films

Organo-lead halide perovskites have recently attracted great interest for potential applications in thin-film photovoltaics and optoelectronics. Herein, we present a protocol for the fabrication of this material via the low-pressure vapor assisted solution process (LP-VASP) method, which yields ~19% power conversion efficiency in planar heterojunction perovskite solar cells. First, we report the synthesis of methylammonium iodide (CH3NH3I) and methylammonium bromide (CH3NH3Br) from methylamine and the corresponding halide acid (HI or HBr). Then, we describe the fabrication of pinhole-free, continuous methylammonium-lead halide perovskite (CH3NH3PbX3 with X = I, Br, Cl and their mixture) films with the LP-VASP. This process is based on two steps: i) spin-coating of a homogenous layer of lead halide precursor onto a substrate, and ii) conversion of this layer to CH3NH3PbI3-xBrx by exposing the substrate to vapors of a mixture of CH3NH3I and CH3NH3Br at reduced pressure and 120 &#176;C. Through slow diffusion of the methylammonium halide vapor into the lead halide precursor, we achieve slow and controlled growth of a continuous, pinhole-free perovskite film. The LP-VASP allows synthetic access to the full halide composition space in CH3NH3PbI3-xBrx with 0&#160;&#8804; x&#160;&#8804; 3. Depending on the composition of the vapor phase, the bandgap can be tuned between 1.6 eV&#160;&#8804; Eg&#160;&#8804; 2.3 eV. In addition, by varying the composition of the halide precursor and of the vapor phase, we can also obtain CH3NH3PbI3-xClx. Films obtained from the LP-VASP are reproducible, phase pure as confirmed by X-ray diffraction measurements, and show high photoluminescence quantum yield. The process does not require the use of a glovebox.

Here, we present a protocol for the synthesis of CH3NH3I and CH3NH3Br precursors and the subsequent formation of pinhole-free, continuous CH3NH3PbI3-xBrx thin films for the application in high efficiency solar cells and other optoelectronic devices.

Organo-lead halide perovskites have recently attracted great interest for potential applications in thin-film photovoltaics and optoelectronics. Herein, ...

Reactive Vapor Deposition of Conjugated Polymer Films on Arbitrary Substrates

We demonstrate a method of conformally coating conjugated polymers on arbitrary substrates using a custom-designed, low-pressure reaction chamber. Conductive polymers, poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-propylenedioxythiophene) (PProDOT), and a semiconducting polymer, poly(thieno[3,2-b]thiophene) (PTT), were deposited on unconventional highly-disordered and textured substrates with high surface areas, such as paper, towels and fabrics. This reported deposition chamber is an improvement of previous vapor reactors because our system can accommodate both volatile and nonvolatile monomers, such as 3,4-propylenedioxythiophene and thieno[3,2-b]thiophene. Utilization of both solid and liquid oxidants are also demonstrated. One limitation of this method is that it lacks sophisticated in situ thickness monitors. Polymer coatings made by the commonly used solution-based coating methods, such as spin-coating and surface grafting, are often not uniform or susceptible to mechanical degradation. This reported vapor phase deposition method overcomes those drawbacks and is a strong alternative to common solution-based coating methods. Notably, polymer films coated by the reported method are uniform and conformal on rough surfaces, even at a micrometer scale. This feature allows for future application of vapor deposited polymers in electronics devices on flexible and highly textured substrates.

This paper presents a protocol for reactive vapor deposition of poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), and poly(thieno[3,2-b]thiophene) films on glass slides and rough substrates, such as textiles and paper.

We demonstrate a method of conformally coating conjugated polymers on arbitrary substrates using a custom-designed, low-pressure reaction chamber. ...

Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 &#176;C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications.
In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods.

Here, we present a protocol for the synthesis of porous barium titanate (BaTiO3) thin film by a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles are used as an organic template.

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its ...

Inkjet Printing All Inorganic Halide Perovskite Inks for Photovoltaic Applications

A method for synthesizing photoactive inorganic&#160;perovskite quantum dot inks and an inkjet printer deposition method, using the synthesized inks, are demonstrated. The ink synthesis is based on a simple wet chemical reaction and the inkjet printing protocol is a facile step by step method. The inkjet printed thin films have been characterized by X-ray diffraction, optical absorption spectroscopy, photoluminescent spectroscopy, and electronic transport measurements. X-ray diffraction of the printed quantum dot films indicates a crystal structure consistent with an orthorhombic room temperature phase with (001) orientation. In conjunction with other characterization methods, the X-ray diffraction&#160;measurements show high quality films can be obtained through the inkjet printing method.

A protocol for synthesizing inorganic-lead-halide hybrid perovskite quantum dot inks for inkjet printing and the protocol for preparing and printing the quantum dot inks in an inkjet printer with post characterization techniques are presented.

A method for synthesizing photoactive inorganic&#160;perovskite quantum dot inks and an inkjet printer deposition method, using the synthesized inks, are ...