Perovskite Solar Cell - IEC Standard Testing

Prof. Henry Snaith from the University of Oxford shared that perovskite solar cells which are currently not commercialized yet will soon see the light of market. In his talk at ES01 (perovskite symposium session), he mentioned successful IEC standard testing on hybrid perovskite solar cells.

IEC standard testing includes testing the device at 85 deg C with 85% humidity, temperature cycling and full spectrum exposure. His results show more than 1000 hours of stability. 

His talk was focused on the stability of perovskite solar cells. He picked up each layer of the solar cell and commented on its stability through the experimental results from his lab. He started with n-type layer. He mentioned that Titanium dioxide is not stable under UV light. Tin Oxide (SnO2) is more stable. He mentioned that doping the p-type layer increases the current; however, fill factor and voltage were decreased. 

Hybrid perovskite stability is one of the biggest issues right now. He showed that a mixture of 2D and 3D perovskite is a stable form of perovskite. He mentioned that 2D perovskite can be observed at the grain boundaries and the bulk is 3D perovskite. 

His innovative approaches towards solving the issues related to perovskite solar cells are remarkable. 

Jennifer Leduc explaining the new concept of Poster Presentation at 2017 Fall MRS Meeting

Jennifer Ludec, a talented PhD student at the University of Cologne is one of the organizers of the international summit at the 2017 Fall MRS Meeting. They have introduced a new type of poster presentation. Each student got a chance to give an oral presentation at the symposium to advertise their poster. They were allowed one minute to market their work.

Watch Jennifer talking about their innovative poster session:

 

 

 

Follow me on Twitter: @rahim_munir1

I blog at "Succinct Monograph"

Follow me on Twitter: @rahim_munir1

I blog at "Succinct Monograph"

Isabel Gessner explaining the International Summit

Isabel Gressner is from the University of Cologne. She is one of the organizers of the International Summit at the 2017 Fall MRS Meeting. Her efforts are remarkable for arranging and organizing this fantastic summit.

Hear her explaining the new creative summit which was a big hit at the MRS meeting. 

 

 

 

Follow me on Twitter: @rahim_munir1

I blog at "Succinct Monograph"

 

NM07: Nanostructure-Based Optical Bioprobes—Advances, Trends and Challenges in Optical and Multimodular Bioimaging and Sensing

Shangfeng Wang, Fudan University

Ratiometric Imaging of Endogenous Hypochlorous Acid in the Second Near-Infrared Window beyond 1500 nm

Written by Xun Gong

This work reports a fluorescent nanoprobe for the ratiometric detection of reactive oxygen species (ROS) in the second near-infrared window (NIR-II: ∼1000–1700 nm) of lanthanide-based downconversion nanoparticle (NIR-IIb: ~1500-1700 nm). Imaging in NIR-II has many advantages in in vivo imaging including reduced attenuation, tissue scattering, and autofluorescence. The result is higher image quality. To further improve signal, ratiometric sensing is used. By having a built-in control, there is increased signal-to-noise ratio (SNR), decreased photobleaching, and effects of changing particle distributions.

Lanthanides have emission features in the NIR-II window. Downconversion luminescence excited under 808 nm can be effectively quenched by the Cy7.5 chromophores on the surface of nanoparticles through an absorption competition process and subsequently recovered upon the addition of ROS. The downconversion luminescence excited under 980 nm remains unchanged, making a 2 excitation wavelength ratiometric sensor. Optical phantom experiments show no significant signal change within 1-3 mm tissue depths. Finally, LPS injection in mouse studies show lymphnode increase in ROS with SNR of 19.7. This study provides a new design strategies of NIR-II fluorescent probes for precise and reliable measurement in biological systems.

BM06: 2D Nanomaterials in Health Care

Jacob Swett, Pawel Puczkarski, Xinya Bian and Jan Mol, University of Oxford

Towards Recognition Tunnelling Based DNA Sequencing with Graphene Nanogaps

Written by Xun Gong

Nanopore sequencing involves the study of the sequence of polymers via individual interrogation as the polymer traverses an open pore. This type of measurement will allow for long reads of single contiguous molecules, the order of base pairs in the case of DNA. Method of measurement usually electrical, measuring either across the membrane or directly across the pore. Traditionally the field can be divided into biological and solid-state methods, where the former uses biologically available channels as detection components. The advantage of solid state methods revolves around improved tunability and reduced fabrication costs.

This work reports on the fabrication progress and initial data from a solid-state single-molecule graphene nanogap-based biomolecular sensing architecture for DNA sequencing. The device is fabricated on a suspended SiN/Si architecture with metal electrodes fabricated through electron beam lithography and thermal evaporation. Apertures in the SiN, allowing for the translocation of DNA, are fabricated by focused ion beam milling and the graphene nanogaps are formed through a combination of electron beam lithography and feedback-controlled electroburning to create a narrow gap. The graphene is passivated through a dielectric coating with a co-aligned aperture, resulting in a single translocation pathway through the device. The architecture, which requires aligned <10 nm features in multiple layers, is characterized with SEM, AFM, and S/TEM. Due to the narrowness of the channels, this system can potentially achieve single base resolution.

BM02: Multiphase Fluids for Materials Science—Droplets, Bubbles and Emulsions

Maria Torres Arango, West Virginia University

Bio-Inspired Multiphase Processing, 3D Printing and Hierarchical Structuring of Metal-Oxide Cellular Frameworks

Written by Hortense Le Ferrand

Additive manufacturing enables the layer-by-layer building up of new architectured materials. Unfortunately, the challenge usually relies in the printability of “inks” and in their rheology. Targeting photocatalytic applications, Maria Torres Arango was able to print fully inorganic foams of titanium oxide with tunable pore size and interconnectivity.

To this end, she first developed an emulsion processing mixing titanium oxide nanoparticles, a titanium organic precursor with an oily phase containing surfactants and fatty acids. After frothing, this mixture forms a foam whose bubble sizes are related to the initial composition. The viscosity of this foam can be decreased from 50 Pa.s to less than 5 Pa.s under shear and recover this viscosity after release of shear. This shear-thinning capability makes the emulsion printable and bridges up to 5 mm long that can be extruded without collapsing. To remove the organics and strengthen the liquid emulsion into an inorganic porous material, 30 minutes at 150°C are sufficient to leave macropores resulting from the bubbles, micropores from the burning of the organics, and interconnects between the nanoparticles.

Surprisingly, the structure obtained by this method offers a smaller surface area thus lesser exposure to light, yet an increased photocatalytic activity: The irradiation can reach deeper into the material.

This study exemplifies not only how colloidal science is required to tune the properties of inks to satisfy printable conditions, but also how materials research can benefit from three-dimensional (3D) printing for concrete applications.

BM06: 2D Nanomaterials in Health Care

Valtencir Zucolotto, University of São Paulo

Immuno and DNA-Based Nanosensors Applied to the Rapid Detection of Infectious Diseases

Written by Xun Gong

Nanobiosensors have important applications as point-of-care diagnostic systems. Such systems usually contain a biological recognition element as well as signal transduction elements for rapid detection of analytes. One major group of such targets include Zika and Dengue viruses, for which prompt diagnosis will yield improved mortality and morbidity.

The Zucolotto group works with a wide array of particles as well as sensors for the detection of dopamine, pesticides, and food contaminants for example. This work proposes several types of recognition elements coupled to electronic circuits for read out:

• Leishmaniasis and Chagas disease: Antibody elements conjugated to lipidsomes are subjected to alternating electric fields between two parallel plate electrodes to measure capacitance. Multiple electrode types allow for PCA analysis of separation of analyte types.
• Dengue: The immunosensors comprised anti-NS1 antibodies immobilized on gold electrodes. Detection of the specific NS1 protein (a common Dengue biomarker) at concentrations as low as 0.25 ug mL^-1 was carried out using the field-effect transistor (FET) concept.
• Geno sensors for Dengue and Zika DNA: Electrodes containing DNA probes capable of hybridizing with specific target DNA sequences. After binding, a set of reporter DNA sequences is attached, complementary to another segment of the target DNA. Read out is performed via impedance measurement with a detection limit of 9.86 ± 0.89 nmol L^-1.

NM04: Atomically Thin, Layered and 2D Non-Carbon Materials and Systems

Aditya Mohite, Los Alamos National Laboratory

Emergence of Layered 2D Perovskites for High-Efficiency Optoelectronic Devices

Written by Natalie Briggs

Perovskite materials have seen increased study in recent years due to their potential for use in improved solar cell technologies. Aditya Mohite of Los Alamos National Laboratory has shown recently that two-dimensional hybrids of perovskite materials show potential for solar cells and even light-emitting diode technology. Mohite’s work shows that Ruddleson-Popper perovskites can be synthesized with varying thicknesses, where the materials exhibit the form of A’₂A_(n-1)B_nX_3(n+1), and materials with integer multiples of n can be realized. Interestingly, n=1 and n=2 systems show different characteristics from n=>3, where photoexcitation of compounds with n=1 or 2 indicate characteristics of radiative or nonradiative combination, and greater n values show exciton diffusion and dissociation via edge states. Devices created with these greater n value compounds show a 10% increase in efficiency compared to lower n values, and manipulation of these compounds allows for color tunability.

NM04: Atomically Thin, Layered and 2D Non-Carbon Materials and Systems

Andrey Krayev, AIST-NT Incorporated

Nanoscale Heterogeneities in Monolayer MoSe₂ and WSe₂ Revealed by Correlated SPM and TERS

Written by Natalie Briggs

The process of transferring few-layer, two-dimensional materials flakes is common in the study of intrinsic materials properties as well as the fabrication of heterostructures. While this process is widely acknowledged to be detrimental to materials quality, the exact effects or nature of materials damage is not well understood. Through the use of correlated scanning probe microscopy and tip-enhanced Raman spectroscopy (TERS), Andrey Krayev of AIST-NT Incorporated demonstrates that the correlation of these two techniques can clearly show defects in transferred flakes of monolayer MoSe₂ and WSe₂. For example, following layer transfer of MoSe₂ flakes via NaOH, Krayev observes evidence of MoO₃ incorporation in MoSe₂ flakes resulting in possible p-doping and effects, and variation in exciton distribution and ratios within the flakes. Additionally, transferred flakes of WSe₂ show formation of triangular holes following the transfer process, which are observed through correlation of friction and TERS mapping.

TC02: In Situ Studies of Materials Transformations

J. Tyler Mefford, Stanford University

Operando Electrochemical Scanning Transmission X-Ray Microscopy of Energy Conversion and Storage Electrode Materials

Written by Hortense Le Ferrand

Following the local oxidation states of oxides during electrochemistry brings more understanding about the reaction paths and subsequently on how to make and use more efficient batteries.

Using soft x-rays from a synchrotron source, with energy of 100-200 eV, Tyler Mefford and his colleagues have mapped the oxidation states across the 2-µm-wide surface of hexagonal crystals of cobalt hydroxide while electrochemistry is occurring. These crystals are 75 nm in thickness, thus opaque in transmission electron microscope (TEM) but thin enough to be studied by soft x-rays. These x-rays are particularly interesting as they provide fingerprint spectra of oxides states, otherwise not available using hard x-rays of higher energies.

Adapting to the x-ray set-up in situ holder designed to perform electrochemistry in TEM, the crystal is raster scanned with a pixel size of 25 nm. Each pixel contains the absorption energy spectra from which the oxidation states are extracted. Combining spatial with temporal resolution, the researchers have discovered that the two oxidation states of the cobalt hydroxide during water splitting are +2 to +2.65, then +2.65 to +3, instead of the transitions +2 to +3 then +3 to +4 as it was previously predicted. The very high spatial resolution revealed also that the edges of the crystals are the most active.

Using this technique to map battery materials during function, the researchers also study the effects of charging and discharging rates on the distribution of atoms, phase separation, or the propagation of defects. One major output of their research is that lithium batteries are more robust when charged at fast rates.