Symposium EL02: Fundamentals of Halide Semiconductors for Optoelectronics

Ruth Shinar, Iowa State University

Tunable Perovskite-Based Photodetectors in Optical Sensing

Written by Victor A. Rodriguez-Toro

Compact spectroscopic platforms for (bio)chemical sensing have been proposed in the past. Typically, it consists of a light source in the visible range that sends an optical pulse to photoexcite a phosphorescent dye, which is embedded in a thin film like polystyrene (PS). Once the visible light is turned off (end of the optical pulse), a signal of photoluminescence (at longer wavelength than the light source) is emitted from the dye and sensed by a photodetector (PD). Characteristics of the emitted signal (amplitude and decay time) depend on the interaction of the dye with the analyte (e.g., oxygen) to detect. As the analyte concentration increases, the amplitude of the photoluminescence signal is lower, and the decay time is shorter. Therefore, two measurement modes to determine the analyte concentration can be established by monitoring (1) the optical intensity or (2) decay time. The latter constrains the response time of the light source and the PD to be in the order of 1 ms. Furthermore, it is desirable that the PD to have a low external quantum efficiency (EQE) at the wavelengths of the light source, but a high EQE at the wavelengths of the emitted signal of photoluminescence. 

Shinar and co-workers present the assessment of various photodetection technologies. First, inorganic PDs based on inorganic materials such as amorphous silicon are evaluated making evident their long response time (~250 ms) and the need for external filters. Second, organic photodetectors (OPDs) based on the polymer P3HT and the acceptor PCBM were evaluated showing low EQE in the region of interest for detection.

Finally, perovskite photodetectors (PPDs) were evaluated showing a high EQE, fast response times, and the ability to have systems with broadband and narrowband photodetection sensitivity.

Symposium NM03: Topological and Quantum Phenomena in Intermetallic Compounds and Heterostructures

Sahal Kaushik, Stony Brook University

Late News: Tunable Chiral Symmetry Breaking in Symmetric Weyl Materials

Written by Jessalyn Hui Ying Low

Asymmetric Weyl materials have an inherently chiral crystal structure, but lack symmetry between left- and right-handed fermions. Due to these properties, they exhibit many unique phenomena such as the quantized circular photogalvanic effect, yet are much rarer as compared to symmetric Weyl materials. In this talk, Sahal Kaushik shows how by applying external perturbations, in particular external magnetic field, chiral symmetry in symmetric Weyl materials can be broken to become asymmetric.

With a focus on materials with the -43m (Td) point group, Kaushik explains that for chiral symmetry breaking, it is insufficient to break only reflection symmetries as this could induce false chirality. Rather, all combinations of reflection and time reversal should be broken. Therefore, for a measure of true chirality, the magnitude of the magnetic field must be different along all three directions, implying that chirality will be broken when the magnetic field is applied along low symmetry directions like [147] and not high symmetry directions like [001] and [111]. It was shown that when magnetic field was applied along low symmetry directions, left- and right-handed Weyl cones indeed showed different energies, velocities, and tilts. These symmetry breaking parameters were influenced by magnitude and direction of the magnetic field. Notably, as the direction of magnetic field increased in asymmetry, the discrepancy between left- and right-handed Weyl cones increased, highlighting how chirality symmetry breaking in Weyl materials can be tuned.

Congratulations to the 2021 Virtual MRS Spring Meeting Science as Art Winners!

First Place

2021 Spring Meeting Graduate Student Awards

The MRS Graduate Student Awards are intended to honor and encourage graduate students whose academic achievements and current materials research display a high level of excellence and distinction. In addition to the MRS Graduate Student Gold and Silver Awards, the Arthur Nowick Graduate Student Award, which honors the late Dr. Arthur Nowick and his lifelong commitment to teaching and mentoring students in materials science, will be presented to a GSA finalist who shows particular promise as a future teacher and mentor.



Chullhee Cho
Chullhee Cho

University of Illinois
at Urbana-Champaign

Ahyoung Kim
Ahyoung Kim
University of Illinois
at Urbana-Champaign

Joeson Wong
Joeson Wong
California Institute of Technology

Guomin Zhu
Guomin Zhu
University of Washington



Jingshan S. Du
Jingshan S. Du
Northwestern University

Nikita Dutta
Nikita Dutta (Nowick Prize)
Princeton University

Zhiwei Fang
Zhiwei Fang
The University of Texas at Austin

Hanson Wang
Hansen Wang
Stanford University


Hanson Wang
Jiayue Wang
Massachusetts Institute of Technology

Wanghuai Xu
Wanghuai Xu
City University of Hong Kong

MRS acknowledges the generous contribution for the Nowick Award to the MRS Foundation from Joan Nowick in memory of her husband Dr. Arthur Nowick.

Best Poster Winners–2021 Virtual MRS Spring Meeting

Hector Mandujano, The University of Texas at El Paso, (CT04.01.06)

Changho Hon, Seoul National University, (CT05.14.05)    

Yunseul Kim, Gwangju Institute of Science and Technology, (EL01.10.15)

Daniel Davies, University of Illinois at Urbana-Champaign, (EL01.14.10)  

Jingjing Shi, Georgia Institute of Technology, (EL04.13.07)             

Wonjin Choi, University of Michigan–Ann Arbor, (EL05.13.03)     

Komalika Rani, Université Paris-Saclay, (EL09.07.01)        

Sang Seob Lee, Yonsei University, (EN01.08.05) 

Alessia Fortunati, Politecnico di Torino, (EN02.01.06)      

Virgil Andrei, University of Cambridge, University of Cambridge, (EN02.06.03)     

Eman Alhajji, King Abdullah University of Science and Technology, (EN03.08.01) 

Teresa Cristina Rojas, Instituto de Ciencia de Materiales de Sevilla, (EN05.03.04)

Davide Moia, Max Planck Institute for Solid State Research, (EN06.10.08)              

Eric Chang, Duke University, (EN07.04.04)            

Albanie Hendrickson-Stives, The Pennsylvania State University, (NM05.04.05)    

Hyoung Taek Kim, Sungkyunkwan University, (NM09.10.02)        

Chunhong Dong, Georgia State University, (SM01.03.03)               

Sebastian Buchmann, KTH Royal Institute of Technology, (SM03.01.06)  

Jeong Eun Park, Inha University, (SM05.06.05)   

Jisoo Jeon, Inha University, Inha University, (SM07.08.09)             

Che-Hsuan Cheng, University of Michigan–Ann Arbor, (ST01.07.07)          

Hojang Kim, Korea Advanced Institute of Science and Technology, (ST01.11.06)  

Kooknoh Yoon, Seoul National University, (ST04.04.07)

Symposium X: Frontiers of Materials Research

Symposium X—Frontiers of Materials Research_yi-cuiYi Cui, Stanford University
Nanotechnology for Sustainability

Written by Sophia Chen

Yi Cui of Stanford University delivered a Symposium X lecture on Thursday. A materials scientist, Cui discussed nanotechnology applications in sustainability efforts, such as reduction of fossil fuel use and pandemic mitigation efforts. Just in his lab alone, they use nanotechnology to design better batteries, medical face masks, and clothing.

One thrust of his group’s research is “trying to reinvent the battery,” said Cui. Over the last 15 years, Cui’s group has tackled questions such as how to improve the energy density of batteries, how to extend their lifetime, how to reuse and recycle them, all while making sure the technology is safe. He sees his work as the next generation to lithium ion batteries, now in widespread use in portable electronics and electric vehicles, and whose pioneers received the Nobel Prize in 2019.

Cui has developed new batteries from higher energy density materials by optimizing the geometry of the materials inside the batteries. For example, his group has made lithium-ion batteries with anodes made of silicon nanowires instead of the conventional graphite. However, silicon poses design challenges, as it expands several times its original size as the battery discharges. This can cause the silicon nanowires to crack and break, so Cui’s group has developed a shell-like structure around the silicon to avoid the material fracturing. They have also made strides in developing lithium metal batteries—a “holy grail” for the field because of the metal’s theoretical energy density. But in reality, lithium metal is challenging to work with because the metal expands dramatically and breaks easily. To prevent this, Cui’s group has developed hollow nano-capsules for lithium metal to sit in.

His group has also developed new techniques for imaging the dynamics inside batteries. In 2016, they developed the technique of cryogenic electron microscopy, which freezes material and images the material at atomic-scale resolution.

Nanofibers can also make high quality air filters, such as those needed in medical face masks, said Cui. His group has achieved filters with 60% porosity made from fibers 10 µm in diameter, spaced apart by 15 µm. This produces a breathable mask using a tiny amount of material.

Clothing that cools or heats the wearer could also make a significant difference in energy consumption, said Cui. His group has designed a polyethylene textile that is more transparent to the infrared radiation produced by the human body compared to cotton. In tests, they found the material caused the wearer’s skin temperature to be nearly 3°C cooler than when the person was wearing cotton. He pointed out that changing heating or cooling by a single degree Celsius can, on average, alter energy usage by 10 percent.

It’s important to get these innovations in the hands of consumers quickly, said Cui. His company Amprius, founded in 2009, has commercialized the silicon nanowire anode battery technology. He has recently founded the startup Eenotech for commercializing the polyethylene material, whose spinoff company LifeLabs Design will sell a limited quantity of clothing made from the polyethylene material this summer.

At the end of 2020, Cui became the director of Stanford’s Precourt Institute for Energy. As director, Cui oversees a range of research spanning many fields. In addition to materials and other hard science research, the institute weaves together researchers studying sustainable finance, policy, human behavior, artificial intelligence, and more.

Symposium X—Frontiers of Materials Research features lectures aimed at a broad audience to provide meeting attendees with an overview of leading-edge topics.

Bringing Perovskite Photovolatics to Consumer Market

Have you ever wondered about the bridge between fundamental scientific research and the consumer market? Or whether or not that solar cell you have been studying for a while would actually make it to the end user? The MRS EN06.09 session presents you with the latest on how to "Bring Perovskites to the Real World for a Smart Future".

One interesting presentation, in this session was the talk by Professor Kylie Catchpole, of Australian National University, presenting on "High Efficiency Perovskite/Silicon Solar Cells and Solar Hydrogen Systems". In her talk, professor Catchpole highlighted the recent increase in installation of photovoltaics in general compared to other electricity production technologies. "Solar and wind energy nowadays are cheaper than coal" emphasized Professor Catchpole, as she explained that the energy production market is mainly driven by cost. Photovoltaics also have the potential to be a low-cost source of hydrogen and other solar fuels. Higher efficiency of solar panels guarantees to lessen the overall cost of solar systems by reducing the number of modules needed. 

The achievement of a highly efficient solar cell is limited by charge recombination processes. Professor Catchpole and her research team used various passivation techniques to enhance the efficiency of their perovskites solar cells. Passivation is the addition of an insulating layer in between the interfaces of the perovskites to prevent charge recombination, as explained by professor Catchpole. In one technique they used an ultrathin (about 5 nm) passivation layer, composed of a mixture of PMMA and PCBM, to achieve high voltage and fill factor. In another technique, a nanostructured electron transport layer was passivated by the PMMA and PCBM mixture. Professor Catchpole’s team was able to achieve an efficiency “above 21% and fill factor of 83% for a 1 cm2 single junction perovskite cell” using this technique. The third passivation technique presented by Professor Catchpole utilizing two-dimensional (2D) perovskites resulted in the remarkable efficiency of 27.7%, for a 4-terminal tandem perovskite/silicon configuration. At the end, Professor Catchpole demonstrated how they used perovskite/silicon tandems in combination with an appropriate catalyst to construct a water splitting system of 17% efficiency. For more on this talk please click here

A simple fundamental understanding of an observation or a phenomena is a goal on its own. It also feels good to see that your work is being used in everyday life. That was my view on Wednesday's virtual MRS Spring Meeting and Exhibit. I will miss writing to you and learning with you as this is my last blog, for now ;) Tot Ziens! 

Symposium SM11: Design and Analysis of Bioderived and Bioinspired Multifunctional Materials

Yeojin Jung, City College of New York

Programming Bombyx Mori Silk’s Water-Responsive Actuation Using Silica Nanoparticles

Written by Jessalyn Hui Ying Low

Spider silk is a water-responsive material found in nature and is known to be a great water-responsive actuator, but faces the issue of low availability. In this talk, Yeojin Jung shows how by engineering the Bombyx (B.) mori (silkworm) silk, water-responsiveness actuation can be enhanced, and even surpass that of natural muscles and spider silk. “Our findings could help apply natural silks as simple and scalable, but powerful water-responsive materials for practical applications,” says Jung.

Jung first explains that microstructure engineering can be used to increase the water-responsiveness of B. mori silk. By subjecting the silk to water vapor or methanol treatment, β-sheet crystallinity is increased. β-sheet nanostructures are capable of translating water energy into mechanical energy, thereby showing the potential for B. mori as actuators. Moreover, Jung shares that by adding stiff silica nanoparticles to mimic stiff β-sheet crystals, water-responsiveness could be significantly increased. Fourier-transform infrared spectroscopy (FTIR) studies additionally confirmed that the silica nanoparticles had minimal effect on the silk’s microstructure, with increase in water-responsiveness energy density due to the nanoparticles instead. With the addition of silica nanoparticles, water-responsiveness energy density of B. mori silk was found to be increased to ~ 700 kJ m-3, a value much higher than that of spider silk.

Symposium SM03: Advanced Neural Materials and Devices

Jihwan Lee, University of California, San Diego

High Density, Individually Addressable Silicon-Based Nanowire Arrays Record Native Intracellular Activity from Primary Rodent Neurons without Electroporation

Written by Arun Kumar

Jihwan Lee from the University of California, San Diego says that many questions regarding neurons can be answered by looking at intracellular recordings from neurons and the neuronal networks. High spatiotemporal resolution and minimal invasiveness are essential requirements for understanding altered neuronal functions during diseased conditions and their response to drugs. The prevalently used method for probing intracellular potentials, the patch-clamp technique offers high signal fidelity but is limited in its throughput, scalability, and invasiveness. Planar microelectrode arrays can provide high throughput and a highly scalable process but are limited in their low signal fidelity. On the other hand, vertical nanowire arrays present an innovative nanoscale device providing high fidelity, throughput, and scalability.

Unlike prior nanoelectrode processes, Jihwan Lee states that their process does not involve any optoporation/electroporative technique to transiently permeate the cells and measure the intracellular potentials. This potentially helps reduce the damage caused to the cells. He states that their arrays can measure the native recording of graded potentials without attenuation of the signal amplitude during the experimentation. Increasing spike activity was recorded by the sensors during primary rat neuronal cell development and maturation. Lee also shows how the recorded spike activity and frequency of spikes vary during the addition of drugs. Apart from neurons, effective action potential measurements were also made from cultured cardiovascular progenitor cells. The non-electroporative, non-optoporative, sharp-nanowire array for intracellular sensing applications could be a cost-effective screening method for studying neuronal dynamics and neurological disease pathology.

Symposium SM08: Next-Generation Materials and Technologies for 3D Printing and Bioprinting

Jingjun Wu, Zhejiang University

Soft Hydrogels as Anti-Adhesion Interfaces for Rapid Digital Light 3D Printing

Written by Jessalyn Hui Ying Low

Bottom-up digital light processing (DLP) is a vat polymerization technique commonly used for three-dimensional (3D) printing applications; however, printing speed is limited by the adhesion between the cured part and curing window, limiting applications in large-scale manufacturing. In this talk, Jingjun Wu reports the use of soft and deformable hydrogels to achieve solid-solid, but soft interface between the two parts, which will allow for reduced separation force and high printing speeds.

Wu explains that this is achieved by adding the hydrogel interface between the liquid resin and bottom glass window. By decreasing the modulus and increasing the thickness of the hydrogel, separation force can be decreased. Using this hydrogel interface, lower separation forces were achieved as compared to using fluorinated ethylene propylene (FEP) interface, which is the technique commercially used. This lower separation force was attributed to the ability for localized deformation induced separation in the hydrogel interface, unlike in FEP. Furthermore, it was found that using a printer equipped with such hydrogel interface allowed for a high printing speed as fast as 400 mm/h. Wu shares that these hydrogels exhibited mechanical stability during printing as well as good compatibility with the resin. Importantly, printing resolution is not compromised, therefore making 3D printers with these soft hydrogels favorable for achieving rapid 3D printing.