Developing Self-Complementary Macrocycles with Ingenious Molecules

Virus capsids can be formed through the self-complementary assembly of a single class of protein molecules. However, mimicking nature by making higher-ordered structures from artificial molecules has proven difficult to achieve. A new assembly method developed by Tokyo Tech researchers can produce stable and controllable supramolecular structures, from hexamers to cuboctahedrons that include 6 and 108 monomer units, respectively, opening doors to metal-free supramolecular assemblies.

Some biological molecules with efficient noncovalent bonding sites can use their bonding properties to create well-defined assemblies from a single class of molecules–i.e., they assemble with each other. These molecules, which are frequently seen in nature, are referred to as "self-complementary assemblies." For instance, the p24 protein hexamer, which is part of the capsid of the HIV (human immunodeficiency virus), is composed of six protein subunits which complementarily self -assemble using many hydrogen bonds. This phenomenon provides well-designed molecules can form higher-ordered assemblies without the metal ions which are commonly used as "joints" between monomer molecules. Indeed, many self-complementary assemblies have been reported on the basis of intrinsic hydrogen bonds, π-interactions, and coordination bonds.

Sustainable kerosene: accelerate production on an industrial scale

In the international project CARE-O-SENE, researchers are developing tailor-made Fischer-Tropsch catalysts for the production of sustainable kerosene.
Photo credit: Tiziana Carambia

The Federal Ministry of Education and Research (BMBF) is funding the international research project CARE-O-SENE (Catalyst Research for Sustainable Kerosene) with 30 million euros. It is intended to improve the production of sustainable kerosene on an industrial scale. For this purpose, the network partners, including the Karlsruhe Institute of Technology (KIT), are developing tailor-made catalysts to further develop the Fischer-Tropsch synthesis (FTS) established in fuel production for the use of renewable energy sources.

With a share of more than 80 percent, fossil fuels are still by far the most important raw material for fuels, heating and the chemical industry (source: International Energy Agency, IEA). Sustainable fuels are based on green hydrogen and carbon dioxide - and should make a significant contribution to decarbonizing sectors such as aviation, in which fossil fuels are particularly difficult to replace. In the CARE-O-SENE project, seven South African and German project partners are therefore researching next-generation Fischer-Tropsch catalysts.

Scientists Improve Inexpensive Perovskite Photocells

Simulated atomic structure of perovskite after calcium doping.
Illustration: Danil Bukhvalov

UrFU scientists have found a way to protect perovskite solar cells based on lead-methylammonium iodide (a promising alternative to traditional silicon photovoltaic cells) from degradation by water, such as rain. They found that partial replacement of lead with other alkaline earth metals protects them from such degradation, and also increases the parts of the visible spectrum of radiation involved in the process of generating electrons. An article on the results of the study was published in the Journal of Solid State Chemistry. The research was financially supported by the Ministry of Education and Science of Russia under the Priority 2030 development program of Ural Federal University.

Perovskite solar cells based on lead-methylammonium iodide are superior to silicon cells in performance and ease of synthesis. They are also capable of effectively generating electricity in cloudy or foggy conditions, so they are ideal for use in Russia or countries with similar climates. However, a complete switch to perovskite solar panels is not possible due to a number of reasons causing instability of such photovoltaic cells.

One of the causes of instability is that the compound is unstable to contact with water or other organic solvents. If it rains on the photocell, the compound begins to degrade rapidly, destroying its structure. Scientists determined that replacing lead with metals such as calcium, barium, or strontium would protect the compound from rapid degradation.

Graphene Boosts Flexible and Wearable Electronics

At 200 times stronger than steel, graphene has been hailed as a super material of the future since its discovery in 2004. The ultrathin carbon material is an incredibly strong electrical and thermal conductor, making it a perfect ingredient to enhance semiconductor chips found in many electrical devices.

But while graphene-based research has been fast-tracked, the nanomaterial has hit roadblocks: in particular, manufacturers have not been able to create large, industrially relevant amounts of the material. New research from the laboratory of Nai-Chang Yeh, the Thomas W. Hogan Professor of Physics, is reinvigorating the graphene craze.

In two new studies, the researchers demonstrate that graphene can greatly improve electrical circuits required for wearable and flexible electronics such as smart health patches, bendable smartphones, helmets, large folding display screens, and more.

In one study, published in ACS Applied Materials & Interfaces, the researchers grew graphene directly onto thin two-dimensional copper lines commonly used in electronics. The results showed that the graphene not only improved the lines' conducting properties but also protected the copper-based structures from usual wear and tear. For instance, they showed that graphene-coated copper structures could be folded 200,000 times without damage, as compared to the original copper structures, which started cracking after 20,000 folds. The results demonstrate that graphene can help create flexible electronics with longer lifetimes.

Ink flows to meet surging demand for national security research

Student interns are introduced to Sandia National Laboratories’ superfuge by test operations engineer Orlando Abeyta during a tour. Several new agreements signed this year are expected to increase the numbers of students and faculty partnering with Sandia to support its growing national security workload.
Photo credit: Craig Fritz

The nation’s largest national laboratory is embarking on a major expansion of its network of academic partners to meet the surging demand for national security science and engineering.

This year, Sandia National Laboratories inked memoranda of understanding with Texas A&M University; the University of California, Berkeley; North Carolina State University and the University of Texas at El Paso. It is finalizing agreements with Arizona State University and the University of Washington. When those are signed, Sandia will have formal ties with 27 universities, including 13 minority serving institutions.

Work at Sandia, which is performed almost entirely for federal agencies, has been rising steadily. From fiscal year 2015 to fiscal year 2021, the Labs’ budget increased more than 50%, from $2.9 billion to $4.5 billion. Over the same period, the Labs increased its workforce by more than 25%, from 11,700 to 15,000.

But Sandia won’t meet its obligations just by hiring staff.

“Partnering with universities keeps Sandia science at the state of the art and enables us to do more research for our national security mission than we can on our sites alone,” said Diane Peebles, Sandia’s senior manager of academic programs.

Digging deep

The unassuming Pacific mole crab, Emerita analoga, is about to make some waves. UC Berkeley researchers have debuted a unique robot inspired by this burrowing crustacean that may someday help evaluate the soil of agricultural sites, collect marine data and study soil and rock conditions at construction sites.

In a study published today in Frontiers in Robotics & AI, Hannah Stuart, assistant professor of mechanical engineering, and her team demonstrated one of the first legged robots that can self-burrow vertically. This digging robot, called EMBUR (EMerita BUrrowing Robot), uses a novel leg design to achieve downward motion that emulates the way Pacific mole crabs bury themselves in beach sand.

Mole crabs make burrowing look easy, but, according to Laura Treers, the study’s lead author and a Ph.D. student in mechanical engineering in Stuart’s Embodied Dexterity research group, it is difficult to move downward through granular media, like sand and soil. The deeper an animal digs, the harder the grains push back, impeding excavation.

To overcome this challenge and create a vertical-legged burrower, the researchers designed the legs of the robot to have an anisotropic force response, which means that they experience much greater force in one direction than another. Like a swimmer, the soft fabric legs of this robot expand for large forces during the power stroke, but fold and retract during the return stroke.

Claims AI can boost workplace diversity are ‘spurious and dangerous’, researchers argue

Co-author Dr Eleanor Drage testing the 'personality machine' built by Cambridge undergraduates.
  Credit: Eleanor Drage

Recent years have seen the emergence of AI tools marketed as an answer to lack of diversity in the workforce, from use of chatbots and CV scrapers to line up prospective candidates, through to analysis software for video interviews.

Those behind the technology claim it cancels out human biases against gender and ethnicity during recruitment, instead using algorithms that read vocabulary, speech patterns and even facial micro-expressions to assess huge pools of job applicants for the right personality type and “culture fit”.

However, in a new report published in Philosophy and Technology, researchers from Cambridge’s Centre for Gender Studies argue these claims make some uses of AI in hiring little better than an “automated pseudoscience” reminiscent of physiognomy or phrenology: the discredited beliefs that personality can be deduced from facial features or skull shape.

They say it is a dangerous example of “techno solutionism”: turning to technology to provide quick fixes for deep-rooted discrimination issues that require investment and changes to company culture.

Miniature Permanent Magnets Can Be Printed on a 3D Printer

3D-printing technology reduces production time of magnets by 30%.
Photo credit: Oksana Meleshchuk

Scientists from the Ural Federal University and the Ural Branch of the Russian Academy of Sciences are determining the optimal conditions for 3D printing of permanent magnets from hard magnetic compounds based on rare-earth metals. This will make it possible to start small-scale production of magnets, give them any shape during manufacturing, and create complex configurations of magnets. Such magnets are suitable for miniature electric motors and electric generators, on which pacemakers work. In addition, the technology minimizes production waste and has a shorter production cycle. A description of the method and experimental results are presented in the Journal of Magnetism and Magnetic Materials.

Creating complex and small magnets is not an easy scientific and technical task, but they are in demand in various specialized applications, primarily medical ones. One of the most promising ways to create complex-shaped parts from magnetically hard materials is 3D printing. Ural scientists managed to determine the optimal parameters for 3D printing of permanent magnets using the selective laser sintering method. This is an additive manufacturing method in which magnetic material in the form of powder is sintered layer by layer into a three-dimensional product of a given shape based on a previously created 3D model. This technology makes it possible to change the internal properties of the magnet at almost all stages of production. For example, to change the chemical composition of the compound, the degree of spatial orientation of crystallites and crystallographic texture, and to influence the coercivity (resistance to demagnetization).

On-site reactors could affordably turn CO2 into valuable chemicals

 Left: a schematic showing the key components of the reactor and working mechanism.
Right: a picture of the CO2 stack, which is a demonstration of the commercial reactors.
Credit: Dr. Zhongwei Chen, a chemical engineering professor at the University of Waterloo

New technology developed at the University of Waterloo could make a significant difference in the fight against climate change by affordably converting harmful carbon dioxide (CO2) into fuels and other valuable chemicals on an industrial scale.

Outlined in a study published today in the journal Nature Energy, the system yields 10 times more carbon monoxide (CO) – which can be used to make ethanol, methane and other desirable substances – than existing, small-scale technologies now limited to testing in laboratories.

Its individual cells can also be stacked to form reactors of any size, making the technology a customizable, economically viable solution that could be installed right on site, for example, at factories with CO2 emissions.

“This is a critical bridge to connect CO2 lab technology to industrial applications,” said Dr. Zhongwei Chen, a chemical engineering professor at Waterloo. “Without it, it is very difficult for materials-based technologies to be used commercially because they are just too expensive.”

Seaweed-based battery powers confidence in sustainable energy storage

Bristol-led team uses nanomaterials made from seaweed to create a strong battery separator, paving the way for greener and more efficient energy storage.

Sodium-metal batteries (SMBs) are one of the most promising high-energy and low-cost energy storage systems for the next-generation of large-scale applications. However, one of the major impediments to the development of SMBs is uncontrolled dendrite growth, which penetrates the battery’s separator and results in short-circuiting.

Building on previous work at the University of Bristol and in collaboration with Imperial College and University College London, the team has succeeded in making a separator from cellulose nanomaterials derived from brown seaweed.

The research, published in Advanced Materials, describes how fibers containing these seaweed-derived nanomaterials not only stop crystals from the sodium electrodes penetrating the separator, they also improve the performance of the batteries.

Driving high? Chemists make strides toward a marijuana breath analyzer

The researchers’ THC-powered fuel cell sensor, with its H-shaped glass chamber.
Credit: Evan Darzi 

A UCLA chemist and colleagues are now a step closer to their goal of developing a handheld tool similar to an alcohol Breathalyzer that can detect THC on a person’s breath after they’ve smoked marijuana.

In a paper published in the journal Organic Letters, UCLA organic chemistry professor Neil Garg and researchers from the UCLA startup ElectraTect Inc. describe the process by which THC introduced, in a solution, into their laboratory-built device can be oxidized, creating an electric current whose strength indicates how much of the psychoactive compound is present.

With the recent legalization or decriminalization of marijuana in many states, including California, the availability of a Breathalyzer-like tool could help make roadways safer, the researchers said. Studies have shown that consumption of marijuana impairs certain driving skills and is associated with a significantly elevated risk of accidents.

In 2020, Garg and UCLA postdoctoral researcher Evan Darzi discovered that removing a hydrogen molecule from the larger THC molecule caused it to change colors in a detectable way. The process, known as oxidation, is similar to that used in alcohol breath analyzers, which convert ethanol into an organic chemical compound through the loss of hydrogen. In most modern alcohol breath analyzer devices, this oxidation leads to an electric current that shows the presence and concentration of ethanol in the breath.

Since their 2020 finding, the researchers have been working with their patent-pending oxidation technology to develop a THC breath analyzer that works similarly. ElectraTect has exclusively licensed the patent rights from UCLA.

Solar Harvesting System has Potential to Generate Solar Power 24/7

Bo Zhao, Kalsi Assistant Professor of mechanical engineering, and his doctoral student, Sina Jafari Ghalekohneh, have created new architecture that improves the efficiency of solar energy harvesting to the thermodynamic limit.
Source: University of Houston

The great inventor Thomas Edison once said, “So long as the sun shines, man will be able to develop power in abundance.”

He wasn’t the first great mind to marvel at the notion of harnessing the power of the sun; for centuries inventors have been pondering and perfecting the way to harvest solar energy.

They’ve done an amazing job with photovoltaic cells which convert sunlight directly into energy. And still, with all the research, history and science behind it, there are limits to how much solar power can be harvested and used – as its generation is restricted only to the daytime.

A University of Houston professor is continuing the historic quest, reporting on a new type of solar energy harvesting system that breaks the efficiency record of all existing technologies. And no less important, it clears the way to use solar power 24/7.

"With our architecture, the solar energy harvesting efficiency can be improved to the thermodynamic limit,” reports Bo Zhao, Kalsi Assistant Professor of mechanical engineering and his doctoral student Sina Jafari Ghalekohneh in the journal Physical Review Applied. The thermodynamic limit is the absolute maximum theoretically possible conversion efficiency of sunlight into electricity.

Finding more efficient ways to harness solar energy is critical to transitioning to a carbon-free electric grid. According to a recent study by the U.S. Department of Energy Solar Energy Technologies Office and the National Renewable Energy Laboratory, solar could account for as much as 40% of the nation’s electricity supply by 2035 and 45% by 2050, pending aggressive cost reductions, supportive policies and large-scale electrification.

Technology for Conditioning Radioactive Waste Developed in Ural Region

The containers have a metal insert with a sorbent.
Photo credit: EKSORB press-service

Ural specialists have developed and tested a technology for conditioning (conversion from liquid to solid state) of liquid radioactive waste. The traditional scheme involves mixing sorbent enriched with radioactive isotopes of cesium-134 and 137 and cobalt-60 during the purification of liquid radioactive waste with cement mortar and placing it in special concrete protective containers. However, this requires a large number of containers, which increases the cost of processing and the volume of storage facilities to place the containers. Composite inorganic sorbents have been gaining popularity lately because they concentrate radionuclides very well from a large volume of liquid with a small volume of the sorbents themselves.

Scientists have developed a technology that makes it possible to condition liquid radioactive waste and then safely store the resulting solid waste. The technology is being developed by the EKSORB Scientific Production Enterprise (Ekaterinburg) with the support of the Foundation for Assistance to Innovations and in cooperation with the Ural Federal University.

The specialists tested the technology on a pilot plant. It was used to clean more than three cubic meters of liquid radioactive waste of BN-350 Reactor. As a result, the activity of cesium-137 decreased from 78 million Bq/L to 20 Bq/L, cobalt-60 - from 10 thousand Bq/L to less than 400 Bq/L. The clean concrete product was obtained from the cleaned solutions. After cleaning, the resulting solid waste can be stored safely, the developers assure.

Specialized smart soft contact lenses can address global issues of glaucoma diagnosis and management

New smart soft contact lens technology developed by a multidisciplinary team of engineers and health care researchers at Purdue University and Indiana University School of Optometry looks to gather important intraocular pressure measurements for 24-hour cycles as a way to detect glaucoma.
Credit: Purdue University photo/Rebecca McElhoe

The vision of Purdue University biomedical engineer Chi Hwan Lee to develop specialized smart soft contact lenses that can accurately measure intraocular pressure (IOP) in a person’s eye could be the latest answer to stopping glaucoma-related blindness.

Lee, the Leslie A. Geddes Associate Professor of Biomedical Engineering in Purdue’s Weldon School of Biomedical Engineering, led a research team that developed new ocular technology to continuously monitor patients’ IOP readings more comfortably and accurately.

The technology serves as another option for eye specialists to identify glaucoma, which, according to the Glaucoma Research Foundation, can steal a person’s vision without early warning signs or pain and affects more than 80 million people worldwide.

The only known modifiable risk factor is lowering a person’s IOP, which is difficult to monitor for long periods of time, particularly during sleep.

While exams can be performed in a specialist’s office and at-home monitoring systems are available, these all have their limitations. For instance, in-office measures are time-consuming, and current at-home technology is difficult to use, is uncomfortable and doesn’t gather sufficient data at the right time periods or over long enough time periods for specialists to appropriately use the information to make optimized treatment decisions.

Exploring Europa Possible with Silicon-Germanium Transistor Technology

Europa Image
Credit: NASA/JPL-Caltech/SETI Institute

Europa is more than just one of Jupiter’s many moons – it’s also one of most promising places in the solar system to look for extraterrestrial life. Under 10 kilometers of ice is a liquid water ocean that could sustain life. But with surface temperatures at -180 Celsius and with extreme levels of radiation, it’s also one of the most inhospitable places in the solar system. Exploring Europa could be possible in the coming years thanks to new applications for silicon-germanium transistor technology research at Georgia Tech.

Regents’ Professor John D. Cressler in the School of Electrical and Computer Engineering (ECE) and his students have been working with silicon-germanium heterojunction bipolar transistors (SiGe HBTs) for decades and have found them to have unique advantages in extreme environments like Europa.

“Due to the way that they're made, these devices actually survive those extreme conditions without any changes made to the underlying technology itself,” said Cressler, who is the project investigator. “You can build it for what you want it to do on Earth, and you then can use it in space.”

The researchers are in year one of a three-year grant in the NASA Concepts for Ocean Worlds Life Detection Technology (COLDTech) program to design the electronics infrastructure for upcoming Europa surface missions. NASA plans to launch the Europa Clipper in 2024, an orbiting spacecraft that will map the oceans of Europa, and then eventually send a landing vehicle, Europa Lander, to drill through the ice and explore its ocean. But it all starts with electronics that can function in Europa’s extreme environment.

Cressler and his students, together with researchers from NASA Jet Propulsion Lab (JPL) and the University of Tennessee (UT), demonstrated the capabilities of SiGe HBTs for this hostile environment in a paper presented at the IEEE Nuclear and Space Radiation Effects Conference in July.

Queen Mary chemical engineers have developed technologies to slash energy consumption in industry

Photo Credit: Quinten de Graaf

In two papers published in the journals Nature and Science, Queen Mary's Professor Livingston and Dr Zhiwei Jiang present their work on nanomembranes – exquisitely thin membranes that can provide an energy efficient alternative to current industry practices.

They demonstrate their technology can be used to refine crude oil and cannabidiol (CBD) oil – two industry giants. Around 80 million barrels of crude oil are processed every day to create fuel and plastic, in a process which consumes massive amounts of energy. The cannabidiol oil industry is fast growing - the Global Cannabidiol (CBD) Market is estimated to reach USD 47.22 Billion by 2028, up from USD 4.9 Billion in 2021.

Andrew Livingston, Professor of Chemical Engineering at Queen Mary, said: 'A vast amount of energy is consumed in industry separating molecules. The aim of our research is to provide low energy alternatives to these processes. Due to the innovations in the chemistry we used to make these membranes, we can achieve molecular architectures that achieve exquisite separations, and provide less resource intensive techniques for the separation of molecules.'

Dr Zhiwei Jiang, Research Associate at Queen Mary, said: 'Thinner is better - the liquid passes through the membranes much more quickly, rapidly speeding up the process, and therefore reducing the plant footprint while processing the same quantity of liquids.’

Container for Hazardous Radioactive Waste Storage Model Created

According to Oleg Tashlykov, the container protects from radiation in all directions.
Photo Credit: Anastasia Farafontova

Ural Federal University scientists designed a container to store solidified liquid radioactive waste containing "long-lived" cesium-137 and cobalt-60, the most potentially dangerous of all radioactive waste. Due to their innovative design and filling, the simulated containers are capable of reducing radiation from radioactive waste to safe levels. One such container could replace five or six of the standard type. An article about the scientific work was published in the journal Progress in Nuclear Energy.

The modeled container consists of three main layers: a stainless steel inner capsule, halloysite clay filler, and an outer cementation concrete layer. The stainless steel capsule holds more than 450,000 cm3 of radioactive waste. Radionuclides are concentrated in a special sorbent, which is used in ion-selective purification and is placed inside the capsule. Stainless steel was chosen because, unlike carbon steel, it is more resistant to corrosion and does not require shielding.

"As a rule, such containers consist of two layers: outer cementation concrete and an inner metallic hosting capsule with a radioactive sorbent (or a sorbent in a cement matrix is placed inside the container). The main disadvantage of such a container arrangement is that their shielding, i.e. protective, capacity is limited. We suggest a three-layer container - with an additional layer between the inner metal capsule and the outer shell. The material that fills this space must be inexpensive and still effectively reduce the gamma radiation emitted by the radioisotopes inside the radioactive waste container. In this case, we investigated the protective properties of the intermediate layer consisting of halloysite - a fine-dispersed nanoscale white clay with a chemical composition rich in aluminum and silicon," says Oleg Tashlykov, Associate Professor at the Department of Nuclear Power Plants and Renewable Energy Sources at UrFU, Head of Research and one of the authors of the article.

Power supply: Understand unstable networks

A stable power grid is essential for a reliable and sustainable energy system.
Photo credit: Markus Breig / KIT

A sustainable energy supply requires the expansion of the power grids. However, new lines can also make networks not more stable as expected, but more unstable. The phenomenon is called Braess paradox. This has now been simulated for the first time in detail for power grids, demonstrated on a larger scale and developed a forecasting instrument by an international team in which researchers from the Karlsruhe Institute of Technology (KIT) are also involved. It is intended to support network operators in making decisions. The researchers report in the journal Nature Communications. 

The sustainable transformation of the energy system requires an expansion of the networks in order to integrate renewable sources and to transport electricity over long distances. This expansion requires large investments and aims to make the networks more stable. By upgrading existing lines or adding new lines, it can also happen that the network does not become more stable, but more unstable and there are power outages. “We then speak of the Braess paradox. This means that an additional option instead of improvement leads to a deterioration in the overall situation,” says Dr. Benjamin Schäfer, head of the research group Data-driven Analysis of Complex Systems (DRACOS) at the Institute for Automation and Applied Computer Science at KIT.

The phenomenon is named after the German mathematician Dietrich Braess, who first discussed it for road networks: under certain conditions, the construction of a new road can extend the travel time for all road users. This effect was observed in traffic systems and discussed for biological systems, but has so far only been theoretically forecast for power grids and presented on a very small scale.

New light for shaping electron beams

Recent experiments at the University of Vienna show that light (red) can be used to arbitrarily shape electron beams (yellow), opening new possibilities in electron microscopy and metrology.
Credit: stefaneder.at, University of Vienna

A new technique that combines electron microscopy and laser technology enables programable, arbitrary shaping of electron beams. It can potentially be used for optimizing electron optics and for adaptive electron microscopy, maximizing sensitivity while minimizing beam-induced damage. This fundamental and disruptive technology was now demonstrated by researchers at the University of Vienna, and the University of Siegen. The results are published in PRX.

When light passes through turbulent or dense material, e.g. the Earth’s atmosphere or a millimeter-thick tissue, standard imaging technologies experience significant limitations in the imaging quality. Scientists therefore place deformable mirrors in the optical path of the telescope or microscope, which cancel out the undesired effects. This so-called adaptive optics has led to many breakthroughs in astronomy and deep-tissue imaging.

However, this level of control has not yet been achieved in electron optics even though many applications in materials science and structural biology demand it. In electron optics, scientists use beams of electrons instead of light to image structures with atomic resolution. Usually, static electromagnetic fields are used to steer and focus the electron beams.

Novel Carrier Doping in p-type Semiconductors Enhances Photovoltaic Device Performance by Increasing Hole Concentration

The carrier concentration and conductivity in p-type monovalent copper semiconductors can be significantly enhanced by adding alkali metal impurities, as shown recently by Tokyo Tech researchers. Doping with isovalent and larger-sized alkali metal ions effectively increased the free charge carrier concentration and the mechanism was unraveled by their theoretical calculations. Their carrier doping technology enables high carrier concentration and high mobility p-type thin films to be prepared from the solution process, with photovoltaic device applications.

Perovskite solar cells have been the subject of much research as the next generation of photovoltaic devices. However, many challenges remain to be overcome for the practical application. One of them concerns the hole transport layer (p-type semiconductor) in photovoltaic cells that carries holes generated by light to the electrode. In conventional p-type organic transport semiconductors, hole dopants are chemically reactive and degrade the photovoltaic device. Inorganic p-type semiconductors, which are chemically stable, are promising alternatives, but fabrication of conventional inorganic p-type semiconductors requires high temperature treatment. In this regard, the p-type inorganic semiconductors that can be fabricated at low temperatures and have excellent hole transport ability have been desired.

Inorganic p-type copper iodide (CuI) semiconductor is a leading candidate for such hole transport materials in photovoltaic device applications. In this material, native defects give rise to charge imbalance and free charge carriers. However, the overall number of defects is generally too low for satisfactory device performance.