Take a survey on risk management of nanotechnology

The EU FP7 Sustainable Nanotechnologies (SUN) project is based on the idea that the current knowledge on environmental and health risks of nanomaterials – while limited – can nevertheless guide nanomanufacturing to avoid liabilities if an integrated approach addressing the complete product lifecycle is applied. SUN project logo
SUN aims to evaluate the risks along the supply chains of engineered nanomaterials and incorporate the results into tools and guidelines for sustainable nanomanufacturing.

A key objective of SUN is to build the SUN Decision Support System (SUNDS) to facilitate safe and sustainable nanomanufacturing and risk management. It will integrate tools for ecological and human health risk assessment, lifecycle assessment, economic assessment and social impact assessment within a sustainability assessment framework.

The project team is currently developing the Technological Alternatives and Risk Management Measures (TARMM) inventory and are looking for companies to fill in a short survey of questions.

The goal of this questionnaire is to collect information to support the development of TARMM inventory by surveying companies that are involved in nanotechnology-related activities. Personnel who are familiar with the risk management practices in your company may be best suited to answer these questions. It consists of 12 questions related to risk management of nano-enabled products.

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Stable perovskite solar cells developed through structural simplification

Perovskite solar cells are promising low-cost and highly-efficient next-generation solar cells. The ad hoc Team on Perovskite PV Cells (Kenjiro Miyano, Team Leader) at the Global Research Center for Environment and Energy based on Nanomaterials Science (GREEN) (Kohei Uosaki, Director-General), NIMS (Sukekatsu Ushioda, President), successfully developed perovskite solar cells with good reproducibility and stability as well as exhibiting ideal semiconducting properties (, "Simple characterization of electronic processes in perovskite photovoltaic cells"). Schematic diagram of a perovskite solar cell and its cross section viewed with a scanning electron microscope Schematic diagram of a perovskite solar cell and its cross section viewed with a scanning electron microscope. Light passes through a transparent electrode and is absorbed by the perovskite layer, generating positive (holes) and negative (electrons) charges by means of photoexcitation. Electrons in the perovskite layer move to the PCBM electron transport layer. Holes travel through the hole transport layer and are extracted from the transparent electrode, generating electric power. Lead-halide-based perovskite (hereinafter simply referred to as perovskite) has been used as a solar cell material since six years ago. Perovskite solar cells are promising low-cost and highly-efficient next-generation solar cells because they can be produced through low-temperature processes such as spin coating, and generate a large amount of electricity due to their high optical absorption together with the high open-circuit voltage. As such, the research on perovskite solar cells is making rapid progress. In order to identify the semiconducting properties of perovskites and formulate guidelines for the development of highly efficient solar cell materials, NIMS launched an ad hoc Team on Perovskite PV Cells last October led by the deputy director-general of GREEN. While the conventional perovskite solar cells have demonstrated high conversion efficiency, they were not sufficiently stable plagued by their low reproducibility and the hysteresis in the current-voltage curves depending on the direction of the voltage sweeps. For this reason, the semiconducting properties of perovskites had not been identified. We successfully created reproducible and stable perovskite solar cells as follows;
  • We created perovskite solar cells with a simplified structure while strictly eliminating moisture and oxygen by employing the fabrication technique we have developed for the organic solar cells in the past.
  • We found that our perovskite solar cells are stable and we observed no hysteresis in the current-voltage curve. Furthermore, we found that the perovskite solar cell material serves as an excellent semiconductor with ideal diode properties.
We proposed an equivalent circuit model that explains the semiconducting properties of perovskites based on analysis of the internal resistance of perovskite solar cells. This model indicated the existence of a charge transport process derived from an impurity level between the conduction and valence bands in the perovskite layer. Due to this transport process, the efficiency of perovskite solar cells may be suppressed to some extent. In future studies, we will investigate into the cause of the impurity level and its influence on solar cells. In addition, we intend to remove the impurity level and improve the efficiency of the solar cells, thereby contributing to energy and environmental conservation. This study was conducted at GREEN as a part of the MEXT-commissioned project titled “Development of environmental technology using nanotechnology.”
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Diffusion and remote detection of hot-carriers in graphene

In a new article published in ("Hot-Carrier Seebeck Effect: Diffusion and Remote Detection of Hot Carriers in Graphene"), ICN2 researchers led by ICREA Prof Sergio O. Valenzuela have investigated hot carrier propagation across graphene using an electrical nonlocal injection/detection method. The results create new opportunities for nanoscale bolometry and calorimetry and could have a strong impact in the performance of conventional graphene devices. Diffusion and Remote Detection of Hot-Carriers in Graphene Due to the weak electron-phonon coupling in graphene, 2D Dirac massless carriers can present a much more elevated temperature than the graphene lattice. Such hot carriers propagate over long distances resulting in novel thermoelectric and optoelectronic phenomena. The research, led by ICREA Prof Sergio O. Valenzuela, Group Leader of the Physics and Engineering of Nanodevices Group and Dr. Juan F. Sierra, Juan de la Cierva postdoctoral researcher, is focused on hot-carrier propagation across monolayer graphene using a novel electrical method in a device with multiple metal leads. Hot carriers are generated locally by an electrical current, diffuse away from the injection point and are detected electrically in a remote voltage probe by measuring the thermoelectric voltage. The relationship between the voltage and the dissipated Joule power in the injector is then studied. At high temperatures, the voltage is proportional to the power, as in ordinary thermoelectric experiments using an external heater. However, this simple relationship is lost as the temperature decreases, which is demonstrated to represent a fingerprint of hot-carrier dominated thermoelectricity. The measurement scheme allows researchers to evaluate the characteristic cooling length for hot-carriers, which is a key parameter for the development of high-speed graphene based devices. This fact, apart from having a strong impact the performance of conventional graphene devices, creates new opportunities for nanoscale bolometry and calorimetry.
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