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Category: sustainability – Page 442

Multidimensional coherent spectroscopy reveals triplet state coherences in cesium lead-halide perovskite nanocrystals

Advanced optoelectronics require materials with newly engineered characteristics. Examples include a class of materials named metal-halide perovskites that have tremendous significance to form perovskite solar cells with photovoltaic efficiencies. Recent advances have also applied perovskite nanocrystals in light-emitting devices. The unusually efficient light emission of cesium lead-halide perovskite may be due to a unique excitonic fine structure made of three bright triplet states that minimally interact with a proximal dark singlet state. Excitons are electronic excitations responsible for the emissive properties of nanostructured semiconductors, where the lowest-energy excitonic state is expected to be long lived and hence poorly emitting (or ‘dark’).

In a new report now published in Science Advances, Albert Liu and a team of scientists in physics and chemistry at the University of Michigan, U.S., and Campinas State University, Brazil, used multidimensional coherent spectroscopy at cryogenic (ultra-cold) temperatures to study the fine structure without isolating the cube-shaped single . The work revealed coherences (wave properties relative to space and time) involving the triplet states of a cesium lead-iodide (CsPbI3) nanocrystal ensemble. Based on the measurements of triplet and inter-triplet coherences, the team obtained a unique exciton fine structure level ordering composed of a dark state, energetically positioned within the bright triplet manifold.

High efficiency wind turbine based on jet engine technology

Circa 2008

December 122008 Massachusetts-based FloDesign has developed a wind turbine that could generate electricity at half the cost of conventional wind turbines. The company’s design, which draws on technology developed for jet engines, circumvents a fundamental limit to conventional wind turbines. Typically, as wind approaches a turbine, almost half of the air is forced around the blades rather than through them, and the energy in that deflected wind is lost. At best, traditional wind turbines capture only 59.3 percent of the energy in wind, a value called the Betz limit.

Jet engine wind turbine

FloDesign is a spin-off from the aerospace company FloDesign based in Wilbraham, MA which recently raised $6 million in its first round of venture financing. Their turbine design surrounds its wind-turbine blades with a shroud that directs air through the blades and speeds it up, which increases power production. The shroud concept is based on the same principles as a high bypass jet engine design that is used by all commercial jet aircraft engines to reduce noise and significantly improve efficiency. The new design generates as much power as a conventional wind turbine with blades twice as big in diameter. The smaller blade size and other factors allow the new turbines to be packed closer together in the field compared to conventional turbines, increasing the amount of power that can be generated per acre of land.

BladeBUG Robots Clean Massive Wind Turbine Blades

There were the cleaners, with large padded feet, who were apparently polishing their way the whole length…’ — Arthur C. Clarke, 1972.

IceBot Antarctic (Planetary?) Robotic Explorers Made Of Ice ‘Some will combine in place to form more complicated structures, like excavators or centipedes.’ — Greg Bear, 2015.

Study: Robots Encourage Humans To Take Risks Not exactly Three Laws compliant.

IceBot Antarctic (Planetary?) Robotic Explorers Made Of Ice

BladeBUG Robots Clean Massive Wind Turbine Blades ‘There were the cleaners, with large padded feet, who were apparently polishing their way the whole length…’ — Arthur C. Clarke, 1972.

IceBot Antarctic (Planetary?) Robotic Explorers Made Of Ice ‘Some will combine in place to form more complicated structures, like excavators or centipedes.’ — Greg Bear, 2015.

Study: Robots Encourage Humans To Take Risks Not exactly Three Laws compliant.

A strategy to improve the efficiency and long-term stability of perovskite solar cells

Over the past few years, researchers have been trying to develop new designs for perovskite solar cells that could improve their performance, efficiency and stability over time. One possible way of achieving this is to combine 2-D and 3D halide perovskites in order to leverage the advantageous properties of these two different types of perovskites.

The two-dimensional crystal structure of 2-D halide perovskites is highly resistant to moisture; thus, it could help to increase the performance and durability of solar with a light-absorbing 3D halide perovskite layer. However, most of the strategies for combining 2-D and 3D halide perovskites proposed so far simply entail mixing these two materials together (e.g., mixing 2-D precursors with a solution-based 3D perovskite or reacting 2-D precursor solutions on top of a 3D perovskite layer).

Researchers at Seoul National University and Korea University have recently devised an alternative approach for creating solar cells that combine 2-D and 3D halide perovskites. This approach, outlined in a paper published in Nature Energy, could help to simultaneously improve both the efficiency and long-term stability of these cells.