One of the bottlenecks in widespread implementation of sustainable energy technologies are highly efficient energy storage systems. Lithium-ion batteries (LIBs) are the prevailing solution for today’s electronic devices, from consumer gadgets to medical devices, electric vehicles, even satellites. The main reason for the domination of LIB technology in many application areas is that it has the highest electrical storage capacity with respect to its weight.
LIBs generally contain an energy capacity of 100–200 Wh/kg. This allows most electric cars to travel upwards of 300-400 kilometers on a single change. However, despite the high energy density of LIBs compared to other kinds of batteries, they are still around a hundred times less energy dense than gasoline (which contains 12700 Wh/kg by mass or 8760 Wh/L by volume). That means that gasoline-powered engines are gaining higher thermal efficiencies, allowing for fuel efficiencies upwards of 6-7 L/100km. On a 60-liter tank, this allows for more than 800-1000 km of range, easily doubling, or even tripling that of the average electric car.
Although LIBs are continuing to achieve higher energy densities, various research studies are indicating that max theoretical energy limits (estimated at 400-500 Wh/kg) are in sight.
The new method of making mixed halide-perovskites results in solar cells with improved stability and performance. The new method results in better control over perovskite crystallization rates. This means the crystal structure is more ordered, in part due to researchers understanding and taking advantage of the faster crystallization of bromide relative to iodide.
The result is a material with fewer defects and less halide migration and thus less segregation of the bromide and iodide. This in turn means uniform mixing of bromide and iodide across the material, which allows the material to absorb light evenly. The end result is that solar cells made using the new method will perform better under real-world conditions.
Typical halide perovskite solution deposition uses an anti-solvent drip procedure to initiate crystallization of the halide film. The standard anti-solvent method for producing bromide-iodide mixed halide perovskite films often leads to excessive defect formation (e.g., bromide vacancies) owing to the rapid crystallization of bromide vs. iodide-perovskite phases. Simulations show that halide migration is enhanced in the presence of a large population of halide vacancies. This limits the stability of bromide-iodide mixed halide perovskites under light and heat.
In comparison to the anti-solvent approach, the gentler gas-quench method better controls crystallization, first producing a bromide-rich surface layer that then induces top-down columnar growth to form a gradient structure with less bromide in the bulk than in the surface region. The anti-solvent method does not produce such a gradient structure.
In this study, researchers from the National Renewable Energy Laboratory, the University of Toledo, and the University of Colorado Boulder demonstrated that the gas-quench method also produces fewer bromide vacancies and results in materials with a higher quality opto-electronic performance. Solar cells made using the gas-quench method retain desirable light absorption properties and provide enhanced performance in the form of a higher charge carrier mobility, higher open circuit voltage, and enhanced stability.
Device miniaturization and a consequent increase in the heat and electromagnetic (EM) wave emission in the electronic systems make the simultaneous heat management and electromagnetic interference (EMI) shielding crucially important.
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