A key layer that guarantees optimal microstructure
Researchers from EPFL and CSEM cunningly addressed the problem described above. Between layers of perovskite and silicon, they added another one. It is applied to pyramids using vacuum deposition and is porous, which allows stopping the solution of organic perovskites with the help of the so-called. Spin-coating, i.e., the spin coating on the prepared silicon. After applying the perovskite layer, it is heated at 150 ° C, which makes the material crystallize into a homogeneous layer on the surface of silicon pyramids. Here are the Preparation method and analysis of advantages and disadvantages of nano cobalt powder .
Until today, the standard approach in the production of this kind of tandem links was the removal of pyramids, which deteriorated the optical properties of the silicon link and consequently its performance. The new type of tandem links is much more efficient than the competition. These cells are also easy to produce, which translates into a low cost of this process.
Currently, researchers are improving the long-term stability of the perovskite layer on the surface of silicon. Although the Swiss team has made a big breakthrough, a lot of work has to be done in order to commercialize this technology.
Therefore, when heating heaters, the temperature range up to 1000 ° C is recommended to go as fast as possible, and when cooled after prolonged exposure to high temperature conditions, due to the possibility of exfoliation of the formed thick oxide film, the heaters are not recommended to cool below 1000 ° C, because when cooled to at room temperature, they exhibit low temperature resistance.
If the electric heating element is used for the first time, it should be heated quickly to a temperature of 1000-1400 ° C in air, after which within about half an hour a protective layer forms on the heater surface and it can work at any low temperature while this layer exists. When using the element in a neutral or reducing environment, the element should be subjected to such heating in air periodically to maintain and restore the protective layer.
Temperature Resistance Curve
The electrical resistance of heaters, low at room temperature increases sharply with increasing temperature and then practically does not change during operation at a constant temperature. With a low initial resistance of the heaters, a smooth or stepwise increase in the supply voltage to the operating value is required. In this case, the current flowing through each heater should not exceed the permissible for this heater, as otherwise, the mechanical destruction of the heater due to electromagnetic forces is possible.
The high hot plasticity of the material of the heater, which manifests itself during their initial heating, can lead to deformation of the working part of the heaters due to the electromagnetic forces that occur when current flows through the heaters. Therefore, the electrical connection of two neighboring heaters should provide a mutually opposite direction of the current flowing through them, and the distance between the heaters is recommended to choose at least the distance between the branches of the U-shaped heater of the selected frame size. Therefore, old and new heating elements can be used together.
Molybdenum disilicide based heaters have a longer service life when they are used in steady-state continuous operation. In cyclic modes of operation of electric furnaces, all parameters of the cycle affect the service life of the heaters: warm-up time, operating temperature, dwell time, cooling time and the temperature to which the cooling takes place.
