Researchers at Uppsala University in Sweden have developed the best possible version of a copper gallium selenide (CuGaSe) solar cell.2). By adding silver in the process of grain growth on the absorbent layer, they made the cell one of the highest efficiency for this type of device. The work has been published in a scientific journal RRL Solar.
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Swedish scientists are conducting extensive research on creating a stable, inorganic, and tandem solar cell. The lower unit in such a system shall be a layer of silicon, and the upper unit shall be a layer of selenide. Both parts complement each other in terms of absorbing solar radiation. Ultimately, the selenide cell must have a back contact, which is specifically designed for such assemblies.
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The main topic of this part of the research was to investigate how silver assists in the deposition of the absorbent layer on the selenide cell. Three stages of special evaporation made the layer filling factor much higher.
The researchers worked on a living model based on an insulating (intermediate) layer of tin and zinc oxide instead of the cadmium sulfide (CdS) traditionally used in this technique. The energy conversion efficiency of the cell was 11.2 percent. At first glance, that’s not much, but it is the highest value ever achieved on an inorganic selenide cell without an anti-reflective coating, the study authors admit.
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A benchmark score can be the result of several things. Not only did the silver help fill the absorbent layer with selenium grains more accurately, but also the change in the medium layer composition and temperature. More suitable coefficient values for higher deposition temperatures (about 650 °C) are shown.
However, the scientists’ task is far from over. Building a selenium-silicon tandem solar cell will still require several long months of work.