Researchers at Martin Luther University Halle-Wittenberg achieved an increase in the photovoltaic effect of ferroelectric crystals by a factor of 10 by creating crystalline layers of barium titanate, strontium titanate and calcium titanate, which they alternately placed on top of one another.
Their findings, which were published in the journal Science Advances, could significantly increase the efficiency of solar cells.
In their paper, the researchers explained that most solar cells are currently silicon-based, which means that their efficiency is limited. This is what prompted them to examine the properties of barium titanate, a mixed oxide made of barium and titanium.
“Ferroelectric means that the material has spatially separated positive and negative charges,” Akash bhatnagar, co-author of the study, said in a media statement. “The charge separation leads to an asymmetric structure that enables electricity to be generated from light.”
Unlike silicon, ferroelectric crystals do not require a so-called pn junction to produce a photovoltaic effect; in other words, there is no positive doping layer. This makes the production of solar panels very easy.
Buttinger explained that pure barium titanate does not absorb much sunlight, resulting in a relatively low light current. However, recent research has shown that very thin layers of different materials significantly increase solar energy performance. "The important thing here is that a ferroelectric substance is converted to a paraelectric substance. If the latter does not have separate charges, but I can ferroelectric the condition, for example at a low temperature or when you change it chemically. " " The Bhatnagar research team discovered that the photovoltaic effect is greatly enhanced if the ferroelectric layer corresponds to more than one layer with two different parallectric layers. Therefore, they embed barium titanate between strontium titanate and calcium titanate. This was achieved by evaporating the crystals with a high-power laser and repositioning them on the carrier substrates. It created a material of 500 layers that is about 200 nanometers thick. When performing photoelectric measurements, new materials are irradiated with laser light. The result was unexpected: the current was up to 10 times stronger than that of pure barium titanate of similar thickness - and this would have dropped by two-thirds even if the ratio of barium titanate as the main photoelectric component was present. "It seemed that the lattice between the lattice had become much more permeable - in other words, the electrons could flow much more easily due to the excitation of light photons," Behtnagar said. The measurement also showed that this effect is very strong: the moon remained constant for six months. The scientist also said that more efforts should be made now to determine exactly what is highlighting the photoelectric effect. However, he is confident that the potential demonstrated by the new concept can be used for applications applicable to solar panels. "Layers show completely in all tail-related ranges than pure ferroelectrics. Crystals are also significantly more durable and require packaging.
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