A recent paper published in “Science Advances” magazine showed that the lattice arrangement of three layers of different ferroelectric crystals (in this case, barium titanate, strontium titanate, and calcium titanate) allows solar cells to The photovoltaic effect is increased by 1,000 times.

The research results come from Martin Luther University Halle-Wittenberg (MLU-Martin Luther University Halle-Wittenberg). The researchers rearranged the lattice of three different ferroelectric crystals (barium titanate, strontium titanate, and calcium titanate). The combination of ultra-thin layers of different materials produced a powerful solar photovoltaic effect, which could increase 1,000 times.

At present, most solar cells are of silicon-based structure. Studies have shown that the theoretical photoelectric efficiency of silicon-based solar energy is about 29%, which is now close to the limit. In order to further improve the photoelectric conversion efficiency, researchers have begun to try new materials such as gallium arsenide, laminated, multi-junction, perovskite, and ferroelectrics are one direction.

The difference between ferroelectric crystals and traditional silicon cells is that they do not require a pn junction to produce a photovoltaic effect, and do not need to create positive and negative doped layers in the cell. Researchers believe that ferroelectricity means that the material separates positive and negative charges in space. The charge separation leads to an asymmetric structure, and light energy is converted into electrical energy. This change can make the material easier to generate electricity.

Barium titanate is a kind of ferroelectric material, which is a mixed oxide made of barium and titanium. However, pure barium titanate does not absorb too much sunlight, and it generates relatively low photocurrent. MLU researchers have been experimenting with ultra-thin layers of barium titanate combined with different materials in an attempt to significantly increase battery power generation.

The researchers inserted barium titanate between strontium titanate and calcium titanate, adding a thin paraelectric layer to the battery. Although this layer has no separate charge, it can become a ferroelectric under certain conditions, such as at low temperatures or when the chemical structure changes slightly.

When the ferroelectric layer alternates with two different paraelectric layers, the interaction between the lattice layers seems to lead to a higher dielectric constant, photoelectrons can flow more easily, resulting in a stronger photovoltaic effect.

The researchers then irradiated the battery with laser light to test the new material, and the results surprised them. Compared with pure barium titanate of similar thickness, although the proportion of barium titanate is reduced by nearly two-thirds, three different materials are periodically arranged in the crystal lattice. Ferroelectric materials and paraelectric materials are used alternately, and the current intensity is as high as 1,000 times.

Compared with pure ferroelectrics, the layered structure shows higher power generation in all temperature ranges, and the crystals are also significantly more durable and do not require special packaging. Researchers will conduct further research to accurately find out the cause of the super photoelectric effect.

Source: Shanghai KINMACHI New Material Technology Service Number “Metal Material Expert”

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