A team from the Martin Luther University Halle-Wittenberg (MLU) has taken an important step in researching solar cells. Combining the three crystal layers greatly increases the photovoltaic effect: by a factor of 1,000. This could make PV systems even more efficient.
A combination of materials with which solar cells can be coated make them a thousand times more efficient.
Photo: panthermedia.net/scalatore959
Rapid expansion is essential if the energy transition is to be successful renewable energy Absolutely necessary Systems that generate electricity more and more efficiently from renewable energy have been of decisive help. No wonder there is a lot of research in this area. A team of researchers from Martin Luther University Halle-Wittenberg is also examining the efficiency of solar module to increase significantly. Now they have achieved success with combining different crystals: they were able to use the so-called photovoltaic effect an increase of a factor of 1,000.
Who discovered the photovoltaic effect?
The photovoltaic effect converts sunlight into electricity. It was discovered 150 years ago. Physicist Edmund Alexandre Becquerel succeeded in this transformation for the first time in 1839, which was used primarily to measure exposure in photography.
Becquerel experimented with electrolytic cells in which he used an anode and cathode made of platinum. He could measure the current flowing between these electrodes. They found that the current in the light was slightly higher than in the dark. the basis of photovoltaic was discovered.
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More efficient solar cells thanks to photovoltaic effect with ferroelectrics
Silicon is currently the material most often used to manufacture solar cells. Disadvantages: The efficiency of silicon is limited. This is why research has been exploring alternatives for many years. Researchers are currently focusing on materials such as barium titanate, a mixed oxide of barium and titanium. These materials belong to the group of so-called ferroelectrics. “Ferroelectricity means that the material has spatially distinct positive and negative charges,” says Akash Bhatnagar, a physicist at the Center for Innovation Competence Silly-Nano at MLU.
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“Charge separation leads to a heterogeneous structure that enables electricity to be generated under light,” the physicist explains.
Since ferroelectric crystals do not require a so-called p-n junction for the photovoltaic effect, that is, no positively or negatively doped layers, this can make the production of solar modules quite easy. Silicon, on the other hand, needs this pn junction.
Material changes to make solar cells more efficient
However, pure barium titanate also has a definite disadvantage: it absorbs little sunlight and therefore produces a naturally low luminous flux in comparison. That’s why the research group experimented with a combination of different ingredients. Result: They make it possible to receive more energy from the Sun. “It is important that a ferroelectric material alternate with a paraelectric material. Although the latter has no distinct charge, it can become ferroelectric under certain conditions, such as low temperatures or slight modifications in chemical composition,” says Akash Bhatnagar report of.
As part of their tests, it has now emerged that the photovoltaic effect can be particularly enhanced if the ferroelectric layer is not combined with just one, but with two separate paraelectric layers alternately. “We embedded barium titanate between strontium and calcium titanate. To do this, the crystals are vaporized with a high-performance laser and re-deposited onto the carrier material. The material produced in this way has 500 layers. and it is about 200 nanometers thick,” explains Yesuk Yoon, a doctoral student at MLU and first author of the study.
Current flow in solar cells increased up to 1,000 times
The researchers tested their physical combination with laser light. They were really surprised by the result themselves. The current flow was 1,000 times stronger than that measured with pure barium titanate. With the new material combination, the scientists reduced the proportion of barium titanate as the main photoelectric part by about a third. “Obviously, the interaction of the lattice layers leads to a significantly higher permittivity—that is, electrons can flow more easily due to excitation by light photons,” Bhatgner says. And not only that: The researchers tested their new blend of ingredients over a period of six months. The effect was very strong and remained almost constant throughout the period.
The research group was supported for their study with funding from the Federal Ministry of Education and Research (BMBF), the German Research Foundation and the European Regional Development Fund (ERDF).
Where is solar energy most used?
Solar energy is considered to be kind to the environment as it does not produce air pollutants. Greenhouse gases are not released. Seasonal, day-dependent and meteorological fluctuations in energy content are harmful. Photovoltaics are less effective without direct sunlight. Therefore, the researchers made a real breakthrough.
Solar energy is used to generate electricity and heat the building. Solar energy can be used for both heating and feeding into the power grid. On average, individual solar cells generate an electrical voltage of 0.5 V – 0.6 V. To increase this voltage, the cells in the solar module are connected in series.
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