Researchers at Martin Luther University Halle-Wittenberg (MLU) have unveiled a groundbreaking method to enhance solar cell efficiency by a factor of 1,000. This significant breakthrough was achieved by engineering crystalline layers of barium titanate, strontium titanate, and calcium titanate in an alternating lattice structure.

Their findings, published in the journal Science Advances, have the potential to transform the solar energy industry.

Currently, most solar cells are silicon-based, but their efficiency is inherently limited. This has driven researchers to investigate new materials like ferroelectrics, such as barium titanate, a compound composed of barium and titanium. Ferroelectric materials possess spatially separated positive and negative charges, resulting in an asymmetric structure that can generate electricity from light. Unlike silicon, ferroelectric crystals do not need a pn junction to create the photovoltaic effect, simplifying the production of solar panels. However, pure barium titanate has a low sunlight absorption rate, yielding a relatively small photocurrent. The new research demonstrates that layering different materials can significantly enhance solar energy yield.

Physicist Dr. Akash Bhatnagar from MLU’s Centre for Innovation Competence SiLi-nano explains, “The critical aspect is alternating a ferroelectric material with a paraelectric material. Although paraelectrics do not have separated charges, they can become ferroelectric under certain conditions, such as low temperatures or slight chemical modifications.”

Dr. Bhatnagar’s team discovered that the photovoltaic effect is significantly amplified when the ferroelectric layer is alternated not just with one, but with two different paraelectric layers. Yeseul Yun, a PhD student at MLU and the study’s first author, described the process: “We embedded the barium titanate between strontium titanate and calcium titanate. This was achieved by vaporizing the crystals with a high-power laser and redepositing them onto carrier substrates, creating a material consisting of 500 layers, each approximately 200 nanometers thick.”

When subjected to photoelectric measurements and irradiated with laser light, the new material produced a current flow up to 1,000 times stronger than that of pure barium titanate of similar thickness. This was despite the fact that the barium titanate proportion, the primary photoelectric component, was reduced by nearly two-thirds. “The interaction between the lattice layers seems to lead to much higher permittivity, meaning the electrons can flow much more easily due to the excitation by light photons,” explained Dr. Bhatnagar. The robustness of this effect was confirmed, as it remained nearly constant over a six-month period.

This innovative approach marks a significant advancement in solar cell technology, offering a pathway to highly efficient and scalable solar energy solutions. The research team’s work not only promises to enhance the performance of solar cells but also paves the way for future developments in photovoltaic materials.

By Impact Lab