Scientists unveil key to increasing efficiency in thin-film solar cells

Sample preparations and FIB etched samples. (A) Sample preparation procedures of the flexible CZTSSe device and FIB-etched samples. Credit: Carbon Energy.

A team of researchers has made significant strides in understanding how solar cells convert sunlight into electricity more efficiently.

Their latest findings, published in the journal Carbon Energy, focus on kesterite thin-film solar cells, which are known for their cost-effectiveness and use of readily available materials like copper, zinc, and tin.

Despite these advantages, the efficiency of kesterite solar cells has been relatively low.

This new research could change that, paving the way for more effective green energy solutions.

Solar cells work by absorbing sunlight and converting it into electrical energy.

This process involves the creation of electrons and holes within the solar cell material, which need to separate effectively to generate electricity.

However, inefficiencies often arise when these electrons and holes recombine prematurely, leading to lost potential energy.

The study conducted by researchers, including Kee-jeong Yang, Dae-hwan Kim, and Jin-gyu Kang from the Division of Energy & Environmental Technology at DGIST, used advanced scanning probe microscopy techniques.

This method allowed them to observe how electrons and holes behave within the solar cell’s light-absorbing layer, both within and between the material’s crystals.

Their observations revealed that the energy levels at the crystal interfaces — where the crystals meet — are higher than within the crystals themselves.

This difference in energy levels helps the electrons move more freely at these interfaces, which is crucial for improving the flow of electrical current through the solar cell.

However, the team also discovered that defects at these interfaces can cause the electrons and holes to recombine, which is detrimental to the cell’s efficiency.

To combat this, the researchers suggest that the light-absorbing layer should be uniformly created with higher energy levels at the interfaces than within the crystals.

They propose using elemental doping—a process of adding small amounts of other elements—to achieve this. Such adjustments could significantly enhance the efficiency of kesterite thin-film solar cells.

Senior Researcher Kee-jeong Yang emphasized the importance of their methodology. Traditional approaches like atomic force microscopy have been limited to analyzing the surface of the light-absorbing layer.

This study, however, expands the capability to analyze the entire layer, providing a fuller understanding of how carrier behaviors (movements of electrons and holes) impact solar cell efficiency.

This breakthrough not only offers a path to better solar cell designs but also has implications for other technologies that rely on similar principles of energy conversion.

By improving how we manage electron and hole separation in solar cells, researchers are moving closer to more sustainable and efficient use of our solar resources.

Source: KSR.