Solar panels have long aimed to convert as many photons as possible into usable energy. Researchers in chemistry, materials science, and electrical engineering have continuously worked to improve the efficiency of photovoltaic devices. However, current technologies are still limited by fundamental physical laws.
Recently, a breakthrough came from Penn University and Drexel University, who jointly developed a new solar cell model. This innovation promises not only to reduce manufacturing costs but also to enhance the efficiency of energy conversion. The traditional approach of photovoltaic cells involves absorbing light and exciting electrons, which then flow through a circuit to generate electricity. But this process requires two key materials: one that absorbs light and another that conducts electricity. Once an electron moves from the absorber to the conductor, it cannot return, limiting the system’s efficiency.
However, there exists a special class of materials that can generate electron flow without requiring a separate conductor. This phenomenon is known as the "photovoltaic bulk effect," distinct from the "interface effect" seen in conventional solar cells. Although discovered in the 1970s, these materials were not widely used because they only converted ultraviolet light—while most of the sun's energy lies in the visible and infrared spectrum.
Finding a material that exhibits the photovoltaic bulk effect could simplify production and help bypass the Shockley-Queisser Limit, which limits how much energy can be extracted from photons. In simple terms, the bandgap of a material determines the "value" of the energy it can capture. The lower the bandgap, the less energy is lost during the process.
To address this, researchers developed a new compound based on a "mother" material that reduces the bandgap, allowing for better absorption of visible light. By mixing and heating the materials, they created crystals with the desired properties. These perovskite-like structures have a unique crystal arrangement that allows for polarization and efficient charge movement.
This new material family has the potential to cover the entire solar spectrum, enabling a single material to behave like a multi-junction solar cell. It is also composed of low-cost, non-toxic elements, making it a promising alternative to traditional semiconductor materials.
The research, led by Andrew M. Rappe and Ilya Grinberg, was published in *Nature* and supported by multiple organizations, including the U.S. Department of Energy and the National Science Foundation. Contributions came from several students and researchers across both universities.
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