A research team from the University of Michigan said they set a new efficiency record for color-neutral, transparent solar cells.

Instead of following the conventional silicon-based design, the team attained 8.1% efficiency and 43% transparency with an organic/carbon-based design. The cells carry a green tint, but it resembles the gray color on sunglasses and automobile windows.

According to lead researcher Stephen Forest, these organic solar cells are compatible with windows that cover the face of most buildings. The organic cells offer the winning combination of high efficiency and high transparency, which silicon doesn’t.

Usually, buildings with glass exteriors use a coating which not only reflects but also absorbs some light, in both visible and infrared spectrums, reducing brightness and heat within the structure. Transparent solar panels can redirect this light to generate energy and reduce the building’s load on the electric grid.

According to Yongxi Li, an assistant research scientist in electrical engineering and computer science, the new material and the structure of the device needed multiple simultaneous trade-offs to ensure- ample sunlight absorption, high voltage, high current, low resistance, and color-neutral transparency.

The organic compounds in the new material are engineered to be transparent in visible light and absorb the near-infrared light. The research team has also developed optical coatings to boost the power generated from infrared light and transparency in the visible light.

The color-neutral version of this device was made from an indium tin oxide electrode. When a sliver electrode was introduced in the device, it ramped up the efficiency to 10.8% with 45% transparency; however, the mild greenish tint of the device may not be acceptable in some window designs.

Older transparent solar cells roughly offer 2-3% light utilization efficiencies; meanwhile, indium tin oxide cell is rated at 3.5% and the silver version at 5%. Both versions can be manufactured using materials that are less toxic than older versions of transparent solar cells.

The research team now aims to improve the light utilization efficiency of 7% and the lifetime of the cell to 10 years.

Mercom had earlier reported on Australian scientists, led by members of the ARC Center of Excellence in Exciton Science, who had published a research paper stating that they have succeeded in producing semi-transparent perovskite solar cells that generate electricity. This breakthrough could allow for windows in buildings and automobiles to generate electricity.

Recently, the researchers at Iowa State University said they had come up with an innovative way to stabilize perovskite cells at high temperatures. They have developed a technique that has made the material more stable at higher temperatures.

Image Credit: University of Michigan