The majority of solar power in use across the world today is in solar farms, filled with rigid silicon-based solar panels. As solar power becomes more ubiquitous, it will spread beyond fixed panels to applications that require more flexibility and while flexible solar panels exist, they’re still less efficient than those silicon panels in solar farms. Research, like that ongoing at New York University’s (NYU’s) is aiming to change that.
Now, NYU’s Tandon School of Engineering has introduced a new method of improving the efficiency of flexible solar cells, which can be used in everything from solar panels to electric cars to backpacks. A method which the researchers, led by Tandon Professor André Taylor, contended could improve solar cells and expand their range of applications.
Taylor, whose research was published in Materials Today likened a solar cell to a sandwich, explaining that the work was on the outer layers, which he likened to the bread of the sandwich. “My group works on key parts of the ‘sandwich,’ such as the electron and hole transporting layers of the ‘bread,’ while other groups may work only on the ‘meat’ or interlayer materials,” Taylor said. “The question is: How do you get them to play together? The right blend of these disparate materials is extremely difficult to achieve.”
Many organic solar cells use fullerenes (spherical carbon molecules) to absorb light, but NYU’s research uses non-fullerenes, noting that they such molecules have proven inefficient at converting sunlight. Instead the researchers are using a squaraine molecule in a new way. It serves as a crystallizing agent.
“We added a small molecule that functions as an electron donor by itself and enhances the absorption of the active layer,” Taylor stated. “By adding this small molecule, it facilitates the orientation of the donor-acceptor polymer (called PBDB-T) with the non-fullerene acceptor, ITIC, in a favorable arrangement.”
The research also involved an energy transfer method borrowed from photosynthesis, a technology known as Förster resonance energy transfer (FRET). With the FRET solar cell, a new polymer and the non-fullerene blend with squaraine, the team produced an organic solar cell that converted more than 10 percent of solar energy into electricity.
“We expect that this crystallizing-agent method will attract attention from chemists and materials scientists affiliated with organic electronics,” said Yifan Zheng, lead author of the research and a former student of Taylor.
It’s still far below the capabilities of silicon solar but shows continued improvement for such single-junction polymer solar cells. "There are now newer polymer non-fullerene systems that can perform above 13 percent, so we view our contribution as a viable strategy for improving these systems," Taylor contended.Tweet