Chinese scientists achieve record-breaking 20% efficiency in single-junction organic solar cell

A team of scientists from Wuhan University of Technology in China improved the power conversion efficiency of an organic solar cell after fabricating a device using a newly designed non-fullerene acceptor.

In the research paper “Molecular interaction induced dual fibrils towards organic solar cells with certified efficiency over 20%,” published in the journal nature communications, the researchers say that improving the structure orders and optimizing the nanoscale morphology of organic semiconductors will play a critical role in achieving high efficiencies of organic solar cells. 

To test the theory, the scientists designed and synthesized a new non-fullerene acceptor, L8-ThCl, to act as the third component alongside a PM6:L8-BO host system. They say that adding L8-ThCl helped to enlarge and define the nanofibrils of polymer donors.

“We found that the well-arranged edge-on PM6 chains can be twisted into face-on orientation by the dipole–dipole interaction with L8-ThCl, and refined into nanofibrils with enhanced and denser π−π stacks,” the scientists explain in the paper. “Meanwhile, the good miscibility and intermolecular interactions between L8-BO and L8-ThCl in W and S-shaped packed dimers can effectively strengthen and regulate the packing networks of acceptors into one-dimension fibrils with high crystallinity.”

During testing, the team fabricated two devices – PM6:L8-ThCl/L8-BO:L8-ThCl and D18:L8-ThCl/L8-BO:L8-ThCl – that each recorded significantly boosted efficiencies, of 19.4% and 20.1% respectively.

The latter’s PCE was certified at 20%, which according to the scientists, is the highest certified efficiency reported for single-junction organic solar cells to date.

In the paper’s conclusion, the scientists say the strategy “offers an encouraging perspective on molecular aggregation manipulation of organic semiconductors to surpass the 20% milestone efficiency of organic solar cells.”

Earlier this year, a research team from Wuhan University of Technology and Central South University fabricated an ultra-thin organic solar cell with a bilayer hole transport layer that achieved an efficiency of 17%.