Perovskite Solar Cells with Enhanced Fill Factors Using Polymer-Capped Solvent Annealing

Perovskite solar cells have seen massive improvements over the last few years. But despite big increases in power conversion efficiency, fill factors – one of the important characteristics in need of optimization – have still hovered around 80 percent, limiting the capacity for solar energy.

Thanks to a team led by Associate Professor André D. Taylor, that fill factor has been pushed up to 85 percent. Using a polymer-capped solvent-annealing process, they enhanced open-circuit voltage without sacrificing short-circuit current, creating better perovskite cells with improved output and a longer lifespan than current models.

The research team included NYU Tandon Postdoctoral Research Associates Jaemin Kong and Jason A. Röhr, along with colleagues from Yale University, Brown University, Brookhaven National Laboratory and the Korea Research Institute of Chemical Technology, and received funding from several groups including the National Science Foundation and the Office for Naval Research. 

They found that during the solvent-annealing, the perovskite surface flattens and the perovskite grains agglomerate into micrometer-sized clusters having enlarged α-phase crystallites, while the δ-phase simultaneously disappears. The optimized structure enhances efficiency from 18.2 percent to 19.8 percent reliably, creating more stable and better solar cells.