Efficient organic solar cells based on a new "Y-series" non-fullerene acceptor with an asymmetric electron-deficient-core.

Herein, a new "Y-series" non-fullerene acceptor, Y21, bearing an asymmetric electron-deficient-core (DA'D) and fluorinated dicyanomethylene derivatives as flanking groups, was designed and synthesized for organic solar cell applications. Rather than being a perfect C symmetric traditional "Y-series" acceptor, Y21 possesses an electron-withdrawing unit (A') shifted from the center of DA'D, turning into an asymmetric molecular geometry. Photovoltaic devices based on PM6:Y21 can realize a high J of 24.9 mA cm and a PCE of 15.4%. Our work demonstrates a new way to tune the photoelectronic properties of the "Y-series" NFAs.