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-2 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(sc) of 24.9 mA cm(-2) and a PCE of 15.4%. Our work demonstrates a new way to tune the photoelectronic properties of the "Y-series" NFAs.