Near-infrared non-fullerene acceptors based on dithienyl[1,2-b:4,5-b’]benzodithiophene core for high performance PTB7-Th-based polymer solar cells

Abstract Two non-fullerene electron acceptors (BT-SFIC and BT-FIC) bearing a dithienyl[1,2-b:4,5-b’]benzodithiophene core were designed and synthesized. Due to the strong electron-withdrawing ability of fluorine atoms, these two non-fullerene acceptors both show near-infrared absorption around 900 nm, with a narrow bandgap of 1.44 and 1.39 eV for BT-SFIC and BT-FIC, respectively. BT-SFIC and BT-FIC have complementary absorption and matched energy level with PTB7-Th. PSCs based on PTB7-Th donor and these two acceptors both show good charge dissociation and collection, small charge recombination and good active layer morphology. However, BT-FIC bearing much more fluorine have much higher electron mobility. And the PSCs based on PTB7-Th: BT-FIC gives a maximum PCE of 10.10% with a V OC of 0.73 eV, a J SC of 21.28 mA cm −2 and an FF of 65%, which is among in the high-performance polymer organic solar cells based on PTB7-Th.