An A2–π–A1–π–A2-type small molecule donor for high-performance organic solar cells.

A new A₂–π–A₁–π–A₂-type small molecule denoted as BDD–IN was synthesized employing a strong electron-withdrawing unit, 3-bis(4-(2-ethylhexyl)-thiophen-2-yl)-5,7-bis(2-ethylhexyl)benzo[1,2:4,5-c′]-dithiophene-4,8-dione (BDD) as the central acceptor unit (A₁), thiophene-alkoxy benzene-thiophene as the π-bridge, and indenedione (IN) as the end-capped unit (A₂). An optimal power conversion efficiency (PCE) of 8.70% with a high open-circuit voltage (V_oc) of 0.965 V and a high fill factor (FF) of 72.3% was achieved. [ABSTRACT FROM AUTHOR]