No abstract

Six new molecules with donor−acceptor−acceptor (D−A−A) configuration bearing coplanar electron-donating dithieno[3,2-b:2′,3′-d]pyrrole (DTP) or aryl-substituted DTP as the D unit and the electron-withdrawing pyrimidine−dicyanovinylene or benzothiadiazole−dicyanovinylene as the A−A block are synthesized. The introduction of aryl groups (p-tolyl or p-anisolyl) onto the α position of DTP is found to greatly benefit the chemical stability and extend the molecular conjugation of the DTP-based D−A−A molecules. The observed broad absorption spectra and anisotropic molecular orientation in the thin films allow for these new D−A−A molecules to perform good capability of light harvesting. These new D−A−A donors are subject to the fabrication of vacuum-processed small-molecule organic solar cells (SMOSCs). The results showed that the structural modulation on the central A block (pyrimidine versus benzothiadiazole) as well as the terminal substitution (p-tolyl versus p-anisolyl)give an evident trade-off between the open circuit voltage (V oc ) and short circuit current density (J sc ) values. Among them, SMOSC-adopted D−A−A molecule TDPM composed of a p-tolyl terminal group and a D−A−A configuration of DTP− pyrimidine−dicyanovinylene as the electron donor combined with C 70 as the electron acceptor shows a J sc of 11.34 mA/cm 2 , a V oc of 0.94 V, and a fill factor (FF) of 0.52, giving a best power conversion efficiency (PCE) as high as 5.6%.