Non-fused nonfullerene acceptors based on thieno[2',3':4,5]thieno[3,2-b] indole for efficient organic solar cells

Thieno[3,2-b]indole (TI) has attracted more and more attention in organic electronics. Herein, thieno[2',3':4,5] thieno[3,2-b]indole (TTI), as a tetracyclic derivative of TI, was been developed by fused another thiophene unit. Furtherly, two non-fused NFAs TTI-2F and TTI-2Cl based on TTI have been synthesized via simple and easy synthetic routes. TTI-2F and TTI-2Cl both exhibited excellent thermal stability, low optical bandgaps of-1.5 eV, nearly planar molecular geometries, and suitable energy levels. As a result, PM6:TTI-2F solar cells afforded a decent PCE of 10.67 %, with an VOC of 0.935 V, a J(SC) of 19.21 mA/cm(2) and a FF of 59.40 %, which was due to the suitable intermolecular interactions, higher HOMO energy level, better exciton dissociation, suppressed trapassisted recombination, and balanced charge carrier mobilities. As comparison, PM6:TTI-2Cl cell exhibited much lower PCE of 8.34 %. These results demonstrated that NFAs based on TTI are promising for industrialized organic photovoltaic applications due to the simple synthesis and decent photovoltaic performance.