2-Dimensional cross-shaped tetrathienonaphthalene-based ladder-type acceptor for high-efficiency organic solar cells

AnNC-FICnonfullerene acceptor, using a didodecylnaphthodithiophene (NDT) embedded octacyclic ladder-type donorNC, had been described previously. In this work, a new cross-shapedTC-FICnonfullerene acceptor is designed by substitution of the NDT unit in theNCskeleton with a 2-dimensional didodecyltetrathienonaphthalene (TTN) unit. The 2-dimensionalTC pi-system with two vertically fused thiophenes strengthens the electron-donating ability, promotes pi-electron delocalization and enhances intramolecular donor-acceptor charge transfer and intermolecular pi-pi interactions. As a result,TC-FICshows more red-shifted and widened absorption compared to theNC-FICcounterpart. The PBDB-T:TC-FICdevice exhibits a higher efficiency of 11.6% which greatly outperformed the corresponding PBDB-T:NC-FICdevice with an efficiency of 7.52%. The dramatic 54% enhancement in efficiency is ascribed to the improved light-harvesting ability and enhanced charge mobilities which are benefited from the central 2-dimensionalTTNmoiety. By incorporatingPC(71)BMto improve absorption and electron transport, the ternary-blend PBDB-T : TC-FIC : PC(71)BMdevice (1 : 1 : 1 in wt%) achieves a highest PCE of 13.49% with an enhancedJ(sc)of 23.80 mA cm(-2), an FF of 64.4%, and aV(oc)of 0.88 V.