Synergistic Modifications of Side Chains and End Groups in Small Molecular Acceptors for High Efficient Non-Fullerene Organic Solar Cells

Two new acceptor-donor-acceptor (A-D-A) type non-fullerene acceptors, O-NTIC and O-NTNC, using hexacyclic naphthalene (cyclopentadithiophene) (NT) as the electron-donating unit, and dicycanovinylindan-1-one (INCN) or phenyl-fused dicycanovinylindan-1-one (NINCN) as the electron-deficient unit, respectively, are synthesized. From the perspective of synthesis easiness and cost, para-alkoxy-phenyl is used as side chains of the NT core. It is worth noting that the introduction of para-alkoxy-phenyl unit could tune the molecular energy levels and lift the open-circuit voltage (V-oc). Compared with O-NTIC, the introduction of extended end-groups NINCN leads to a more ordered packing structure, much red-shifted absorption and enhanced electron mobility of O-NTNC. With polymer PBDB-T as the donor, the organic solar cell (OSC) devices obtain a decent power conversion efficiency (PCE) of 9.1% for O-NTIC and much improved PCE of 11.0% for O-NTNC, respectively. Moreover, with a polythiophene derivative named PDCBT as the donor material, the PDCBT:O-NTNC based device exhibits a PCE of 10.0%, among the highest PCEs for PDCBT devices. These results indicate that O-NTNC has great potential on the application for high performance and low-cost OSCs, and the extended end group NINCN as well as para-alkoxy-phenyl side chain substituted core could be promising units for the design of materials with high performance.