Fullerene–non-fullerene hybrid acceptors for enhanced light absorption and electrical properties in organic solar cells

Two fullerene–non-fullerene hybrid acceptors, IDTIC-PC₆₁BM (IP) and PC₆₁BM-IDTIC-PC₆₁BM (PIP), are synthesized by combining a non-fullerene acceptor, 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d’]-s-indaceno[1,2-b:5,6-b’]dithiophene (IDTIC), and a fullerene derivative, phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM). To evaluate the potential of these hybrid acceptors, we fabricate organic solar cells (OSCs) based on the four different acceptors (i.e. IP, PIP, IDTIC, and PC₆₁BM) and the same polymer donor (PBDB-T). In IP and PIP, the IDTIC moiety compensates for the poor light absorption of PC₆₁BM in the visible wavelength region, improving the short-circuit current density (J_SC) of the hybrid acceptor-based OSCs (11.9 → 13.1 mA cm⁻²). Meanwhile, the charge transport and recombination properties of the PBDB-T:IDTIC devices improve significantly after the substitution of IDTIC with IP or PIP, leading to a significant increase in the fill factor (0.54 → 0.68) as well as J_SC (11.8 → 13.1 mA cm⁻²) of the devices. Therefore, owing to the synergistic effect of the broad light absorption of IDTIC and efficient electron transport of PC₆₁BM, the hybrid acceptor-based OSCs show significantly higher power conversion efficiencies of 8.81% (PBDB-T:PIP) and 8.17% (PBDB-T:IP) than the PBDB-T:PC₆₁BM (7.62%) and PBDB-T:IDTIC (5.98%) OSCs. The results demonstrate the effectiveness of the hybrid acceptor design in overcoming the shortcomings of individual acceptors and improving their photovoltaic performance.