Isomer-free: Precise Positioning of Chlorine Induced Interpenetrating Charge Transfer for Elevated Solar Conversion

Summary The influence caused by the position of the chlorine atom on end groups of two non-fullerene acceptors ( ITIC-2Cl-δ and ITIC-2Cl-γ ) was intensely investigate. The single-crystal structures show that ITIC-2Cl-γ has a better molecular planarity and closer π-π interaction distance. More importantly, a 3D rectangle-like interpenetrating network is formed in ITIC-2Cl-γ and is beneficial to rapid charge transfer along multiple directions, while only a linear stacked structure could be observed in ITIC-2Cl-δ . The two acceptor-based solar cells show power conversion efficiencies over 11%, higher than that of the ITIC-2Cl- m -based device (10.85%). An excellent PCE of 13.03% is obtained by the ITIC-2Cl-γ -based device. In addition, the ITIC-2Cl-γ -based device also shows the best device stability. This study indicates that the chlorine positioning has a great impact on the acceptors, more importantly, the 3D network structure may be a promising strategy for non-fullerene acceptors to improve the PCE and stability of organic solar cells.