Decreased Recombination Through the Use of a Non-Fullerene Acceptor in a 6.4% Efficient Organic Planar Heterojunction Solar Cell

An optimization of several aspects of planar heterojunction solar cells based on boron subnaphthalocyanine chloride (SubNc) as a donor material is presented. The use of hexachlorinated boron subphthalocyanine chloride (Cl-6 SubPc) as an alternative acceptor to C-60 allows for the simultaneous increase of the short-circuit current, fill factor, and open-circuit voltage compared to cells with fullerene acceptors. This is due to the complementary absorption of Cl-6 SubPc versus SubNc, reduced recombination at the hetero-interface, and improved energetic alignment. Furthermore, insertion of a thin diindeno[1,2,3-cd:1', 2', 3'-lm] perylene (DIP) layer at the anode results in a very significant 60% increase in photocurrent owing to reduced exciton quenching at the anode. The simultaneous improvement of all three solar cell parameters results in a power conversion efficiency of 6.4% for a non-fullerene planar heterojunction cell.