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 ₆SubPc) as an alternative acceptor to C₆₀ 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 Cl₆SubPc versus SubNc, reduced recombination at the heterointerface, 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. The power conversion efficiency of a planar heterojunction solar cell based on boron subnaphthalocyanine chloride (SubNc) is improved from η_P = 2.8% to 4.4% by inserting diindenoperylene (DIP) at the anode and also to η_P > 6% by the use of a chlorinated subphthalocyanine (Cl ₆SubPc) as a non-fullerene acceptor material that increases open-circuit voltage, fill factor, and short-circuit current.