Enhanced Performance and Stability of Ternary Organic Solar Cells Utilizing Two Similar Structure Blend Fullerene‐Free Molecules as Electron Acceptor

Abstract Fullerene‐free organic solar cells (OSCs) are fabricated using a blend of J61 polymer as donor and the blend of m‐3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexyl phenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′] dithiophene (ITIC) and ITIC‐Th as electron acceptor. The blend of m‐ITIC and ITIC‐Th as electron acceptor due to the similar lowest unoccupied molecular orbital energy levels and good compatibility among J61, m‐ITIC, and ITIC‐Th, are beneficial for the small energy barrier at the m‐ITIC:ITIC‐Th interface. Simultaneously, the ternary photoactive layer can maintain the optimize film morphology and beneficial to ensure effective suppression of charge recombination at the three kind materials interface. The power conversion efficiency of ternary OSCs achieves to 12.57% when the blend of m‐ITIC:ITIC‐Th (the ratio of m‐ITIC:ITIC‐Th is 40:60) as electron acceptor, with enhanced open‐circuit voltage (V_OC) of 0.91 V, short‐circuit current densities (J_SC) of 19.94 mA cm⁻², and fill factor of 69.6%. Moreover, the optimal ternary OSCs show enhanced thermal stability and photostability than the binary OSCs. This study indicates that the blend of m‐ITIC and ITIC‐Th as electron acceptor and J61 as donor is a promising strategy to fabricate high performance and stable OSCs.