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Ternary blend films, obtained by introducing a third component (a second acceptor as the third component) to a binary polymer solar cell (PSC), are a promising ternary strategy because the light absorption range, surface morphology, and charge carrier transport of the photoactive layer may be optimized, as can the energy level alignment between the donor and the acceptor. In this work, acceptors such as the short-wavelength-absorption polymer N2200 and the long-wavelength-absorption small molecule FOIC were combined with the donor PBDB-T-2F to construct ternary blends. The optimized ternary PSC could achieve a power conversion efficiency (PCE) of 13.98%, which is higher than the efficiencies of binary PSCs based on PBDB-T-2F:FOIC (12.65%) and PBDB-T-2F:N2200 (9.36%). The enhanced PCE of the ternary PSC is based on the high electron mobility, balanced charge transport, optimized surface morphology and charge carrier kinetics and the extended light absorption of the ternary photoactive layer, realized by adjusting the ratio of FOIC:N2200. Our results indicate that mixing a polymer acceptor into a binary photoactive layer to form a ternary blend photoactive layer is a valuable strategy for improving photovoltaic performance. Image 1 • Ternary PSCs were fabricated with F–N2200 as third component materials. • The improvement of charge dynamics process of ternary photoactive layer by ternary strategy. • The improved photon harvesting at the donor–blend acceptor interface. [ABSTRACT FROM AUTHOR]

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 (VOC) of 0.91 V, short‐circuit current densities (JSC) 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. [ABSTRACT FROM AUTHOR]