A Supramolecular “Double‐Cable” Structure with a 129₄₄ Helix in a Columnar Porphyrin‐C₆₀ Dyad and its Application in Polymer Solar Cells

Abstract

Abstract A novel porphyrin‐C 60 dyad (PCD1) is designed and synthesized to investigate and manipulate the supramolecular structure where geometrically isotropic [such as [60]fullerene (C 60 )] and anisotropic [such as porphyrin (Por)] units coexist. It is observed that PCD1 possesses an enantiomeric phase behavior. The melting temperature of the stable PCD1 thermotropic phase is 160 °C with a latent heat (Δ H ) of 18.5 kJ mol −1 . The phase formation is majorly driven by the cooperative intermolecular Por–Por and C 60 –C 60 interactions. Structural analysis reveals that this stable phase possesses a supramolecular “double‐cable” structure with one p ‐type Por core columnar channel and three helical n ‐type C 60 peripheral channels. These “double‐cable” columns further pack into a hexagonal lattice with a = b = 4.65 nm, c = 41.3 nm, α = β = 90°, and γ = 120°. The column repeat unit is determined to possess a 129 44 helix. With both donor (D; Pro) and acceptor (A; C 60 ) units having their own connecting channels as well as the large D/A interface within the supramolecular “double‐cable” structure, PCD1 has photogenerated carriers with longer lifetimes compared to the conventional electron acceptor [6,6]‐phenyl‐C 61 ‐butyric acid methyl ester. A phase‐separated columnar morphology is observed in a bulk‐heterojunction (BHJ) material made by the physical blend of a low band‐gap conjugated polymer, [poly[2,6‐(4,4‐bis‐(2‐ethylhexyl)‐4 H ‐cyclopenta [2,1‐b;3,4‐b′]‐dithiophene)‐ alt ‐4,7‐(2,1,3‐benzothia‐diazole)] (PCPDTBT), and PCD1. With a specific phase structure in the solid state and in the blend, PCD1 is shown to be a promising candidate as a new electron acceptor in high performance BHJ polymer solar cells.