A green solvent processable, self-doped N-annulated perylene butyl tetraester applied as a solar cell cathode interlayer

We report a new amino-bay-substituted, N-annulated perylene butyl tetraester (NH₂-PTEN-H) with application as a cathode interlayer in organic photovoltaic devices. Synthesis from the parent N-annulated perylene butyl tetraester is presented alongside comprehensive structural characterization. Density functional theory calculations on NH₂-PTEN-H and related analogues, both with and without N-annulation and amino-bay substitution, show that N-annulation locks the perylene core into a planar conformation even in the presence of a sterically demanding amino group. Steady-state optical spectra reveal intramolecular charge transfer characteristics and a large excited-state dipole moment. Solubility profiling establishes perylene butyl tetraesters as a highly soluble subclass of perylene dyes; NH₂-PTEN-H, in particular, dissolves readily in the green solvent ethyl acetate up to 168 mg mL⁻¹, enabling environmentally benign ink formulations. These inks were spin-coated into uniform thin films on quartz and studied, and electron paramagnetic resonance spectroscopy confirmed NH₂-PTEN-H as a paramagnetic species in the solid state. Utilized as a cathode interlayer in conventional organic photovoltaic devices, architectures containing NH₂-PTEN-H deliver power conversion efficiencies comparable to those using the benchmark cathode interlayer material PFN-Br.