Imidazole-Functionalized Imide Interlayers for High Performance Organic Solar Cells

Imidazole-functionalized naphthalene diimide and perylene diimide were efficiently synthesized at low cost and used as versatile cathode interlayers in organic solar cells. These imidazole-functionalized small molecules show high electron affinity and conductivity and efficiently reduce the work function of air-stable metal electrodes, removing the energy barriers of electron transport in organic electronic devices. Compared to widely used amine-functionalized small-molecule cathode interlayers, the crystallinities of imidazole-functionalized molecules were moderately suppressed, affording good film-forming properties. The substitution of amine with the imidazole group is a simple and powerful strategy to improve both film morphology and charge transport of imide-based small-molecule interlayer materials. The imidazole-functionalized interlayers are compatible with numerous active layers in solar cells, affording high efficiencies over a wide thickness range from ∼5 nm to ∼33 nm, with a maximum efficiency of 17.98%, showing promising applications in organic electronics.