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.
Conductive ionenes were synthesized by integrating the electron donor dialkoxynaphthalene (DAN) with the electron acceptor naphthalene diimide (NDI) using the Menshutkin reaction. The crystallinity and morphology of the films of these polymers can be optimized by varying the DAN-to-NDI ratio. These ionenes show strong charge transfer from DAN to NDI, though absent conjugated backbones, affording self-doping polymers with enhanced π–π interactions and excellent electronic properties. This is the first example where an electron donor can dope the electron acceptor in nonconjugated polymers, opening a new avenue for designing efficient interlayer materials. These ionenes markedly modify the electrode interface and promote efficient interfacial self-doping to boost the performance of fullerene-based, non-fullerene-based, and ternary organic solar cells, affording high power conversion efficiencies over a wide range of interlayer thicknesses, from ∼8 to ∼40 nm, with a maximum efficiency of 17.05%.
We melted, annealed, and recrystallized ultrathin films of oriented polyethylene (PE) molecules prepared by melt-drawing. A large number of randomly oriented asymmetric leaf-shaped crystalline structures consisting of preferentially oriented lamellae were formed simultaneously, as observed by optical and atomic force microscopies. The structural arrangement within these leaf-shaped crystalline structures was identified by grazing incidence X-ray diffraction. These structures consisted of two distinct sections, both differing strongly from circular spherulites obtained by crystalizing an isotropic melt. Besides, regions containing groups of stacks of slightly inclined but well-aligned flat-on lamellae and regions of less orderly arranged edge-on lamellae were found. When increasing the annealing temperature and/or annealing time, a change in morphology from the leaf-shaped crystalline structures to spherulites with two symmetric "eyes" was observed. Intriguingly, the annealing times required for such a change in crystalline morphology were about four orders of magnitude longer than the longest bulk relaxation time (reptation time). Because the appearance of spherulites indicates that films became equilibrated and reached a state of an isotropic melt before recrystallization, we may conclude that oriented PE chains in ultrathin films possessed a long-term memory of the preparation-induced chain stretching. Considering that the morphology and relaxation kinetics of PE films depended appreciably on the substrate properties and film thickness, we conclude that the formation of asymmetric leaf-shaped crystalline structures was also affected by the interaction of PE chains with the substrate and spatial confinement. The present results may shed new light on slow relaxation and reorganization processes encountered when long-chain polymers became oriented during sample processing.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.