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.

Large-area anisotropic P(NDI2OD-T2) films are produced by epitaxial crystallization on a highly oriented polyethylene substrate, which display anisotropic mobility, conductivity and thermoelectric performance after doping N-DMBI.

Although non-fused ring electron acceptors (NFREAs) have received increasing attention due to their relatively low synthetic costs, the achievement of high efficiencies strongly depends on tedious pre-or/and posttreatments to refine the active layers, which in turn greatly increase fabrication complexity and expense of organic solar cells (OSCs). Nowadays most of the available as-cast devices based on NFREAs are below 12% efficiencies. Herein, phenylalkyl category side groups (CnPh) are employed to construct new NFREAs named BOR-CnPh (n = 3, 4, and 6), which exhibit inherently decent molecular aggregation and thus exclude additional treatments from device fabrication. The modified alkyl spacers of CnPh side groups not only trigger different aggregation of the acceptors, but also regulate the interaction conformations of donor (D) and acceptor (A), and thus D/A interactions. Encouragingly, the pristine PBDB-T:BOR-C4Ph blend delivers intrinsic fibrous networks with dominating face-on orientation, which yields an optimal efficiency up to 13.12%, and ranks as the highest value among as-cast OSCs based on NFREAs. This research provides a practical strategy to control molecular aggregations, interactions, and pristine heterojunction morphologies for easily available and high-performance organic photovoltaics.

Neat thin films of semiconducting polymers are attractive as efficient gain media toward optically pumped lasers. However, the optical loss and out-coupling of isotropic polymer thin films are far from being rationally regulated from the perspective of chain orientation and crystal form. Herein, we accomplished a simultaneous control of both chain orientation and crystal form in large-area highly ordered poly­(9,9-dioctylfluorene) (PFO) thin films through epitaxial crystallization. The well-arranged PFO lamellae naturally shape a low-loss, graded-index waveguide to provide spatially distributed optical feedback. Moreover, much more horizontally oriented dipoles significantly enhance the light out-coupling efficiency. Thus, the only 65 nm-thickness oriented PFO films demonstrate excellent amplified spontaneous emission with a low excitation threshold (7.1 μJ/cm2) and a narrow full width at half-maximum (2.2 nm) measured in the perpendicular direction of PFO chains. This strategy opens an effective pathway to prepare high-performance polymer thin-film lasers and electrically pumped polymer lasers.