Near-Infrared Acceptors with Imide-Containing End Groups for Organic Solar Cells.

Near-infrared electron acceptors for organic solar cells (OSCs) mostly contain electron-withdrawing 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (IC) end groups, which can be modified by but limited to phenyl, thienyl, and naphthyl units with halogenated, methyl, and methyloxy substitution. In this work, we employed an imide-containing unit to construct a new IC end group, based on which a series of new electron acceptors were synthesized. The strong electron-deficient nature of imide units enables the new acceptors to show efficient intramolecular charge transfer and hence red-shifted absorption spectra compared to their IC counterparts. These new electron acceptors were applied to OSCs, providing efficiencies of over 17% with a low voltage loss of 0.52 eV. These results demonstrate that the new imide-containing end groups are promising fragments for the construction of near-infrared electron acceptors for high-performance OSCs.

Fluorescent BF2 complexes of pyridyl-isoindoline-1-ones: synthesis, characterization and their distinct response to mechanical force.

Three boron-pyridyl-isoindoline-1-one based dyes (B1, B2, and B3) with varied side groups were facilely synthesized. Detailed analyses were carried out concerning the crystal conformation, structure dependent photophysical properties and mechanochromic fluorescence (MCF). The MCF behaviours and solid-state emission were demonstrated to be correlated to the different side groups. Upon grinding, the emission of B1 exhibited little changes, whereas reversible MCF with a distinct colour change was observed for B2 and B3. B3 possessing sterically hindered triphenyl amine (TPA) groups showed the most prominent MCF effect. For instance, mechanical grinding resulted in a red-shift of fluorescence from 600 nm to 650 nm. The electronic and steric effects of the donating substituents were found to play important roles in modulating the intramolecular charge-transfer effect and intermolecular interactions. These sensitively and readily tunable mechano-responsive behaviors of the boron-pyridyl-isoindoline-1-one based dyes make them potential candidates for smart fluorescent materials.