Conjugated polymers have sparked much interest as photocatalysts for hydrogen production. However, beyond basic considerations such as spectral absorption, the factors that dictate their photocatalytic activity are poorly understood. Here we investigate a series of linear conjugated polymers with external quantum efficiencies for hydrogen production between 0.4 and 11.6%. We monitor the generation of the photoactive species from femtoseconds to seconds after light absorption using transient spectroscopy and correlate their yield with the measured photocatalytic activity. Experiments coupled with modeling suggest that the localization of water around the polymer chain due to the incorporation of sulfone groups into an otherwise hydrophobic backbone is crucial for charge generation. Calculations of solution redox potentials and charge transfer free energies demonstrate that electron transfer from the sacrificial donor becomes thermodynamically favored as a result of the more polar local environment, leading to the production of long-lived electrons in these amphiphilic polymers.

The dissymmetric interaction between circularly polarised (CP) light and chiral molecules is central to a range of areas, from spectroscopy and imaging to next-generation photonic devices. However, the selectivity in...

Chiral molecules exist as pairs of nonsuperimposable mirror images; a fundamental symmetry property vastly underexplored in organic electronic devices. Here, we show that organic field-effect transistors (OFETs) made from the helically chiral molecule 1-aza[6]helicene can display up to an 80-fold difference in hole mobility, together with differences in thin-film photophysics and morphology, solely depending on whether a single handedness or a 1:1 mixture of left- and right-handed molecules is employed under analogous fabrication conditions. As the molecular properties of either mirror image isomer are identical, these changes must be a result of the different bulk packing induced by chiral composition. Such underlying structures are investigated using crystal structure prediction, a computational methodology rarely applied to molecular materials, and linked to the difference in charge transport. These results illustrate that chirality may be used as a key tuning parameter in future device applications

Circularly polarized (CP) electroluminescence has been demonstrated as a strategy to improve the performance of organic light emitting diode (OLED) displays. CP emission can be generated from both small molecule and polymer OLEDs (SM-OLEDs and PLEDs), but to date, these devices suffer from low dissymmetry factors (g-factor <0.1), poor device performance, or a combination of the two. Here, we demonstrate the first CP-PLED employing an inverted device architecture.

Efficient optical frequency mixing typically must accumulate over large interaction lengths as nonlinear responses in natural materials are inherently weak. This limits the efficiency of mixing processes due to the requirement of phase matching. Here we report efficient fourwave mixing (FWM) over micron-scale interaction lengths at telecommunications wavelength on silicon. We use an integrated plasmonic gap waveguide that strongly confines light within a nonlinear organic polymer. The gap waveguide intensifies light by nanofocusing it to a mode cross-section of a few tens of nanometers, thus generating a nonlinear response so strong that efficient FWM accumulates over wavelength-scale distances. This technique opens up nonlinear optics to a regime of relaxed phase matching, with the possibility of compact, broadband, and efficient frequency mixing integrated with silicon photonics.One Sentence Summary: Efficient wave mixing in plasmonic waveguides on silicon introduces a route to versatile non-resonant nonlinear optical devices with relaxed phase matching limitations. Main Text:Nonlinear optics, especially frequency mixing, underpins modern optical technologies and scientific exploration in quantum optics (1, 2), materials and life sciences (3, 4), and optical communications (5, 6). Four-wave mixing (FWM) is an important nonlinear frequency conversion technique used in photonic integrated circuits and telecommunications for signal regeneration (6), switching (7), phase-sensitive amplification (8), metrology (9), and entangled photon-pair generation (10). As a third order nonlinear effect, FWM is extremely sensitive to enhancement by the optical confinement of nanoplasmonic systems (11). For example, FWM has been demonstrated in a variety of metallic nanostructures including nano-antennas (12), rough surfaces (13), and at sharp tips (14). Nonetheless, efficient frequency conversion has remained elusive. While metals can be highly nonlinear and afford extreme optical localization, at telecommunications wavelengths only a small fraction of a plasmonic mode interacts with the metal and increasing this only exacerbates absorption. An alternative strategy is to incorporate low-loss nonlinear materials within nanoplasmonic systems (15, 16). Indeed, recent theoretical studies of FWM in plasmonic waveguides incorporating nonlinear polymers are promising (17).