Ambipolar charge transport and low threshold amplified spontaneous emission are observed in novel highly fluorescent liquid fluorene derivatives.

We demonstrate quasi-continuous-wave lasing in solvent-free liquid organic semiconductor distributed feedback lasers based on a blend containing a liquid 9-(2-ethylhexyl)carbazole host doped with a blue-emitting heptafluorene derivative. The liquid gain medium is bubbled with either oxygen or nitrogen in order to investigate the role of a triplet quencher such as molecular oxygen on the quasi-continuous-wave lasing properties of organic semiconductor lasers. The oxygenated laser device exhibits a low threshold of 2 μJ cm⁻², which is lower than that measured in the nitrogenated device and is independent of the repetition rate in a range between 0.01 and 4 MHz.

Arrays of gold nanocones have been fabricated by the nanotransfer printing (nTP) method and we have utilized these nanocones for field emission. By the nature of the printing, any shape of metal structure can be fabricated only at desired locations and a step-and-repeat process, which enables large-area fabrication, is possible. We demonstrate step-and-repeat printing with gold nanocone patterns occupying an area of 9 mm × 8 mm.

We demonstrate that blending fluorinated molecules in PEDOT:PSS hole transport layers (HTL) induces charge transfers which impact on both charge extraction and photogeneration within organic photovoltaic (OPV) devices. OPVs fabricated with modified HTL and two photoactive polymer blends led systematically to power conversion efficiencies (PCE) increases, with PTB7:PC₇₀BM blend exhibiting PCE of ∼8.3%, i.e. ∼15% increase compared to pristine HTL devices. A reduced device-to-device characteristics variations was also noticed when fluorinated additives were used to modify the PEDOT:PSS. Shading lights onto the effect of HTL fluorination, we show that the morphology of the polymer:PCBM blends remains surprisingly unaffected by the fluorinated HTL surface energy but that, instead, the OPVs are impacted not only by the HTL electronic properties (work function, dipole layer, open circuit voltage, charge transfer dynamic) but also by alteration of the complex refractive indices (photogeneration, short circuit current density, external quantum efficiencies, electro-optic modelling). Both mechanisms find their origin in fluorination induced charge transfers. This work points towards fluorination as a promising strategy toward combining both external quantum efficiency modulation and power conversion efficiency enhancement in OPVs. Charge transfers could also be used more broadly to tune the optical constants and electric field distribution, as well as to reduce interfacial charge recombinations within OPVs.

We present surface engineering of the top electrode in organic solar cells through soft contact lamination. A polymer conductor and a self-assembled monolayer material are utilized for the surface engineering of gold electrode in a polymer bulk-heterojunction solar cell. Approximately a threefold increase in the overall power conversion efficiency is shown to be realized with the surface engineering, which is made possible by the lamination.