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Unicolored phosphor‐sensitized fluorescence (UPSF) is a dual emitting concept proposed for improving efficiencies and operational lifetimes of blue organic light emitting diodes (OLEDs). To overcome the limitations of the individual emitters, it uses a phosphorescent donor to sensitize a fluorescent acceptor. To quantify the potential of the concept, a multiscale model of a UPSF OLED is developed. It starts from atomistic morphologies, the rates of all processes on the available experimental data are parameterized, and the respective master equation is solved with the help of the kinetic Monte Carlo algorithm. The simulations show that the energy transfer between donor molecules is essential to reproduce the results of the time‐resolved photoluminescence experiment. The scope of the experiment is expanded by studying the effect of the acceptor concentration, as well as Förster and (parasitic) Dexter energy transfer from the donor to acceptor, on the characteristics of the UPSF OLED. The study shows that an appropriate material design can further improve efficiency by more than 30% and at the same time achieve radiative decay times below 0.02 µs, thus significantly extending OLED operational lifetime. [ABSTRACT FROM AUTHOR]

The increase of exposure to volatile organic compounds in general, and endocrine disruptors in particular, through daily healthcare consumer goods urgently calls for the development and commercialization of cheap and easy‐to‐use sensors to detect these molecules in air. Organic semiconductors (OSCs) promise the mass fabrication of cheap and flexible sensors, under the condition that the fabrication of functional thin films having the right morphology can be fully harnessed. Nanoporous morphologies are interesting in the field of gas sensing because they facilitate the diffusion of gas molecules to the active volume of organic field‐effect transistors (OFETs), at the vicinity of the gate dielectric. Nanoporous films of OSCs are, however, challenging to produce and to transfer into working sensors. Usage of nanoporous OSC films deposited on a sensitive 4‐tert‐butylcalix[6]arene gate dielectric as the active layer of an OFET‐based gas sensor is proposed here. The semiconducting molecules are self‐assembled into nanoporous films at the interface between air and water, allowing their transfer to practically any gas‐sensitive dielectric substrate. The OFET built on this film stack is used here to sense the presence of methyl 4‐hydroxybenzoate (methylparaben) in air at concentrations below 1 ppb. A nanoporous layer of organic semiconductor deposited on a sensitive calixarene‐based gate dielectric allows sub‐ppb detection of methylparaben in air. The nanoporous layer is interfacially self‐assembled, allowing its facile transfer on the sensitive dielectric. Its morphology guarantees the access of the methylparaben analyte to the zone where the sensitive dielectric is in contact with the organic semiconductor. [ABSTRACT FROM AUTHOR]

Poly(3‐hexyl‐thiophene‐2,5‐diyl) (P3HT) is one of the most commonly used materials in organic electronics, yet it is considered to be rather unattractive for organic field‐effect transistors (OFETs) due to its tendency to oxidize under aerobic conditions. Strong p‐doping of P3HT by oxygen causes high off‐currents in such devices opposing the desired high on/off‐ratios. Herein, a new application‐oriented method involving the recently developed immobilizable organic n‐dopant 2‐(2‐((4‐azidobenzyl)oxy)phenyl)‐1,3‐dimethyl‐2,3‐dihydro‐1H‐benzoimidazol (o‐AzBnO‐DMBI) is presented allowing to process and operate P3HT OFETs in air. The n‐dopants compensate oxygen doping by trapping generated free holes, thereby rediminishing OFET off‐currents by approximately two orders of magnitude. At the same time, field‐effect mobilities remain high in the order of up to 0.19 cm2 V−1 s−1. Due to the covalent attachment of the dopants to the host matrix after photochemical activation, a drift of the otherwise mobile ions within the device is prevented even at high operating voltages and, thus, hysteresis in the corresponding transfer characteristics is kept low. In this manner, the air instability of P3HT OFETs is successfully resolved paving an auspicious way toward OFET mass production. As the immobilization process employed here is nonspecific with respect to the host material, this strategy is transferable to other p‐type semiconductors. [ABSTRACT FROM AUTHOR]