Organic semiconductors enable the fabrication of a range of lightweight and mechanically flexible optoelectronic devices. Most organic semiconductor lasers, however, have remained rigid until now, ...predominantly due to the need for a support substrate. Here, we use a simple fabrication process to make membrane-based, substrate-less and extremely thin (<500 nm) organic distributed feedback lasers that offer ultralow-weight (m/A<0.5 gm
) and excellent mechanical flexibility. We show operation of the lasers as free-standing membranes and transfer them onto other substrates, e.g. a banknote, where the unique lasing spectrum is readily read out and used as security feature. The pump thresholds and emission intensity of our membrane lasers are well within the permissible exposures for ocular safety and we demonstrate integration on contact lenses as wearable security tags.
Organic optoelectronic devices combine high-performance, simple fabrication and distinctive form factors. They are widely integrated in smart devices and wearables as flexible, high pixel density ...organic light emitting diode (OLED) displays, and may be scaled to large area by roll-to-roll printing for lightweight solar power systems. Exceptionally thin and flexible organic devices may enable future integrated bioelectronics and security features. However, as a result of their low charge mobility, these are generally thought to be slow devices with microsecond response times, thereby limiting their full scope of potential applications. By investigating the factors limiting their bandwidth and overcoming them, we demonstrate here exceptionally fast OLEDs with bandwidths in the hundreds of MHz range. This opens up a wide range of potential applications in spectroscopy, communications, sensing and optical ranging. As an illustration of this, we have demonstrated visible light communication using OLEDs with data rates exceeding 1 gigabit per second.
Hybrid perovskite materials have considerable potential for light emitting devices such as LEDs and lasers. We combine solution processed CH
NH
PbI
perovskite with UV nanoimprinted polymer gratings ...to fabricate distributed feedback (DFB) lasers. The lead acetate deposition route is shown to be an effective method for fabricating low-loss waveguides (loss coefficient ~6 cm-1) and highly compatible with the polymer grating substrates. The nanoimprinted perovskite exhibited single-mode band-edge lasing, confirmed by angle-dependent transmission measurements. Depending on the excitation pulse duration the lasing threshold shows a value of 110 μJ/cm2 under nanosecond pumping and 4 μJ/cm2 under femtosecond pumping. We demonstrate further that this laser has excellent stability with a lifetime of 10
pulses.
Abstract
The strong nonlinearities of exciton-polariton condensates in lattices make them suitable candidates for neuromorphic computing and physical simulations of complex problems. So far, all room ...temperature polariton condensate lattices have been achieved by nanoimprinting microcavities, which by nature lacks the crucial tunability required for realistic reconfigurable simulators. Here, we report the observation of a quantised oscillating nonlinear quantum fluid in 1D and 2D potentials in an organic microcavity at room temperature, achieved by an on-the-fly fully tuneable optical approach. Remarkably, the condensate is delocalised from the excitation region by macroscopic distances, leading both to longer coherence and a threshold one order of magnitude lower than that with a conventional Gaussian excitation profile. We observe different mode selection behaviour compared to inorganic materials, which highlights the anomalous scaling of blueshift with pump intensity and the presence of sizeable energy-relaxation mechanisms. Our work is a major step towards a fully tuneable polariton simulator at room temperature.
In this paper we demonstrate a novel optical receiver for visible light communications that combines a fluorescent antenna and a silicon photomultiplier (SiPM). The fluorescent antenna is configured ...in a slab geometry to collect and absorb an incoming optical data signal, and to waveguide the resulting fluorescence to an edge where it is detected by the SiPM. The antenna incorporates the fluorophore, pentafluorene, selected for its very high bandwidth of 245 MHz, high photoluminescence quantum yield of 90%, and emission spectrum that matches the wavelengths most efficiently detected by the SiPM. The performance of a receiver, comprising the fluorescent antenna and a J-series 30020 SiPM manufactured by ON Semiconductor, was assessed in a 30 cm data link with a 405 nm GaN laser diode transmitter, both in the dark and under 500 lux of ambient white light. The fluorescent antenna successfully rejects ambient light by a factor of 20, limited by extrinsic scattering in the thin film. Using on-off-keying with decision feedback equalization, a maximum data rate of 1.4 Gbps was demonstrated in 500 lux of ambient light. Using the pentafluorene antenna plus a BG3 filter, provides a 200 fold suppression of ambient light, and can increase the data rate of the receiver at low signal powers by up to a factor of 2. When operating in ambient light the composite receiver requires only 2.5 times more signal power than when it operates in the dark, with this power penalty reducing to a factor of 1.2 at 1 Gbps.
Conspectus One of the most desirable and advantageous attributes of organic materials chemistry is the ability to tune the molecular structure to achieve targeted physical properties. This can be ...performed to achieve specific values for the ionization potential or electron affinity of the material, the absorption and emission characteristics, charge transport properties, phase behavior, solubility, processability, and many other properties, which in turn can help push the limits of performance in organic semiconductor devices. A striking example is the ability to make subtle structural changes to a conjugated macromolecule to vary the absorption and emission properties of a generic chemical structure. In this Account, we demonstrate that target properties for specific photonic applications can be achieved from different types of semiconductor structures, namely, monodisperse star-shaped molecules, complex linear macromolecules, and conjugated polymers. The most appropriate material for any single application inevitably demands consideration of a trade-off of various properties; in this Account, we focus on applications such as organic lasers, electrogenerated chemiluminescence, hybrid light emitting diodes, and visible light communications. In terms of synthesis, atom and step economies are also important. The star-shaped structures consist of a core unit with 3 or 4 functional connection points, to which can be attached conjugated oligomers of varying length and composition. This strategy follows a convergent synthetic pathway and allows the isolation of target macromolecules in good yield, high purity, and absolute reproducibility. It is a versatile approach, providing a wide choice of constituent molecular units and therefore varying properties, while the products share many of the desirable attributes of polymers. Constructing linear conjugated macromolecules with multifunctionality can lead to complex synthetic routes and lower atom and step economies, inferior processability, and lower thermal or chemical stability, but these materials can be designed to provide a range of different targeted physical properties. Conventional conjugated polymers, as the third type of structure, often feature so-called “champion” properties. The synthetic challenge is mainly concerned with monomer synthesis, but the final polymerization sequence can be hard to control, leading to variable molecular weights and polydispersities and some degree of inconsistency in the properties of the same material between different synthetic batches. If a champion characteristic persists between samples, then the variation of other properties between batches can be tolerable, depending on the target application. In the case of polymers, we have chosen to study PPV-type polymers with bulky side groups that provide protection of their conjugated backbone from π–π stacking interactions. These polymers exhibit high photoluminescence quantum yields (PLQYs) in films and short radiative lifetimes and are an important benchmark to monodisperse star-shaped systems in terms of different absorption/emission regions. This Account therefore outlines the advantages and special features of monodisperse star-shaped macromolecules for photonic applications but also considers the two alternative classes of materials and highlights the pros and cons of each class of conjugated structure.
Organic semiconductors for visible light communications Manousiadis, Pavlos P; Yoshida, Kou; Turnbull, Graham A ...
Philosophical transactions - Royal Society. Mathematical, Physical and engineering sciences/Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences,
04/2020, Volume:
378, Issue:
2169
Journal Article
Peer reviewed
Open access
Organic semiconductors are an important class of optoelectronic material that are widely studied because of the scope for tuning their properties by tuning their chemical structure, and simple ...fabrication to make flexible films and devices. Although most effort has focused on developing displays and lighting from these materials, their distinctive properties also make them of interest for visible light communications (VLCs). This article explains how their properties make them suitable for VLC and reviews the main uses that have been explored. On the transmitter side, record white VLC communication has been achieved by using organic semiconductors as colour converters, while direct modulation of organic light-emitting diodes is also possible and could be of interest for display-to-display communication. On the receiver side, organic solar cells can be used to harvest power and data simultaneously, and fluorescent antennas enable fast and sensitive receivers with large field of view. This article is part of the theme issue 'Optical wireless communication'.
Thin film chemical sensors are widely used in environmental and industrial applications due to their scalable fabrication and high sensitivity, however they often suffer from low specificity limiting ...their ability to discriminate between analytes. In this paper we analyse the influence of molecular diffusion and binding interactions on the optical response of thin film fluorescent chemical sensors. We use a computational model to calculate the dynamics of fluorescence quenching due to sorption and desorption of analyte molecules, and compare this with experimental measurements of a conjugated polymer sensor for nitroaromatic vapour. We find that to increase selectivity, such sensors should use thinner films, analyses should concentrate on the recovery dynamics, and sensor materials should be chosen to provide sensor-analyte combinations where diffusion is hindered by strong sensor-analyte binding interactions.
An analytical model was developed for thin film chemical sensors which provides insight into the sensor dynamics and potential strategies to develop chemical recognition.
We show that organic photovoltaics (OPVs) are suitable for high-speed optical wireless data receivers that can also harvest power. In addition, these OPVs are of particular interest for indoor ...applications, as their bandgap is larger than that of silicon, leading to better matching to the spectrum of artificial light. By selecting a suitable combination of a narrow bandgap donor polymer and a nonfullerene acceptor, stable OPVs are fabricated with a power conversion efficiency of 8.8% under 1 Sun and 14% under indoor lighting conditions. In an optical wireless communication experiment, a data rate of 363 Mb/s and a simultaneous harvested power of 10.9 mW are achieved in a 4-by-4 multiple-input multiple-output (MIMO) setup that consists of four laser diodes, each transmitting 56 mW optical power and four OPV cells on a single panel as receivers at a distance of 40 cm. This result is the highest reported data rate using OPVs as data receivers and energy harvesters. This finding may be relevant to future mobile communication applications because it enables enhanced wireless data communication performance while prolonging the battery life in a mobile device.
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