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Thiophene-phenylene co-oligomers (TPCOs) are among the most promising materials for organic light emitting devices. Here we report on record high among TPCO single crystals photoluminescence quantum yield reaching 60%. The solution-grown crystals are stronger luminescent than the vapor-grown ones, in contrast to a common believe that the vapor-processed organic electronic materials show the highest performance. We also demonstrate that the solution grown TPCO single crystals perform in organic field effect transistors as good as the vapor-grown ones. Altogether, the solution-grown TPCO crystals are demonstrated to hold great potential for organic electronics.

In recent years, monolayer organic field-effect devices such as transistors and sensors have demonstrated their high potential. In contrast, monolayer electroluminescent organic field-effect devices are still in their infancy. One of the key challenges here is to create an organic material that self-organizes in a monolayer and combines efficient charge transport with luminescence. Herein, we report a novel organosilicon derivative of oligothiophenephenylene dimer D2-Und-PTTP-TMS (D-2, tetramethyldisiloxane; Und, undecylenic spacer; P, 1,4-phenylene; T, 2,5-thiophene; TMS, trimethylsilyl) that meets these requirements. The self-assembled Langmuir monolayers of the dimer were investigated by steady-state and time-resolved photoluminescence spectroscopy, atomic force microscopy, X-ray reflectometry, and grazing-incidence X-ray diffraction, and their semiconducting properties were evaluated in organic field-effect transistors. We found that the best uniform, fully covered, highly ordered monolayers were semiconducting. Thus, the ordered two-dimensional (2D) packing of conjugated organic molecules in the semiconducting Langmuir monolayer is compatible with its high-yield luminescence, so that 2D molecular aggregation per se does not preclude highly luminescent properties. Our findings pave the way to the rational design of functional materials for monolayer organic light-emitting transistors and other optoelectronic devices.

Because of long-range order and high chemical purity, organic crystals have exhibit unique properties and attracted a lot of interest for application in solid-state lasers. As optical gain materials, they exhibit high stimulated emission cross section and broad tunable wavelength emission as similar to their amorphous counterpart; moreover, high purity and high order give them superior properties such as low scattering trap densities, high thermal stability, as well as highly polarized emission. As electronic materials, they are potentially able to support high current densities, thus making it possible to realize current driven lasers. This paper mainly describes recent research progress in organic semiconductor laser crystals. The building molecules, crystal growth methods, as well as their stimulated emission characteristics related with crystal structures are introduced; in addition, the current state-of-the-art in the field of crystal laser devices is reviewed. Furthermore, recent advances of crystal lasers at the nanoscale and single crystal light-emitting transistors (LETs) are presented. Finally, an outlook and personal view is provided on the further developments of laser crystals and their applications.

Organic semiconductors have many favourable and plastic-like optical properties that are promising for the development of low energy consuming laser devices. Although optically-pumped organic semiconductor lasers have been demonstrated since the early days of lasers, electrically-driven organic lasers have not been realized and have become one of the greatest challenges in the fields of physics, chemistry and materials science. This article highlights the recent progress in the development of electroluminescent devices, as well as new types of materials with the aim of realizing the first electrically-driven organic semiconductor laser.

We report a novel concept for multi-color light emission from an ambipolar organic single-crystal transistor using natural optical waveguides, the self-absorption effect, Davydov splitting and the unique alignment of the transition dipole moments. We used 9,10-bis(2,2-diphenylvinyl)-anthracene single crystals to produce blue and green light from identical single-crystal transistors. We also observed red light, which corresponds to the emission from in-gap states that are caused by impurities. Importantly, each of these different colors corresponds to a distinguishable light polarization, which enables us to tune the emission color by using a light polarizer. (C) 2013 Elsevier B. V. All rights reserved.

We demonstrate solution processable all-polymer based field-effect transistors (FETs) exhibiting comparable electron and hole mobilities. The semiconducting layer is a bulk heterojunction of poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (n-type polymer) and regioregular poly(3-hexylthiophene) (p-type polymer). These polymers form a type-II heterojunction as revealed by the faster photoluminescence dynamics of the blend compared to the pristine materials. An electron mobiliy of 4 x 10(-3) cm(2)/V s and a hole mobility of 2 x 10(-3) cm(2)/V s were extracted from the transfer characteristics of bottom contact FETs. The balanced mobilities suggest that the active layer is a fine network of the two components, as confirmed by atomic force microscopy phase images.

This research was financially supported by the European Research Council under the European Union's Seventh Framework Programme (FP/2007- 2013)/ERC Grant Agreement No. 306298 (EN -LUMINATE) and under the European Union’s Horizon 2020 Framework Programme (FP/2014- 2020)/ERC Grant Agreement No. 640012 (ABLASE) and by the EPSRC Programme Grant EP/P030017/1. L.T. thanks EPSRC for support through the CM -DTC (EP/L015110/1). Exciton-polaritons are quasiparticles with hybrid light–matter properties that may be used in new optoelectronic devices. Here, electrically pumped ultrastrongly coupled exciton-polaritons in a high-mobility donor–acceptor copolymer are demonstrated by integrating a light-emitting field-effect transistor into a metal-clad microcavity. Near-infrared electroluminescence is emitted exclusively from the lower polariton branch, which indicates efficient relaxation. A coupling strength of 24% of the exciton transition energy implies the system is in the ultrastrong coupling regime with a narrow and almost angle-independent emission. The lower polariton energy, which can be adjusted by the cavity detuning, strongly influences the external quantum efficiency of the device. Driving the transistors at ambipolar current densities of up to 4000 A cm−2 does not decrease the coupling strength or polariton emission efficiency. Cavity-integrated light-emitting field-effect transistors thus represent a versatile platform for polariton emission and polaritonic devices. Publisher PDF

Bottom-contact n-channel OFETs basedon spin-coated films of N,N'-1H,1H-perfluorobutyl dicyanoperylenediimide (PDI-FCN(2)) exhibit a saturation-regime mobility of 0.15 cm(2) V(-1) s(-1) in vacuum and good air stability. These performances are attributed to the high crystallinity and to the edge-on orientation promoted by the thermal treatment, as showed by confocal laser microscopy.

Bottom-contact n-channel OFETs basedon spin-coated films of N,N'-1H,1H-perfluorobutyl dicyanoperylenediimide (PDI-FCN(2)) exhibit a saturation-regime mobility of 0.15 cm(2) V(-1) s(-1) in vacuum and good air stability. These performances are attributed to the high crystallinity and to the edge-on orientation promoted by the thermal treatment, as showed by confocal laser microscopy.

Bottom-contact n-channel OFETs basedon spin-coated films of N,N'-1H,1H-perfluorobutyl dicyanoperylenediimide (PDI-FCN(2)) exhibit a saturation-regime mobility of 0.15 cm(2) V(-1) s(-1) in vacuum and good air stability. These performances are attributed to the high crystallinity and to the edge-on orientation promoted by the thermal treatment, as showed by confocal laser microscopy.

Because of long-range order and high chemical purity, organic crystals have exhibit unique properties and attracted a lot of interest for application in solid-state lasers. As optical gain materials, they exhibit high stimulated emission cross section and broad tunable wavelength emission as similar to their amorphous counterpart; moreover, high purity and high order give them superior properties such as low scattering trap densities, high thermal stability, as well as highly polarized emission. As electronic materials, they are potentially able to support high current densities, thus making it possible to realize current driven lasers. This paper mainly describes recent research progress in organic semiconductor laser crystals. The building molecules, crystal growth methods, as well as their stimulated emission characteristics related with crystal structures are introduced; in addition, the current state-of-the-art in the field of crystal laser devices is reviewed. Furthermore, recent advances of crystal lasers at the nanoscale and single crystal light-emitting transistors (LETs) are presented. Finally, an outlook and personal view is provided on the further developments of laser crystals and their applications.

Molybdenum disulfide (MoS2) has gained attention because of its high mobility and circular dichroism. As a crucial step to merge these advantages into a single device, we present a method that electronically controls and locates p-n junctions in liquid-gated ambipolar MoS2 transistors. A bias-independent p-n junction was formed, and it displayed rectifying I-V characteristics. This p-n diode could perform a crucial role in the development of optoelectronic valleytronic devices.

The bioelectrical signalling within neural networks has to be monitored in real-time and localized in space in order to unravel the mechanisms behind pathologies and diseases of the nervous systems. Organic materials have significant potential for bio-functional neural interfacing given that their "soft" nature offers better mechanical compatibility with the nerve tissues than conventional semiconductors, and their flexibility allows realization of the non-planar forms typically required for biomedical implants. The integration of living cells into organic semiconductors is an important step towards the development of bio-organic electronic transducers of cellular activity from neurons. Here, we report on the use and characterization of n-type perylene derivatives as a suitable interface platform for organic neuro-electronic devices. We demonstrate that primary neurons can adhere, grow and differentiate on a suitably engineered perylene-based field-effect transistor platform, while maintaining their firing properties even after a prolonged time of cell-culturing. It is noteworthy that the field-effect transistors preserve their electrical characteristics even after 10 days of incubation in cell culture media. These results validate n-type perylene derivatives as a suitable long-term interface platform for organic neuro-electronic devices, which is particularly relevant in view of the recently reported perylene-based field-effect transistor structure capable of providing bidirectional stimulation and recording of primary neurons.

The use of polymer dielectrics is an important step towards large-area, flexible, and low-cost electronics. In this letter, we study the effect of the polymer dielectrics polystyrene and parylene C on the charge transport properties of tetracene thin films in transistor configuration. By using polymer dielectrics, the tetracene hole mobility increased by more than one order of magnitude, up to 0.2 cm(2) V(-1) s(-1), as compared to bare silicon dioxide. We correlate this result to a favorable morphology of the tetracene films during the early stages of growth.

In this Article, we present a comprehensive study of organic field-effect transistors (OFETs) made of thin films of methyl, n-butyl, and n-hexyl end-substituted quaterthiophenes on a transparent substrate platform. This particular platform has been already used for organic light-emitting diodes (OLEDs) but rarely employed for OFETs. In perspective, this is a very promising route for the development of field-effect photonic applications such as organic light-emitting transistors (OLETs). A systematic characterization of the organic films has been made by means of atomic force microscopy (AFM) and X-ray diffraction (XRD) to correlate morphology, crystallinity and charge mobility to the alkyl chain length. In particular, a charge mobility value of 0.09 cm(2)/(V s) has been obtained in transparent OFETs with a large area channel for DH4T grown at room temperature. This mobility exceeds the one obtained on silicon-oxide substrates and is likely due to a more favorable interaction of the DH4T molecules with the PMMA layer employed as gate dielectric.

The use of carbon nanotube electrodes and new device geometries is enhancing the performance of organic light-emitting transistors.

We report a study of impurity effects on the electron transport of rubrene single crystals. A significant improvement of electron carrier mobility up to 0.81 cm(2)/V s is achieved by performing multiple purifications of single crystals and device aging inside an N(2)-filled glove box. The hole/electron mobility ratio obtained is in good agreement with the reported theoretical calculation, suggesting that the intrinsic electron transport of organic semiconductors is also exploitable in a manner similar to that of hole transport.

Bottom-contact n-channel OFETs basedon spin-coated films of N,N'-1H,1H-perfluorobutyl dicyanoperylenediimide (PDI-FCN(2)) exhibit a saturation-regime mobility of 0.15 cm(2) V(-1) s(-1) in vacuum and good air stability. These performances are attributed to the high crystallinity and to the edge-on orientation promoted by the thermal treatment, as showed by confocal laser microscopy.

In this letter we compare the transistor performances of two solution-processed perylene derivatives: N,N'-bis (n-octyl)- dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI8-CN(2)) and N,N'-1H,1H-perfluorobutyl dicyanoperylenediimide (PDIF-CN(2)). Perylenediimide nitrogen functionalization with perfluoroalkyl vs. alkyl chains improves the electron mobility of solution-processed organic field effect transistors (OFETs) by one order of magnitude. Time resolved spectroscopy allows attributing this increment to a higher degree of co-facial arrangement of the fluorinated molecules. This supramolecular arrangement enhances the pi-pi overlap leading to more efficient electron transport.

An ambipolar field-effect transistor (FET) based on a 1,3,6,8-tetraphenylpyrene (TPPy) single crystal, a highly photoluminescent material, has been successfully fabricated. Several kinds of metal electrodes have been employed to investigate the charge injection characteristics into the single-crystal FET. Hole and electron mobilities of 0.34 and 7.7 x 10(-2) cm(2)/(V center dot s) were achieved using Au and Ca electrodes, respectively. The ambipolar characteristic of this device gives a prospect for further development in light-emitting FET operation.

Organic FET transistors (OFETs) were fabricated on silicon substrates using pentacene as active organic layer and gold source and drain contacts. OFETs were used as test structures in order to study carriers photogeneration effect in organic layers. Photogeneration process was induced by exposing organic layers to a laser beam with 625 nm wavelength and an applied power varying in the range 10-40 mu W. As an effect of light exposure, OFET drain current is increased by three-to-six orders of magnitude, depending on devices operation conditions and their geometry. It is suggested that both electrons and holes generated in pentacene layer contribute to current increase. We put in evidence that electrons trapped at the pentacene-dielectric interface can act as a negative biased gate, demonstrating new operating capabilities of OFETs as well as light sensing functionality.