Inkjet-printed vertically emitting solid-state organic lasers

In this paper, we show that Inkjet Printing can be successfully applied to external-cavity vertically-emitting thin-film organic lasers, and can be used to generate a diffraction-limited output beam with an output energy as high as 33.6 uJ with a slope efficiency S of 34%. Laser emission shows to be continuously tunable from 570 to 670 nm using an intracavity polymer-based Fabry-Perot etalon. High-optical quality films with several um thicknesses are realized thanks to ink-jet printing. We introduce a new optical material where EMD6415 commercial ink constitutes the optical host matrix and exhibits a refractive index of 1.5 and an absorption coefficient of 0.66 cm-1 at 550-680 nm. Standard laser dyes like Pyromethene 597 and Rhodamine 640 are incorporated in solution to the EMD6415 ink. Such large size " printed pixels " of 50 mm 2 present uniform and flat surfaces, with roughness measured as low as 1.5 nm in different locations of a 50um x 50um AFM scan. Finally, as the gain capsules fabricated by Inkjet printing are simple and do not incorporate any tuning or cavity element, they are simple to make, have a negligible fabrication cost and can be used as fully disposable items. This works opens the way towards the fabrication of really low-cost tunable visible lasers with an affordable technology that has the potential to be widely disseminated

Elaboration d'une expérience d'autodoublage de fréquence en solution de matériaux organiques multifonctionnels

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Inkjet-printed low-voltage organic thin-film transistors: Towards low-cost flexible electronics

International audienceIn this paper, we demonstrate how to enhance performances of Organic Thin-Film Transistors (OTFTs) made on flexible substrates by low-cost inkjet printing technique. Especially, we focus our attention on contact resistance to the channel in order to explain the differences in OTFT performances. For this, we first evaluate, on oxidized silicon wafer, the performances of several inkjetted couples of Organic Semiconductor(OSC)/Source and Drain (SD) electrodes compared to devices with evaporated metal SD. By this way, we show that inkjet printing is a suitable low-cost technique to dispense polymers and inorganic nanoparticules for the direct-writing of OTFTs. We obtain lower contact resistances when conducting polymer (PedotlPss) contacts the OTFT channel than evaporated metal (Au, Pt). Then, our strategy consists of printing the optimized OSC/SD electrodes couples on a multilayered cheap flexible substrate, coating with an ultrathin gate oxide (4nm), which allows low-operating for the printed OTFTs ([V] <3V). All these results pave the way towards flexible electronics applications. Copyright © 2007 Materials Research Society

Inkjet-printed polymer thin-film transistors: Enhancing performances by contact resistances engineering

International audienceIn this paper, we demonstrate how to enhance polymer thin-film transistors (PTFTs) performances made by low-cost inkjet printing technique. Indeed, in PTFTs, contact resistances between semiconducting conjugated polymers (SCPs) and Source and Drain (S&D) contacts may dominate the transport properties of such electronic devices. Here, we report measurements of these parasitic resistances for several couples of (i) SCPs, as active material, and (ii) electrodes, as S&D contacts, in bottom-contact inkjetted PTFTs. The differences in PTFT performances are discussed upon these contact resistance. For this, we evaluate the performances of several inkjetted couples of SCP/S&D compared to devices with evaporated metal-based S&D. By this way, we show that inkjet printing is a suitable low-cost technique to dispense polymers and inorganic nanoparticles for direct-writing of PTFTs. A significant reduction in the contact resistance RC was achieved when inkjetted Pedot: Pss-based S&D electrodes are used instead of evaporated metal-based S&D electrodes. The improved efficiency of charge carrier injection is assumed to be due to the formation of a p-doped interfacial layer at the interface between the SCP and the S&D electrodes. All these results pave the way towards flexible electronics applications by using inkjetted polymers both for electrodes and semiconducting active layer on flexible plastic substrate

Fake fingers in fingerprint recognition.

International audienc

Recent Progress in Flexible and Wearable All Organic Photoplethysmography Sensors for SpO2 Monitoring

Abstract Flexible and wearable biosensors are the next‐generation healthcare devices that can efficiently monitor human health conditions in day‐to‐day life. Moreover, the rapid growth and technological advancements in wearable optoelectronics have promoted the development of flexible organic photoplethysmography (PPG) biosensor systems that can be implanted directly onto the human body without any additional interface for efficient bio‐signal monitoring. As an example, the pulse oximeter utilizes PPG signals to monitor the oxygen saturation (SpO2) in the blood volume using two distinct wavelengths with organic light emitting diode (OLED) as light source and an organic photodiode (OPD) as light sensor. Utilizing the flexible and soft properties of organic semiconductors, pulse oximeter can be both flexible and conformal when fabricated on thin polymeric substrates. It can also provide highly efficient human‐machine interface systems that can allow for long‐time biological integration and flawless measurement of signal data. In this work, a clear and systematic overview of the latest progress and updates in flexible and wearable all‐organic pulse oximetry sensors for SpO2 monitoring, including design and geometry, processing techniques and materials, encapsulation and various factors affecting the device performance, and limitations are provided. Finally, some of the research challenges and future opportunities in the field are mentioned

Jet-printed electrodes and semiconducting oligomers for elaboration of organic thin-film transistors

International audienceA new oligomer of bithiophene and substituted fluorene has been successfully synthesized, exhibiting good FET performance. Our results show that devices can be obtained from inkjetted OTFTs and elaborated by direct writing without any particular pre-patterning or self-alignment techniques. We have also demonstrated the possibility to fabricate inexpensive OTFTs by direct writing paving the way toward using inkjet printing as the key technology for such applications in plastic electronics. The ease of this technique allows charts a clear path to flexible electronics. © 2006 Elsevier B.V. All rights reserved