Growth of organic crystalline thin films with strong second-order nonlinearity for integrated optics

We demonstrate the growth of highly nonlinear crystalline thin films of N-benzyl-2-methyl-4-nitroaniline (BNA) with a controllable crystal orientation. These films are obtained by crystallizing the material in a temperature gradient. Through second-harmonic generation experiments at a fundamental wavelength of 1550 nm, we found a second-order nonlinearity of (153 ± 70) pm/V. This greatly exceeds the value of 54 pm/V for LiNbO3, the benchmark nonlinear crystal. Moreover, the crystalline films are grown on amorphous substrates with processing temperatures not exceeding 115°C, making them suitable for back-end photonic integration on a CMOS chip. We envisage the growth of BNA crystalline films on silicon nitride photonic integrated circuits, where a strong second-order nonlinearity is lacking

Integration of highly crystalline C8-BTBT thin-films into simple logic gates and circuits

Highly crystalline organic thin films possess the charge carrier mobilities needed for high-performance, low-cost flexible electronics. However, only few reports exist that show the integration of these films into short-channel organic circuits. This work describes the integration of highly crystalline layers of the thermally and chemically fragile small molecule C8-BTBT. Thin films of this material are processed by a combination of zone-casting and homoepitaxial vacuum evaporation and display an average charge carrier mobility of 7.5 cm2/V in long channel transistors. The integration of these films into a circuit technology based on a 5 μm channel-length bottom-gate bottom-contact transistor topology results in inverters with gains up to 40 as well as a robust 19-stage ring oscillator. This circuit requires the simultaneous operation of 80 TFTs and displays a stage delay of 40 μs, resulting in an operating frequency of 630 Hz at an operating voltage of 10 V. With the help of circuit modelling, we quantify the relationship between the speed of ring oscillators and the contact resistance of individual transistors. Indeed, the successful integration of highly-crystalline layers with high intrinsic mobility stresses the need for advances in contact engineering

Growth of pentacene thin films by in-line organic vapor phase deposition

We present the extension of the organic vapor phase deposition technique to an in-line geometry, in which the sample travels underneath an elongated showerhead that sprays molecules transported by a stream of carrier gas. Highly uniform pentacene films are grown at web speeds of up to 2.1 m/min, equivalent to an average deposition rate of 105 angstrom/s in a static system. With transistor mobilities of up to 1.5 cm(2)/V s, these pentacene films are of high electrical quality. Importantly, this quality is conserved up to the highest deposition speeds. We discuss the relationships between in-line deposition rate, morphology and crystallinity of the deposited pentacene films and their electrical characteristics. (C) 2009 Elsevier B.V. All rights reserved.status: publishe

Predictive Model for the Meniscus-Guided Coating of High-Quality Organic Single-Crystalline Thin Films

A model that describes solvent evaporation dynamics in meniscus-guided coating techniques is developed. In combination with a single fitting parameter, it is shown that this formula can accurately predict a processing window for various coating conditions. Organic thin-film transistors (OTFTs), fabricated by a zone-casting setup, indeed show best performance at the predicted coating speeds with mobilities reaching 7 cm(2) V(-1) s(-1) .status: publishe

Predicting the optimal process window for the coating of single-crystalline organic films with mobilities exceeding 7 cm2/Vs

Organic thin film transistors (OTFTs) based on single crystalline thin films of organic semiconductors have seen considerable development in the recent years. The most successful method for the fabrication of single crystalline films are solution-based meniscus guided coating techniques such as dip-coating, solution shearing or zone casting. These upscalable methods enable rapid and efficient film formation without additional processing steps. The single-crystalline film quality is strongly dependent on solvent choice, substrate temperature and coating speed. So far, however, process optimization has been conducted by trial and error methods, involving, for example, the variation of coating speeds over several orders of magnitude. Through a systematic study of solvent phase change dynamics in the meniscus region, we develop a theoretical framework that links the optimal coating speed to the solvent choice and the substrate temperature. In this way, we can accurately predict an optimal processing window, enabling fast process optimization. Our approach is verified through systematic OTFT fabrication based on films grown with different semiconductors, solvents and substrate temperatures. The use of best predicted coating speeds delivers state of the art devices. In the case of C8BTBT, OTFTs show well-behaved characteristics with mobilities up to 7 cm2/Vs and onset voltages close to 0 V. Our approach also explains well optimal recipes published in the literature. This route considerably accelerates parameter screening for all meniscus guided coating techniques and unveils the physics of single crystalline film formation.status: publishe

Controlled nucleation and growth of single crystal organic semiconductor films on arbitraty substrates

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High-performance single-crystal organic transistors on flex

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Functional Pentacene Thin Films Grown by In-Line Organic Vapor Phase Deposition at Web Speeds above 2 m/min

We show in this paper that the organic vapor phase deposition technique can advantageously be extended to an in-line system, where a susceptor moves at a constant speed underneath an elongated showerhead. Highly uniform pentacene films are grown at web speeds of up to 2.1 m/min, equivalent to an average deposition rate of 105 angstrom/s in a static system. These pentacene films are of high electrical quality as proven by transistor mobilities of up to 1.5 cm(2) V-1 s(-1) and five-stage ring oscillators on foil that achieve a frequency of 24 kHz at a supply voltage of 20 V. (C) 2009 The Japan Society of Applied Physic

Influence of Solute Concentration on Meniscus-Guided Coating of Highly Crystalline Organic Thin Films

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Overlapping-Gate Organic Light-Emitting Transistors

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim A light-emitting transistor in which two gates, separated by an insulator, partially overlap in the center of the device is proposed. By accumulating charge carriers in dedicated transport layers, each gate independently controls charge injection into the emissive layer sandwiched between the transport layers. This structure combines the advantages of pinned light emission in the center of the channel, gapless charge transport into the recombination zone, and controlled balance of electron and hole concentration at the edges of the emissive layer for any chosen current density. High-performance devices with overlapping gates are demonstrated: Using a red fluorescent emitter, high external quantum efficiency (5.7%) is conserved up to the highest luminance (2190 cd m−2). A comprehensive optoelectronic device model is proposed that verifies the measured characteristics and confirms that efficiency is highest with balanced charge transport. This device topology opens perspectives in the development of bright thin film light sources driven at high current densities.status: publishe