Scientific Results

Interface Functionalities in Multilayer Stack Organic Light Emitting Transistors (OLETs)

Year: 2014

Authors: Capelli R., Dinelli F., Gazzano M., D’Alpaos R., Stefani A., Generali G., Riva M., Montecchi M., Giglia A., Pasquali L.

Autors Affiliation: CNR – Istituto Officina dei Materiali S.S. 14, km 163.5 in Area Science Park I-34012, Trieste, Italy; CNR- Istituto Nazionale di Ottica Area della ricerca di Pisa – Via G. Moruzzi 1 Località S. Cataldo 56124, Pisa, Italy; CNR – Istituto per la Sintesi Organica e la Fotoreattività via P. Gobetti 101 40129, Bologna, Italy; ETC S.r.l. – Via P. Gobetti 101 40129, Bologna, Italy; SAES Getters S.P.A. – Viale Italia 77 20020, Lainate, MI, Italy; Dipartimento di Ingegneria ‘Enzo Ferrari’ Università di Modena e Reggio Emilia Via Vignolese 905 41125, Modena, Italy; Department of Physics University of Johannesburg PO Box 524 Auckland Park 2006, South Africa

Abstract: Herein is described a multidisciplinary approach to understand the performance limitations of small molecule organic light emitting transistors (OLETs) based on a layered architecture, an innovative architecture potentially competitive with the state of the art and more flexible for spectral emission control. The processes of charge injection and field-effect transport at metal/organic and organic/organic interfaces are analysed using microscopic and spectroscopic techniques in coordination. Atomic force microscopy and ultrasonic force microscopy are employed to characterize the interface morphology and the initial growth stages of organic films where charge transport actually occurs. X-ray diffraction and near edge X-ray dichroic absorption with linearly polarised light allow to determine the unit cell packing and the molecular orientation at the active organic interfaces, as well as the amount of non-ordered domains. Moreover, chemical reactivity at the interfaces is measured by X-ray photoelectron spectroscopy. It is found that a strong reaction occurs at the metal-organic interfaces, with molecular fragmentation. Additionally, the transport properties strongly depend on the nature of the materials forming the organic stack. Specifically, amorphous conjugated films as bottom layers can promote an increased molecular disorder in the upper active layer, with a concomitant deterioration of the conduction properties.

Journal/Review: ADVANCED FUNCTIONAL MATERIALS

Volume: 24 (35)      Pages from: 5603  to: 5613

More Information: The authors kindly acknowledge E.T.C. s.r.l for the research funding and the Institute for Nanostructured Materials of the Italian Research Council (CNR-ISMN) of Bologna for providing the fabrication and electrical characterization of devices at the basis of the work here reported. Part of the experiments were carried out in proposal 20120153 at ELETTRA.
KeyWords: THIN-FILM TRANSISTORS; FIELD-EFFECT TRANSISTORS; PENTACENE TFT; BEAR BEAMLINE; EFFICIENCY; INJECTION; THIOPHENE; PHOTOEMISSION; DERIVATIVES; BRIGHTNESS

DOI: 10.1002/adfm.201400877

Citations: 8
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English