Synthetic Metals 147 (2004) 271–274 Electroluminescent behavior of polydiacetylene films Emilia Giorgetti a,∗ , Stefano Sottini a , Tommaso del Rosso b , Giancarlo Margheri b , Marina Alloisio c , Giovanna Dellepiane c a INSTM and Istituto di Fisica Applicata “Nello Carrara”, CNR, Via Panciatichi 64, 50127 Firenze, Italy b Istituto di Fisica Applicata “Nello Carrara”, CNR, Via Panciatichi 64, 50127 Firenze, Italy c INSTM, INFM and Dipartimento di Chimica e Chimica Industriale, Universit` a di Genova, Via Dodecaneso 31, I-16146 Genova, Italy Received 30 April 2004; received in revised form 14 June 2004; accepted 15 June 2004 Abstract We observed the electroluminescent behavior of films of the polydiacetylene poly[1,6-bis(3,6-dipalmitoyl-N-carbazolyl)-2,4-hexadiyne] (polyDPCHD) by preparing organic light-emitting diodes (OLED) based on a single emitting polymer layer. We measured their optical and electrical characteristics and obtained a typical power efficiency of 10 -6 . The observed rapid quenching of the electroluminescence was supposed to be related to the formation of charged traps enhanced both by local disorder of polymer chains and by current flow. © 2004 Elsevier B.V. All rights reserved. Keywords: Electroluminescent behavior; Organic light-emitting diodes; Polymer chains 1. Introduction Light-emitting diodes based on organic electrolumines- cent materials (OLEDs) have been actively studied since the late 1980s [1–3]. These devices offer big advantages with re- spect to their inorganic counterparts in terms of processabil- ity, cost reduction, colour tunability and low-voltage opera- tion. Several classes of organics have been tested up to now, with the aim of improving OLED characteristics, or satisfy- ing the demands of some specific application. However, to the authors’ knowledge, there are no reports in the literature about the electroluminescent behavior of polydiacetylenes. Polydiacetylenes have been studied extensively in the past 20 years, because of their unique -electronic properties, which produce large off-resonant third-order optical non-linearities in the telecommunications windows [4]. In general, they do not exhibit significant fluorescence, particularly in the solid state. For example, for one of them, the polyDPCHD-HS, a polycarbazolyldiacetylene with long hexadecylic chains on the 3,6 positions of carbazolyl substituents, the fluorescent ∗ Corresponding author. Tel.: +39 055 42351; fax: +39 055 410893. E-mail address: e.giorgetti@ifac.cnr.it (E. Giorgetti). behavior observed when dissolved in benzene, is quenched in other solvents, such as toluene, and in the solid state [5]. The quenching can be reasonably attributed both to a low- ering of the first symmetry forbidden level, the position of which is highly dependent on the molecular environment, and to an increase of electron–phonon coupling represented by the broadening of the electronic spectra of toluene solu- tions and of films. In contrast, poly[1,6-bis(3,6-dipalmitoyl- N-carbazolyl)-2,4-hexadiyne] (polyDPCHD), which is a sim- ilar compound having palmitoyl chains inserted at the 3,6 po- sitions of the carbazolyl groups [6,7], is strongly luminescent also in the solid state [8]. This observation stimulated us to investigate on the electroluminescence of polyDPCHD films. For this purpose, we prepared and characterized single-layer OLEDs based on polyDPCHD. 2. Experiments and discussion We prepared devices based on an emitting film of poly- DPCHD. Indium–tin-oxide (ITO) and Al films were used as anode and cathode, respectively. All the fabrication steps were carried out under clean room conditions. 0379-6779/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2004.06.029