Electroluminescence Properties of Poly(3-hexylthiophene)– Cadmium Sulfide Nanoparticles Grown In Situ C. Borriello, 1 S. Masala, 1 V. Bizzarro, 2 G. Nenna, 1 M. Re, 3 E. Pesce, 3 C. Minarini, 1 T. Di Luccio 1 1 Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile (ENEA), Unita ` Tecnica Tecnologie Portici Laboratorio Nanomateriali e dispositivi (UTTP-NANO) Centro Ricerche Portici, Piazzale E. Fermi, 80055 Portici (Napoli), Italy 2 Ingegneria dei Materiali polimerici e compositi e Strutture (IMAST), Piazzale E. Fermi, 80055 Portici (Napoli), Italy 3 Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile (ENEA), Unita ` Tecnica Tecnologie Materiali Brindisi, Laboratorio Materiali Compositi e Nanostrutturati (UTTMATB-COMP), Centro Ricerche Brindisi, SS7 Appia Km 713, 72100 Brindisi, Italy Received 28 April 2011; accepted 28 April 2011 DOI 10.1002/app.34774 Published online 11 August 2011 in Wiley Online Library (wileyonlinelibrary.com). ABSTRACT: In this work, a simple approach to prepare luminescent poly(3-hexylthiophene)–CdS nanocomposites to be employed in organic light emitting devices (OLED) devices is reported. The nucleation and growth of CdS nanoparticles were obtained by the thermolysis of a sin- gle Cd and S precursor dispersed in the polymer at three different temperatures of annealing: 240, 265, and 300  C. In this way, it was possible to compare the properties of nanocomposites containing nanoparticles with different sizes. X-ray diffraction and transmission electron micro- scopy analyses confirmed the formation of CdS nanopar- ticles and gave information about the size, distribution, and morphology of the nanoparticles; monodispersive and very small nanoparticles with diameters below 2.5 nm were obtained at 240  C. The application of such nanocomposites as emitting layers in OLED devices is discussed. Enhanced electrooptical properties were observed for the device containing the nanocomposite annealed at 240  C with respect to the pure polymer based device. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 3624–3629, 2011 Key words: conducting polymers; nanocomposites; nanoparticles INTRODUCTION Nanocomposites obtained by combining conducting polymers and semiconductor nanoparticles have so far attracted much interest for manifold applications, such as tunable luminous sources for field emission displays and electroluminescent devices. 1 Hybride nanocomposites have several advantages with respect to fully organic or fully inorganic systems. 2 As an example, polymers embedding semiconduct- ing nanoparticles combine their good processability, high transparency, and digital printing flexibility on a large scale with the unique optical properties of the nanoparticles. To date, a wide number of differ- ent semiconductor nanoparticles with a high quan- tum yield and a wide luminescence band like inor- ganic phosphors has been developed. The size and type of nanoparticles determine the emission color. 3 In particular, the combination of II–VI semiconduc- tor nanocrystals (or quantum dots) with conjugated polymers has been found to enhance the electrolumi- nescence (EL) properties of these materials and to improve the long-term stability, color tunability, and quantum efficiencies of electroluminescent devices based on such nanocomposites. 3 Nowadays, intensive research efforts have increas- ingly focused on the development of efficient elec- troluminescent hybrid nanoparticle–polymer materi- als for the fabrication of flexible organic light- emitting devices. One major difficulty is the control of the size, shape, and distribution of nanoparticles, which may influence the EL features. Usually, the introduction of nanoparticles within a polymer requires the use of surfactants to ensure their solu- bility in the conducting polymer solution. Neverthe- less, the presence of surfactants and ligands on the nanoparticle surface can limit the conductivity of nanocomposites. 4 Growing nanoparticles directly in a polymer matrix has been proposed as a valid method for guaranteeing an almost uniform distri- bution of nanoparticles and for avoiding the use of additional surfactants. This work shows the synthesis of conducting and luminescent hybrid nanocomposite materials by the nucleation and growth of CdS nanoparticles directly in the polymer poly(3-hexylthiophene) (P3HT). The purpose of our research was to improve the optoe- lectronic properties of the polymer through the enhancement of the luminescence intensity when the Correspondence to: C. Borriello (carmela.borriello@enea.it). Journal of Applied Polymer Science, Vol. 122, 3624–3629 (2011) V C 2011 Wiley Periodicals, Inc.