Synthesis and Characterization of Copper (I) Chloride (CuCl) Nanocrystals in Conductive Polymer for UV light Emitters
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1247-C04-21
Synthesis and Characterization of Copper (I) Chloride (CuCl) Nanocrystals in Conductive Polymer for UV light Emitters
M. M. Alam1*, F. Olabanji Lucas1, A. Cowley1, Karl Crowley2, S.Daniels1, K.V. Rajani1, P. J. McNally1 1
Nanomaterials Processing Laboratory, School of Electronic Engineering, Dublin City University, Dublin 9, Ireland. Corresponding author. E-mail: [email protected] 2 School of Chemical Science, National Centre for Research, Dublin City University, Dublin 9, Ireland *
ABSTRACT Intrinsic γ-Copper (I) Chloride is an ionic I-VII compound semiconductor material with relatively low conductivity. To fabricate an efficient electroluminescent device based on CuCl nanocrystals (NC) the conductivity of the CuCl NC film should be relatively high. In order to improve the conductivity of CuCl films, nanocrystals were embedded in a highly conductive polymer (Polyaniline) and deposited on glass substrates via the spin-coating method. The deposited films were heated at 140 o C for durations between 1 and 12 hours in vacuo. The room temperature UV-Vis absorption spectra for all CuCl films showed both Z1, 2 and Z3 excitonic absorption features and the absorption intensity increased as the anneal time increased. Room temperature photoluminescence (PL) measurements of the hybrid films reveal very intense Z3 excitonic emission. Room temperature X-ray diffraction (XRD) confirmed the preferential growth of CuCl nanocrystals whose average size is ≈ 40 nm in the orientation. Resistivity measurements were carried out using a four-point probe system, which confirmed that the resistivity of the composite film was ≈500 Ω/cm. This is an improvement when compared to the vacuum evaporated CuCl thin films.
INTRODUCTION In nanostructures subjected to three-dimensional quantum confinement effects the optical properties can often be tailored by the confinement effect [1, 2]. CuCl has large exciton binding energy of the order of order 190 meV [3] and its exciton Bohr radius is very small (0.7 nm) [4]. CuCl nanocrystals belong to the weak-confinement regime because the CuCl nanocrystals’ typical average particle size larger than its Bohr radius [5]. At room temperature, γ-CuCl is an ionic I-VII compound semiconductor material with the zincblende structure [6]. It possesses two exciton absorption bands: one band is a doublet and the other is a singlet, historically called Z1, 2 and Z3, respectively, and separated by spin-orbit splitting appear in the near ultraviolet region [7]. The exciton binding energy of CuCl is considerably higher than those of semiconducting III-Nitrides and ZnO [8]. CuCl has been extensively used in the manufacture of electrooptic modulators and optical fibers [9], solid-state batteries [10], adsorbent and air purifying agents [11], catalysts [12], and as a candidate material for blue-UV light-emitting devices [13]. There are many physical and chemical procedures that have been demonstrated in preparing CuCl powders, nanocrystals and thin films, such as the reduction of copper (II) chloride (CuC
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