Effect of zinc chloride on structural, optical and dielectric behavior of solution grown anthracene crystal Nidhi Sinha b , Manoj K. Gupta a , Neeti Goel a , Binay Kumar a,n a Crystal Lab, Department of Physics and Astrophysics, University of Delhi, Delhi 7, India b Department of Electronics, SGTB Khalsa College, University of Delhi, Delhi 7, India article info Article history: Received 2 March 2011 Received in revised form 28 March 2011 Accepted 18 April 2011 Available online 19 May 2011 Keywords: Organic semiconductor Crystal growth XRD Phase transition Dielectric PL abstract Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation method. In XRD studies a shift in peaks towards higher theta value and change in preferred orientation from (0 0 1) to (0 0 2) were observed as a result of doping. UV–vis spectra show a blueshift of various peaks in ANZ. Remarkable increases in dielectric constant and AC conductivity were observed along with a structure related phase transition at 40 1C in ANZ at atmospheric pressure itself. Good fluorescence properties with a strong green emission were observed in photoluminescence studies. & 2011 Elsevier B.V. All rights reserved. 1. Introduction Organic materials are of great interest for electronic applica- tions, as they have many advantages over their inorganic counter- parts. There has been a recent surge for identification of new high quality single crystals of organic semiconductors for various electronic devices, notably organic thin film transistors (OTFT) [1,2]. Significant developments in the field of organic semicon- ductors have been conspicuous, such as light-emitting diodes, field-effect transistors, solar cells, and so forth [3–5]. Among important organic semiconducting aromatic molecules, anthra- cene (C 14 H 10 ) is a model molecule for conjugated organic semi- conductors since many decades [6]. Anthracene is commonly treated as the archetype of molecular crystals, which has many advantages like light weight, low price, high flexibility, non- polluting and easy to fabricate in large scale optical devices [2,6]. In anthracene crystal, the doping is an efficacious way to improve the performance of organic semiconductor devices [7]. The nature and concentration of defects induced by doping are very important features of molecular crystals, as they usually strongly influence the electrical and optical properties, which are promising in low-cost applications of these crystals as photo- conductors and scintillators [7,8]. Furthermore, a phase transition in pure anthracene under high pressure and analogous behavior related to structural and electronic properties has been reported [9]. Herein, we present an observation of phase transi- tion in anthracene crystal as a consequence of ZnCl 2 doping at atmospheric pressure. The AN and ANZ crystals were character- ized by various techniques such as X-ray diffraction, FT-IR, PL, UV–vis, Dielectric, AC conductivity, etc. 2. Experimental details Pure and zinc chloride doped anthracene crystals (named AN and ANZ, respectively), were grown by the slow evaporation technique. A saturated solution of anthracene was prepared in acetone after checking its solubility. The starting material was synthesized by taking anthracene powder and acetone (solvent). Similarly, anthracene and zinc chloride were taken in 1:1 molar ratio and dissolved in acetone according to solubility and the whole solution was stirred for 2 h using a magnetic stirrer to obtain a homogeneous solution. The solution was filtered to remove the suspended impurities and then the solution was allowed to crystallize by slow evaporation of solvent at 30 1C for about 10 days. Well-defined single crystals of AN and ANZ with good transparency were collected. The XRD patterns were taken at room temperature using a Bruker X-ray diffractometer with CuKa 1 radiation (1.5405 ˚ A). FT-IR spectra were recorded using a Perkin Elmer Spectrum BX in the range of 400–4000 cm 1 at 4 cm 1 resolutions using KBr pellets. The dielectric constant was measured using an Agilent E4980A LCR meter in the frequency Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/physb Physica B 0921-4526/$ - see front matter & 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2011.04.073 n Corresponding author. Tel.: þ91 9818168001; fax: þ91 011 27667061. E-mail address: b3kumar69@yahoo.co.in (B. Kumar). Physica B 406 (2011) 3206–3209