Thiocyanate functionalized ionic liquid electrolyte for photoelectrochemical study of cadmium selenide pebbles Sachin A. Pawar a , Dipali S. Patil a , Sandip K. Patil b , Deepak V. Awale b , Rupesh S. Devan c , Yuan-Ron Ma c , Sanjay S. Kolekar b, *, Jin-Hyeok Kim d, **, Pramod S. Patil a, * a Thin Film Materials Laboratory, Department of Physics, Shivaji University, Kolhapur 416 004, India b Analytical Chemistry and Materials Science Research Laboratory, Department of Chemistry, Shivaji University, Kolhapur 416 004, India c Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan d Department of Materials Science and Engineering, Chonnam National University, Gwangju 500 757, South Korea A R T I C L E I N F O Article history: Received 10 July 2014 Received in revised form 20 September 2014 Accepted 11 October 2014 Available online 18 October 2014 Keywords: Ionic liquid electrolyte CdSe solar cell XPS A B S T R A C T A thiocyanate functionalized ionic liquid based electrolyte is developed for the application in CdSe thin ﬁlm solar cell. An aqueous solvent consisting of polysulﬁde and thiocyanate functionalized IL has been found as the optimum solvent for preparing the liquid electrolytes. This solvent ratio appears to give higher cell efﬁciency compared to pure aqueous polysulﬁde electrolyte. Polysulﬁde and thiocyanate functionalized IL give rise to a good redox couple in the electrolyte for photoelectrochemical performance. The CdSe photoanode used for solar cell study has been synthesized by a simple and cost-effective one-step, one-pot chemical bath deposition method onto the F: SnO 2 substrates. The as-deposited ﬁlms were annealed at temperatures 100, 200, 300 and 400  C, respectively for 1 h in ambient air. The maximum current density of 3.55 mA/cm 2 for the sample annealed at 300  C is observed in the polysulﬁde electrolyte with the power conversion efﬁciency 0.76%. Addition of thiocyanate functionalized IL in polysulﬁde produced the highest current density of 4.93 mA/cm 2 with the two fold increase in the power conversion efﬁciency up to 1.32%. ã 2014 Elsevier Ltd. All rights reserved. 1. Introduction Electrolyte is an important factor as like the electrode material for the efﬁcient solar cell. As per the green context, Ionic Liquids (ILs) successfully replaces the conventional organic solvents in photoelectrochemical solar cells. Due to the unique physico- chemical properties they can be employed as an electrolyte in electrochemical systems. IL electrolytes have great affect on energy conversion efﬁciency and stability of solar cells. Graetzel proposed IL based dye sensitized solar cells (DSSCs) which are potentially the ideal basis of a liquid or gel electrolyte. It is now possible to depart completely from the classical solid-state junction device, by replacing the contacting phase to the semiconductor by an electrolyte, liquid, gel or solid, thereby forming a photoelectro- chemical cell. The phenomenal progress realized recently in the fabrication and characterization of nanocrystalline materials has opened up vast new opportunities for these systems [1]. ILs are room temperature molten salts that entirely consist of ions and are liquid at or close to room temperature. ILs can exhibit advantageous properties like high thermal and chemical stability, negligible volatility, ﬂame retardancy, moderate viscosity, high polarity, low melting point, high ionic conductivity, solubility (afﬁnity) with many compounds [2,3]. Their physical and chemical properties can be tailored by tuning the pairing and structure of the cations and anions, so that they are also known as “designer solvents”. Many ILs offer a range of properties that make them attractive to the ﬁeld of electrochemistry. A variety of electro- chemical devices including solar cells, high energy density batteries, fuel cells and supercapacitors have become of intense interest as part of various proposed solutions to improve sustainability of energy supply in our societies [4]. Thus, they pertain to a new class of electrolytes that, in contrast to ordinary electrolytes, contain no molecular solvent. The keen attention to IL was due to their properties such as the wide liquid state interval, incombustibility and explosion safety, non-volatility (very low vapor pressure); certain ILs are characterized by relatively high ion * Corresponding author. Tel.: +91 231 2609490; fax: +91 231 2691533. ** Corresponding author. E-mail addresses: sskolekar@gmail.com (S.S. Kolekar), jinhyeok@chonnam.ac.kr (J.-H. Kim), patilps_2000@yahoo.com (P.S. Patil). http://dx.doi.org/10.1016/j.electacta.2014.10.047 0013-4686/ ã 2014 Elsevier Ltd. All rights reserved. Electrochimica Acta 148 (2014) 310–316 Contents lists available at ScienceDirect Electrochimica Acta journal homepa ge: www.elsev ier.com/locate/electacta