Effect of Fe-incorporation on photovoltaic characteristics of nano-structured CdSe thin films Abhijit A. Yadav ⇑ Thin Film Physics Laboratory, Department of Physics, Electronics and Photonics, Rajarshi Shahu Mahavidyalaya, Latur 413512, Maharashtra, India article info Article history: Received 24 August 2012 Received in revised form 17 October 2012 Accepted 20 October 2012 Available online 2 November 2012 Keywords: Thin films Chemical synthesis Electrochemical reactions Electrochemical impedance spectroscopy abstract The Fe-incorporated CdSe films are deposited on FTO-coated glass substrates by computerized spray pyrolysis technique. The Fe concentration is optimized by using photoelectrochemical (PEC) technique. The cell configurations CdSe/1 M (Na 2 S + S + NaOH)/C and Fe:CdSe/1 M (Na 2 S + S + NaOH)/C are used to study a wide range of photoelectrochemical characteristics including capacitance–voltage characteristics in dark, current–voltage characteristics in the dark and under illumination, photovoltaic power output and spectral response and to perform electrochemical impedance spectroscopy studies. The study reveals that the films exhibit n-type conductivity. Various parameters such as the junction ideality factor under illumination, series and shunt resistances, fill factor and efficiency are estimated for the PEC cell formed with CdSe and Fe-incorporated CdSe thin films. Band edges of Fe incorporated CdSe thin films are located. The best result obtained for conversion efficiency is 1.48% at 0.30 mol% Fe, which is three times more than the one reported for pure CdSe (0.50%) material. The value of fill factor is found to be improved from 0.44 to 0.63 with Fe incorporating in CdSe thin films. Electrochemical impedance spectroscopy studies show that incorporating of Fe into CdSe thin film improves the performance of resulting PEC cells. The utility of this work is in improving in efficiency of the PEC solar cell. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Semiconductor liquid junction solar cells have been attracting a great deal of attention for last few years due to growing interest in solar energy conversion. These cells are simple in construction and have the advantage that they can be used for both photovoltage and chemical energy conversion. In last decade, construction of photoelectrochemical cells with the aid of active semiconductor- electrolyte junction has been advanced as an alternative to well known method of energy conversion involving the use of solid state semiconductor solar cells [1–3]. The alternative method was searched because the usual solar cells are manufactured from highly pure and perfect crystalline materials and p–n junction is obtained using sophisticated technology. For this reason they are quite costly [4]. Semiconductor–electrolyte interface may be used for photoelectrolysis, photocatalysis and photoelectrochemical power generation [5–7]. The direct conversion of solar energy into electrical current using semiconductor-electrolyte interface was first demonstrated by Gerischer [8] and Eills et al. [9]. Since then a large number of metal as well as mixed chalcogenide and oxides have been used as photoelectrodes in PEC cells. The stability and efficiency of PEC cells are mainly dependent on preparation condi- tions for photoelectrode, electrolyte and experimental conditions set during experiment. The basic requirements of good thin film photoelectrode for PEC cells are low resistivity and larger grain size. Large grain size leads to reduction of grain boundary area of the thin film leading to an efficient energy conversion. The low resistivity of the photoelectrode is required to minimize the series resistance of the PEC cell which leads to lower the short circuit cur- rent [10,11]. Potentially, there are several advantages of PEC cells for solar energy conversion over conventional PV devices or Schottky bar- rier solar cells [12,13]: (1) PEC devices can store energy in the form of conventional fuel and can convert light to electrical energy as well; (2) PEC devices can be fabricated and modified with consid- erable ease. Contrary to PV devices, no solid–solid junctions are de- manded in PEC. The band bending characteristics of the semiconductor can be conveniently varied by suitable choice of electrolyte and cell variables; and (3) PEC cells do not have prob- lems associated with different thermal expansions of solid–solid junction. Binary II–VI group polycrystalline semiconducting materials have come under increased scrutiny because of their wide use in the cost reduction of devices for photovoltaic applications. Among the group, CdSe is an important material for the development of various modern technologies such as solar cells, high efficiency thin film transistors and light emitting diodes. A direct bandgap in the range of 1.65–1.84 eV has been reported for CdSe [14]. Undoped and doped cadmium chalcogenide thin films have been 0925-8388/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jallcom.2012.10.127 ⇑ Tel.: +91 9975213852; fax: +91 2382253645. E-mail address: aay_physics@yahoo.co.in Journal of Alloys and Compounds 552 (2013) 318–323 Contents lists available at SciVerse ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom