Contents lists available at ScienceDirect Thin Solid Films journal homepage: www.elsevier.com/locate/tsf Fabrication of conducting polymer modified CdS photoanodes for photoelectrochemical cell Alka Pareek a,b , Pradip Paik b,1 , Joydip Joardar a , K. Murugan a , Pramod H. Borse a, ⁎ a International Advanced Research Centre for Powder Metallurgy and New Materials, Balapur PO, Hyderabad, Telangana 500 005, India b School of Engineering Science and Technology, Hyderabad Central University, Gachibowli, Hyderabad 500046, Telangana, India ARTICLE INFO Keywords: Photoelectrochemical cells Hydrogen generation Spray deposition Cadmium sulfide Electrochemical polymerization Polypyrrole Polyaniline ABSTRACT The present work focuses on the modification of a spray deposited nanostructured CdS thin films by thin layers of polyaniline (PANI) and polypyrrole (PPY) systems using electro-polymerization method. The deposition of the conducting polymer on the CdS/FTO (Fluorine doped tin oxide) film surface has been validated by X-ray dif- fraction, UV–Vis spectrometry and Fourier transform infrared spectrometry. As deposited PANI and PPY films exhibit a bandgap of 2.0 eV and 1.7 eV, respectively. Optimization of deposition parameters viz. applied field, concentration of monomer and pH of the precursor has been performed to obtain a uniform and an adherent coating over CdS surface. The absorption band-edge of CdS is not shifted due to its surface modification via. PANI and PPY. However coating of PANI enhanced the visible light absorption capacity of CdS. This additionally ensures that there exists a thin polymer coating over CdS. The photocurrent of CdS/PANI and CdS/PPY is found to be enhanced by 3.2 and 2.6 times as compared to the bare CdS. An improvement in the PEC performance could be attributed to the favorable band energetics between the conjugated polymers and CdS that effectively reduces the recombination process and thus enhances the charge transfer process. 1. Introduction Photoelectrochemical (PEC) cell is a reliable technology to handle the ever-growing and huge energy demand for present and future era [1]. This engraving technology has triggered a surge of development in the solar active semiconducting nanostructures those suit as photo- anode for their solar applications [2]. Among them CdS is one of the most studied materials due to its narrow bandgap (2.4 eV) and desirable band-edge positions for the cleavage of water molecule [3, 4]. Still it lacks the recognition of a potential candidate, as it has low charge- separation efficiency and has stability issues but not as severe as Ga- Arsenide systems. There are number of reports focussing on the im- provement of CdS efficiency by means of various [5] methods viz. loading of noble metals (Pt, Au, Ag etc.) on the surface of CdS [6], doping of CdS lattice and formation heterojunction of CdS with other semiconductors [7] and/or conjugated polymers [8]. Conjugated or conducting polymers like polypyrrole (PPY), poly- aniline (PANI) and polythiophene has attracted a lot of attention re- cently owing to their excellent electrical, optical and magnetic prop- erties [9]. These polymers are used as photosensitizer to enhance the absorption of the semiconductor to visible range [10], form an outer layer on the surface of semiconductor to inhibit its photocorrosion [11] and further even improve the charge-transfer process at the hetero- junction [12]. The conducting polymers exhibit valence bandedge po- sition more negative than the semiconductor, which mediates an effi- cient hole transfer at the interface [13, 14]. This process reduces electron-hole recombination at the interface and facilitates an increase in the photocurrent. Among all the conducting polymers, polypyrrole (i.e. –C 4 H 4 NH– n ) and polyaniline are mostly studied due to important factors as:- (1) the oxidative polymerization potentials of the pyrrole and aniline are lower than other conducting polymers; (2) the electro- polymerization of pyrrole and aniline can be performed in acidic aqu- eous solutions, while other conducting polymers requires non-aqueous solution; (3) the electrical conductivity of as deposited polymer is higher for PPY and PANI; and (4) PPY and PANI are eco-friendly con- ducting polymers [15]. There are various reports on the PPY/inorganic and PANI/inorganic semiconductors due to their high conductivity, environmental stability and their ease of synthesis [16]. Lu et al. discussed the photo- luminescence properties of the nanocomposite films of PPY having https://doi.org/10.1016/j.tsf.2018.07.020 Received 21 July 2017; Received in revised form 10 July 2018; Accepted 14 July 2018 ⁎ Corresponding author. 1 Present address (lien from University of Hyderabad): Dr. Pradip Paik, Associate Professor, School of Biomedical Engineering, Indian Institute of Technology (IIT)- BHU, Varanasi, UP, PIN 221005. E-mail address: phborse@arci.res.in (P.H. Borse). Thin Solid Films 661 (2018) 84–91 Available online 17 July 2018 0040-6090/ © 2018 Published by Elsevier B.V. T