International Journal of Science and Research (IJSR) ISSN: 2319-7064 ResearchGate Impact Factor (2018): 0.28 | SJIF (2018): 7.426 Volume 8 Issue 5, May 2019 www.ijsr.net Licensed Under Creative Commons Attribution CC BY Characterization of Pb Doped CdS Thin Film Fabricated by Spray Pyrolysis Deposition Technique Mousumi Kundu 1 , Mst. Halima Khatun 2 , Sajal Khan 3 , Md. Shahjahan 4 Bangabandhu Sheikh MujiburRahman Science & Technology University, Department of Applied Physics Electronics and Communication Engineering, Bangladesh Abstract: Undoped and Pb-doped CdS (Pb:CdS) thin films were prepared by a spray pyrolysis technique on glass substrates at 300 0 C substrate temperature for different doping concentrations. The physical properties of the films were studied as a function of increasing lead dopant concentration. Structural, optical and electrical properties of these films have studied for photovoltaic applications. The structural and optical properties of the prepared films were characterized using XRD and UV-VIS spectroscopy. X-ray diffraction (XRD) patterns revealed that the samples have hexagonal crystal structure. The particle size of the crystallites was found to be in the range 20- 62 nm for CdS film. The optical properties of the Pb:CdSthin films have been studied at room temperature in wavelength range 400 nm to 1100 nm.The variation of energy band gap for the films with different doping concentrations was studied. The resistivity decreases with increase of the temperature which confirms semiconductor behavior and it depends on the doping concentrations.Hall measurements were done in air ambient at room temperatureand the samples are found n-type semiconductor. Keywords: Spray pyrolysis, Dopant, Band gap, CdS 1. Introduction Thin films of polycrystalline semiconductors has extremely wide range of physical and chemical properties makes them important material both for technological and industrial applications. Cadmium sulfide (CdS) belongs to II - VI compound semiconductor which has a wide direct band gap of E g .=2.36−2.45 eV at room temperature. CdS is currently used as a window layer in thin film solar cells[1], because of its large band gap and high transparency [2].The deposition of CdS films has been explored by different techniques: sputtering, thermal evaporation, chemical bath deposition, and molecular beam epitaxy[3,4]. Spray pyrolysis deposition (SPD) technique provides a simple route of synthesizing thin films because of its simplicity, low cost experimental set up from an economic point of view[5,6]. Lead doped cadmium sulfide (Cd 1-x Pb x S) films are getting attention in recent years due to their promising applications in fabricating blue and green light emitting diodes[7], laser diodes, waveguide[8], logic gate and field emitter, photoconductor[9],nano-rods and thin films in energy conversion. This work presents the influence of Pb doping on the structure of CdS thin films, by using the spray pyrolysis technique. The effect of Pb incorporation in CdS on the structural, optical and electrical properties has been investigated to determine the feasibility of CdS films for the potential technological applications. 2. Experimental Details The working solution was prepared by taking cadmium chloride [CdCl 2 .H 2 O], Lead acetate [Pb (CH 3 COO) 2 .2H 2 O] and NH 2 CSNH 2 as a source material and distilled water was used as solvent. All the precursor solution was prepared in the molar concentration of 0.1 M for spraying. The Pb doping concentrations were varied from 1% and 2% (% wt.). The prepared solutions were maintained under continuous magnetic stirring at room temperature for one hour. Before spraying on the glass substrates were first cleaned with liquid detergent, dipped into chromic acid mixture and then cleaned thoroughly in a stream of cold water. The temperature of the substrate was controlled by controlling the heater power by using a variac. The substrate temperature was measured by placing a copper constant thermocouple on the substrate. The substrate temperature was adjusted at 300ºC for film deposition.After deposition the films were annealed at 450ºC for an hour. The crystalline structure of the films were determined XRD (Bruker D2) CuKα radiation of wavelength λ= 1.54185 Å for 2θ values over 20°- 70°. Peak positions were identified with JCPDS card No.41e1049.The optical transmission and absorption spectra of the CdS:Pb thin films have been studied at room temperature in wavelength range 400nm to 1100nm usingUV–Vis spectrophotometer. Resistivity of the films has been measured within the temperature range 305 K to 465 K using Van der Pauw configuration and Hall measurement system reveals the type of the semiconductor. 3. Results and Discussion 3.1 Structural properties The XRD pattern of undoped and doped CdS thin films shown in Fig.1gives the information of different crystallographic phases and preferred orientations. The films have remarkable peaks and so, it can be concluded that the films are crystalline in nature in all the cases. The corresponding (hkl) values of (100), (002), (101), (102), (110), (103) and (112) planes confirms the hexagonal crystal structure of pure CdS (JCPDS card No.41e1049). It has been reported in the literature that the probability that CdS Paper ID: ART20197311 10.21275/ART20197311 307