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262 presentation1

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262 presentation1

  1. 1. Crystalline Zinc Indium Selenide thin film electrosynthesis and its photoelectrochemical studies By Anuradha Bhalerao-Pawar, B.G. Wagh, N.M. Shinde, S. B. Jambure, C.D.Lokhande K.K.Wagh Institute of Engineering Education & Research, Nasik K.K.Wagh Arts, Commerce & Science College, Pimpalgaon Nasik. Department of Physics, Shivaji University, Kolhapur.
  2. 2. Outline 1. a. Thin Film Science and b. Thin Film Deposition Techniques 2. Electrodeposition of Zinc Indium Selenide Thin films 3. Structural Analysis of Thin Film 4. PEC Study of Thin Film
  3. 3. 1a. Thin Film Science Third Dimension Negligibly Smaller Two Dimensional Solids Thickness less than 100nm Thin Film
  4. 4. Effect of Film Thickness on Material Properties When Thickness is comparable with Mean Free Path of Electrons Resistivity & Dielectric constants Vary as a function of thickness Rigidity & Transparency Alters with thickness
  5. 5. 1b. Thin Film Deposition Techniques Physical Deposition : One of the Physical Properties is Altered Chemical Deposition: Use of Chemical Reaction Biological Deposition : Use of Biological Reaction Hybrid Deposition: Mixing of Above Techniques Electrochemical Deposition
  6. 6. Experimental Set-Up • Experimental set up consists of : 1. Anode Counter Electrode (C) 2. Cathode Working Electrode (W) 3. A Suitable Electrolyte. • When electric current passed through electrolyte: Ionic movement starts
  7. 7. Experimental Mechanism W - +++ --- - +- ++ ---+ C + + + + + + Charge Transfer across Electrode and Electrolyte causes Charge Cloud formation near the Electrodes Positive ions deposit on cathode forming a thin film. The amount of material electroplated depends upon: The direction of current existing at particular region of electrode. The uniform current distribution : A uniform film.
  8. 8. 2. Electrodeposition of Zinc Indium Selenide Thin Films
  9. 9. Experimental Details Working Electrode Stainless Steel Plate with Surface Treatments Counter Electrode Reference Electrode Graphite Rod Standard Calomel Electrode (SCE) Electrolyte: ZnSo4 (0.2M), InCl3 (0.02M) and SeO2 0.002M) Temperature : Ambient pH : 2.2 Potential : -600mV
  10. 10. Potential Optimization Potential Vs SCE (mV) 0 200 400 600 800 1000 c 2 Current Density (mA/cm ) 0 a 1 2 b d 3 4 ZnSO4 InCl3 SeO2 ZnSO4+InCl3+SeO2 5 The polarization curves for reduction of (a) zinc, (b) indium, (c) selenium and (d) for the bath containing precursor solutions
  11. 11. 3.Structural Analysis Intensity (A.U.) (Substrate ) (400) 800 (116) (112) 1000 (301) (220) ZnIn2se4 Data JCPDS File No. 39-1156 600 400 200 10 20 30 40 50 60 70 80 Degree) The X-ray diffraction pattern of as-deposited ZnIn2Se4 thin film shows Tetragonal crystal structure with remarkable growth along (220) plane
  12. 12. Surface Morphology The scanning electron micrographs of ZnIn2Se4 film electrode at magnification 10,000 over growth observed And at 30,000 magnification : Well resolved uniform grain growth observed. Local edge sharing rod like structure observed with breadth in nanorange (500nm )
  13. 13. Optical Absorbance Study 60000 % Absorbance x 10-11(eV/cm)2 Absorbance 300 400 500 600 700 800 W avelength (  ) (nm )  h   30000 0 1.6 2.0 2.4 2.8 3.2 3.6 4.0 4.4 h(eV) Inset shows : Material shows good absorbance in wavelength region 400-500nm Energy band gap of the material : 2.4eV Blue Shift of 0.1eV
  14. 14. 4.Photo Electrochemical [PEC] Study of Thin Film PEC Cell Solid – Electrolyte Junction Electrochemical Photovoltaic Cell (ECPV Cell) Free Energy Change = 0 Photo Electrode (Thin Film) Photoelectrosynthetic Cell Free Energy Change Non Zero Electrolyte Counter Electrode
  15. 15. Use of Zinc Indium Selenide Thin Film as Photo Electrode in S-E Junction Space Charge + + + + Bulk + + Semiconductor + + Ionized Group - - - Helmholtz Double Layer Electrolyte Solid- Electrolyte Junction Barrier is Formed due to Transfer of Majority Carriers from Semiconductor to Electrolyte Major Potential Drop in Semiconductor Space Charge Layer. Only small fraction of Drop in Electrolyte Region
  16. 16. ECPV Cell : Action at Photo electrode Photo electrode Exposed Electron-Hole Pairs Generated in Depletion Region E-H Pair Driven Apart by Electric Field at Interface (Photo voltage) Holes react with Electrolyte and Redox completes at CE Electrons move from Photo anode to Counter Electrode
  17. 17. Chopping 2 Current Density ( A/cm ) Photoelectrochemical Cell output parameter 100 0 -600 -400 -200 0 -100 Dark Current Light Current 2 Dark Current Light Current Current Density (A/cm ) 200 250 Dark 200 Light 400 600 Voltage (mV) 0 Dark -250 Light -500 -750 -1000 -200 -750 -500 -250 0 250 500 Voltage (mV) The Current–voltage (I–V) characteristic in dark and under light illumination (a) photovoltaic power output characteristics : Isc=0.05mA/cm2 Voc=250mV (b) light chopping : n-Type conductivity (magnitude of voltage increases with negative polarity towards Zinc Indium Selenide electrode
  18. 18. Speed of response and Transient photoresponse characteristics 20 Voltage Light Dark Chopping -270 Voltage (mV) Current (A) 15 10 -275 -280 -285 5 20 40 Time (S) 60 20 40 60 Time(S) Speed of Response Photo induced voltage as a function of time
  19. 19. Capacitance–voltage (C–V) characteristics Mott–Schottky plot of PEC cell.
  20. 20. Electrochemical Impedance Spectroscopic (EIS) Study Raw data Fitted data 3500 3000 -Z'' (Ohm) 2500 2000 1500 1000 500 0 -500 0 2000 4000 6000 8000 10000 Z' (Ohm) Nyquist plot for ZnIn2Se4 electrode Equivalent circuit derived from Nyquist plot
  21. 21. Component values of equivalent circuit Parameter (1) Rs (2) R1 (3) C1 (4) R2 (5) Qy2 (6) Qa2 Value Error 49 Ω 6.4 1019.19Ω 10743.32 0.002484 F 0.047381 8431.614Ω 11644.95 6.74E-05F 2.54E-05 0.838F 0.0764
  22. 22. Conclusion 1. X-ray Diffraction Analysis: Tetragonal Crystal Structure 2.SEM Analysis : Homogeneous local edge sharing network structure 3.Optical Absorbance study : Direct band gap semiconducting material 4. Photovoltaic Power output characteristics: Photosensitive material Used as Buffer layer in photovoltaic device 5.Speed of Response and Transient Photo response : Use of this material as light sensor Stability of electrode 7.Mott-Schottky plot : Flat Band Potential : -0.8 V/SCE
  23. 23. Acknowledgement 1.Contribution of Pune University Research Fund under BCUD scheme 2. Motivation of K.K.Wagh Institute of Engineering Education and Research, Nasik
  24. 24. Thanks 1. ICAER Co-ordination Committee 2. Energy Angels

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