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Sin Khai Wen FYP Viva Presentation

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Khai Wen Sin

This document summarizes a final year project on depositing CdSe nanoparticles multilayers using chemical bath deposition. It introduces CdSe and its properties, the chemical bath deposition technique, and how it was used to deposit different sized CdSe nanoparticles by varying the concentration of the complexing agent NTA. Characterization of the deposited nanoparticles found smaller sizes were produced with higher NTA concentrations. Attempts to deposit two CdSe layers of different sizes on a substrate did not improve solar cell efficiency compared to a single layer. Further work is recommended to address Ostwald ripening in the deposition solution.

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We l e a d Final Year Project 2015/2016 Final Year Project Title: Deposition and Characterization of CdSe Nanoparticles Multilayer on Conductive Substrate by Chemical Bath Deposition Final Year Project Viva Presentation Name: Sin Khai Wen No. Matric: 116541 Supervisor: Dr. Khatijah Aisha Bt. Yaacob
We l e a d Introduction of CdSe • Important II-VI compound because of its size-dependent exceptional optoelectronic properties in the visible range • It has a direct bulk band gap (1.74 eV) with high absorption coefficient near the band edge, high photosensitivity, tunable band gap from around 450 to 700nm which cover the entire visible spectral range and quantum size effect, allow its use in thin film devices, especially for application in solar hybrid system. • Solar cell, light emitting diode, nano sensors, photo detectors Figure 1: Left, absorption spectra of differently sized CdSe nanocrystals. Right, corresponding PL spectra representing deeper red, red, orange, yellow, green and blue (from right to left) emitting CdSe cluster and nanocrystals under UV excitation at 380nm (Yuan & Krüger, 2012) Yuan, Y. & Krüger, M., 2012. Polymer-Nanocrystal Hybrid Materials for Light Conversion Applications. Polymers, Volume 4, pp. 1-19.
We l e a d Introduction of Chemical Bath Deposition • Chemical bath deposition (CBD) is the simplest deposition technique that do not require sophisticated and costly instruments. • Extensively used for preparation of CdSe thin film because of its application as window layer material in solar cell fabrication • Chemical Reaction: Cadmium salt reacted with NTA to form complex Cd salt, Cd2+ + NTA [Cd(NTA)]2+ (1) Hydrolysis of potassium hydroxide in water gives OH- ions in solution according to the equation, KOH(s) + H2O(l) K+ (aq) + OH- (aq) + H2O (l) (2) Hence, from reaction of (1) and (2), it will give solid Cd(OH)2 formation. Cd2+ + 2OH-  Cd(OH)2 (s) (3) From the reaction of selenium and sodium sulfite, we will get equation (4), and when dissolving in [Cd(NTA)]2+ solution, the byproduct is (5) Na2SO3 + Se Na2SeSO3 (4) SeSO3 2- + OH- HSe- + SO4 2- (5) The overall reaction can be described as follow Cd(OH)2 (s) + HSe- CdSe + OH- + H2O (6) ,
We l e a d Introduction of QDSSC Figure 2: Operating principle of a typical QDSSC (Jun, et al., 2013) • The electrons will enter into the conduction band (CB) of the QD and the hole remains in the valence band (VB). • The excited QD injects the electron from its CB into the CB of the wide band gap semiconductor (e.g. TiO2) and become oxidised. • The injected electron from the QD percolates through the porous TiO2 , reaches the conducting glass, travels through the external load, completes the circuit. • The oxidized QD is then restored (hole is filled with electron) when it is reduced by S2- from the electrolyte and in turn it is oxidized into S2- that diffuses to the counter electrode. Jun, H., Careem, M. & Arof, A., 2013. Quantum dot-sensitized solar cells-perspective and recent developments: A review of Cd chalcogenide quantum dots as sensitizers. Renewable and Sustainable Energy Reviews, Volume 22, pp. 148-167.
We l e a d Problem Statement • The deposition process in CBD uses a controlled chemical reaction which result in the deposition of a nanocrystalline films by precipitation • Small crystal size leads to quantum size effect and increase in the optical band gap • The major problem of the CBD method is the difficulty to produce small CdSe nanoparticle on the substrate • Another problem is deposition of CdSe multilayer with different size of CdSe nanoparticles on the substrate
We l e a d Research Objectives • To synthesis different CdSe nanoparticle size using chemical bath deposition method by changing parameters such as complex agent concentration. • To deposit two layer of CdSe nanoparticles with different particle size on fluorine doped tin oxide(FTO) substrate. • To determine and compare electrical properties of CdSe multilayer with CdSe single layer solar cell.
We l e a d Methodology- Procedure FTO cleaning – 2-propanol Deposition of TiO2 mesoporous layer Deposition of CdSe on the mesoporous TiO2 thin films by using chemical bath deposition method Parameters: • NTA concentration • Deposition time • Deposition of multilayer CdSe thin film Characterization: • XRD • SEM • UV-Vis • EDX Synthesis of polysulfide electrolyteFabrication of Cu2S photocathode Solar cell assembly Characterization • Photo-electrochemical Measurement (I-V)
We l e a d Methodology Figure 3: Polysulfide electrolyte Figure 4: Brass counter electrode after immersed in 37% HCl at 70°C for 45 minutes Figure 5: Cell assembly with polysulfide electrolyte injected between the two electrodes
We l e a d Result and Discussion (a) (b) Figure 6: TiO2 thin films (a) before annealed and (b) after annealed TiO2 nanoparticle Pore Structure Figure 7: FESEM image of TiO2 mesoporous layer at magnification 30.00KX TiO2 Mesoporous Layer
We l e a d Result and Discussion 0 0.5 1 1.5 2 2.5 340 390 440 Absorbance(a.u) Wavelength(nm) 0 5 10 15 20 25 30 35 40 3.2 3.3 3.4 3.5 3.6 (hv)2 optical band gap(eV) Figure 8: Absorbance spectra of TiO2 mesoporous layer Figure 9: (αhν)2 versus optical band gap
We l e a d Result and Discussion Figure 10: CdSe solution with 240, 180 and 120mM NTA from left to right 240mM NTA 180mM NTA 120mM NTA CdSe Solution
We l e a d Result and Discussion XRD Analysis of CdSe Nanoparticles Figure 11: XRD pattern of CdSe at different NTA concentration selenium oxide Figure 12: XRD pattern of CdSe quantum dots (Mahajan, et al., 2013) S.Mahajan, Rani, M., Dubey, R. B. & Mahajan, J., 2013. Characteristics and Properties of CdSe Quantum Dots. International Journal of Latest Research in Science and Technology, 2(1), pp. 457-459.
We l e a d Sample Matching peaks (hkl) 2θ (degree) Spacing, d (Å) FWHM, β (°) Crystallite size (nm) 120mM NTA CdSe 111 24.27 3.66 0.620 13.00 180mM NTA CdSe 111 25.87 3.44 0.889 8.56 240 mM NTA CdSe 111 25.44 3.50 3.16 2.45 Table 1: Different parameters of different NTA concentration of CdSe nanoparticles obtained from XRD Result and Discussion Scherrer’s Equation to calculate crystallite size, D = 0.94λ β cosθ
We l e a d Result and Discussion FTIR Analysis of CdSe Nanoparticles Figure 13: FTIR spectra of CdSe at different NTA concentration H bond (-OH group) C-H bondingCOO- stretchingC-O group, NTA exist Cd(OH)2 Zhang, A. et al., 2012. Suppressed blinking behavior of CdSe/CdS QDs by polymer coating. Nanoscale, pp. 1-8. Ingole, P. P. & Haram, S. K., 2010. Citrate-capped Quantum dots of CdSe for the Selective Photometric Detection of Silver Ions in Aqueous Solutions. Liu, I.-S.et al., 2008. Enhancing photoluminescence quenching and photoelectric properties of CdSe quantum dots with hole accepting ligands. Journal of Materials Chemistry, Volume 18, pp. 675-682. Corer, S. & Hodes, G., 1994. Quantum Size Effects in the Study of Chemical Solution Deposition Mechanisms of Semiconductor Films. J. Phys. Chem, Volume 98, pp. 5338-5346. To determine the existing of Cd(OH)2 because hydroxide crystal from Cd(OH)2 in solution, act as nuclei for formation of CdSe (Corer & Hodes, 1994).
We l e a d Result and Discussion UV-Vis of CdSe nanoparticles with different concentration of NTA 0.4 0.6 0.8 1 1.2 400 500 600 700 Absorbance Wavelength(nm) 120mM NTA CdSe 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 400 500 600 700 Absorbance Wavelength(nm) 180mM NTA CdSe 0.4 0.6 0.8 1 1.2 400 500 600 700 Absorbance Wavelength(nm) 240mM NTA CdSe Figure 14: a) Absorption spectra of CdSe at NTA concentration of 120mM, b) Absorption spectra of CdSe at NTA concentration of 180mM, c) Absorption spectra of CdSe at NTA concentration of 240mM (a) (b) (c)
We l e a d Average diameter, D= (1.6122x10-9)λ4-(2.6575x10-6) λ3+(1.6242x10-3) λ2-(0.4277) λ+41.57 (Peng, et al., 2003) Sample 120mM NTA CdSe 180mM NTA CdSe 240mM NTA CdSe Wavelength (nm) 608.94 554.98 587.48 Average Diameter (nm) 5.00 3.14 4.09 Band gap energy (eV) 1.93 2.10 1.95 Result and Discussion Table 2: Wavelength, average diameter and band gap energy of CdSe at different concentration Yu, W. W., Qu, L., Guo, W. & Peng, X., 2003. Experimental Determination of the Extinction Coefficient of CdTe, CdSe, and CdS Nanocrystals. Chemistry Material, Volume 15, pp. 2854-2860.
We l e a d Result and Discussion 120mM NTA 180mM NTA 240mM NTA 8 hr 14 hr 20 hr 26 hr Figure 15: Deposited CdSe for 26 hours on FTO glass with different NTA concentration Figure 16: Deposited CdSe with NTA concentration of 240mM at different time Deposition of CdSe on TiO2 Mesoporous Layer
We l e a d Result and Discussion Time deposition (hr) 10.0KX 30.0KX 8 14 20 26 Figure 17: FESEM image of CdSe from concentration of 180mM at different time under magnification of 10.0KX and 30.0KX
We l e a d Result and Discussion NTA concentration (mM) Time deposition (hr) Short Circuit Current Density, Jsc (mA/cm2) Open Circuit Voltage, VOC (V) Fill factor, FF Efficiency, η (%) (x 10-2) 8 0.055 0.145 0.323 2.6 120 14 0.095 0.085 0.366 3.0 20 0.465 0.091 0.283 12.0 26 0.905 0.182 0.286 47.1 8 0.212 0.184 0.388 15.1 180 14 0.350 0.217 0.281 21.3 20 0.127 0.160 0.336 6.8 26 0.105 0.123 0.283 3.7 8 0.967 0.227 0.316 69.4 14 0.509 0.195 0.326 32.4 240 20 0.550 0.131 0.244 17.6 26 0.448 0.131 0.331 19.4 Table 3: Summary of short circuit current density, open circuit voltage and efficiency at 120mM,180mM and 240mM NTA concentration
We l e a d Result and Discussion Deposition of CdSe Nanoparticles Multilayer on TiO2 Mesoporous Layer Figure 18: CdSe multilayer deposited with 1st layer is from 120mM NTA concentration at 26 hours and 2nd layer is from 180mM NTA concentration at 14 hours CdSe multilayer FTO glass fracture Figure 19: FESEM image of cross section image of CdSe multilayer on FTO glass at magnification of 1KX
We l e a d First Layer Second Layer Short Circuit Current Density, Jsc (mA/cm2) Open Circuit Voltage, VOC (V) Fill factor, FF Efficiency, η (%) (x 10-2) NTA concentration (mM) Time deposition (hr) NTA concentration (mM) Time deposition (hr) 120 (b) 26 180 14 0.521 0.176 0.310 28.4 120 (b) 26 240 8 0.132 0.070 0.297 2.7 180 14 120 (b) 26 0.102 0.027 0.310 0.9 180 14 240 (b) 8 0.303 0.080 0.195 4.7 240 8 120 (b) 26 0.722 0.251 0.271 49.1 240 (b) 8 180 14 0.302 0.155 0.262 12.3 Result and Discussion Table 4: Summary of short circuit current density, open circuit voltage and efficiency for deposited CdSe multilayer at different NTA concentration and different time deposition * (b) means bigger average diameter of particles
We l e a d Conclusion • By changing NTA complex agent concentration with 120mM, 180mM and 240mM, different CdSe nanoparticle size 5.00nm, 3.14nm and 4.09nm with band gap energy 1.93eV, 2.10eV and 1.95eV had been synthesized respectively. • For NTA concentration of 120mM, as time deposition increased, the efficiency also increased. However, for NTA concentration of 180mM and 240mM, overall efficiency decreased as the time deposition increase. • Two layer of CdSe nanoparticles with different particle size had been deposited on FTO substrate by CBD method. • However, 2nd layer deposition of CdSe did not enhance the overall cell efficiency
We l e a d Recommendation • Ostwald ripening process in the CdSe solution gives low conversion efficiency of the cells. • The change in colour from yellow, orange and then finally red or dark red shown that CdSe nanoparticles growing bigger. • To avoid ostwald ripening, once the CdSe solution is synthesized, the substrate should be deposited at once so that the CdSe nanoparticles can be deposited onto substrate and nucleation takes place on the substrate before agglomeration occurs. • Higher temperature deposition can be carried out too so that the CdSe nanoparticles gain energy and will not agglomerate together. • Besides that, when the CdSe solution is not used, the solution should always be stirred so that the CdSe nanoparticles can be dispersed well and have a good particle distribution.
We l e a d Thank you! Presented by Sin Khai Wen 116541/ School of Materials & Mineral Resources Engineering
We l e a d Back up Slides
We l e a d (a) (b) (c) Figure 20: (αhν)2 versus optical band gap of (a) CdSe at NTA concentration of 120mM, (b) CdSe at NTA concentration of 180mM, (c) CdSe at NTA concentration of 240mM Result and Discussion
We l e a d Result and Discussion Figure 21: EDX data of CdSe from 180mM NTA concentration deposited at 26 hours Morphology of CdSe
We l e a d 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 Currentdensity,J(mA/cm2) Voltage, V (v) Figure 22: Graph of current density-voltage for deposited CdSe from NTA concentration of 120mM 8h 14h 20h 26h Result and Discussion
We l e a d Result and Discussion 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0 0.05 0.1 0.15 0.2 0.25 Currentdensity,J(mA/cm2) Voltage, V (v) Figure 23: Graph of current density-voltage for deposited CdSe from NTA concentration of 180mM 8h 14h 20h 26h
We l e a d 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.05 0.1 0.15 0.2 0.25 Currentdensity,J(mA/cm2) Voltage, V (v) Figure 24: Graph of current density-voltage for deposited CdSe from NTA concentration of 240mM 8h 14h 20h 26h Result and Discussion
We l e a d 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.05 0.1 0.15 0.2 0.25 0.3 Currentdensity,J(mA/cm2) Voltage, V (v) Figure 25: Graph of current density-voltage for deposited CdSe multilayer from different NTA concentration and different time deposition 0.12mM 26h,0.18mM 14h 0.12mM 26h,0.24mM 8h 0.18mM 14h,0.12mM 26h 0.18mM 14h, 0.24mM 8h 0.24mM 8h,0.12mM 26h 0.24mM 8h,0.18mM 14h Result and Discussion

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Sin Khai Wen FYP Viva Presentation

  • 1. We l e a d Final Year Project 2015/2016 Final Year Project Title: Deposition and Characterization of CdSe Nanoparticles Multilayer on Conductive Substrate by Chemical Bath Deposition Final Year Project Viva Presentation Name: Sin Khai Wen No. Matric: 116541 Supervisor: Dr. Khatijah Aisha Bt. Yaacob
  • 2. We l e a d Introduction of CdSe • Important II-VI compound because of its size-dependent exceptional optoelectronic properties in the visible range • It has a direct bulk band gap (1.74 eV) with high absorption coefficient near the band edge, high photosensitivity, tunable band gap from around 450 to 700nm which cover the entire visible spectral range and quantum size effect, allow its use in thin film devices, especially for application in solar hybrid system. • Solar cell, light emitting diode, nano sensors, photo detectors Figure 1: Left, absorption spectra of differently sized CdSe nanocrystals. Right, corresponding PL spectra representing deeper red, red, orange, yellow, green and blue (from right to left) emitting CdSe cluster and nanocrystals under UV excitation at 380nm (Yuan & Krüger, 2012) Yuan, Y. & Krüger, M., 2012. Polymer-Nanocrystal Hybrid Materials for Light Conversion Applications. Polymers, Volume 4, pp. 1-19.
  • 3. We l e a d Introduction of Chemical Bath Deposition • Chemical bath deposition (CBD) is the simplest deposition technique that do not require sophisticated and costly instruments. • Extensively used for preparation of CdSe thin film because of its application as window layer material in solar cell fabrication • Chemical Reaction: Cadmium salt reacted with NTA to form complex Cd salt, Cd2+ + NTA [Cd(NTA)]2+ (1) Hydrolysis of potassium hydroxide in water gives OH- ions in solution according to the equation, KOH(s) + H2O(l) K+ (aq) + OH- (aq) + H2O (l) (2) Hence, from reaction of (1) and (2), it will give solid Cd(OH)2 formation. Cd2+ + 2OH-  Cd(OH)2 (s) (3) From the reaction of selenium and sodium sulfite, we will get equation (4), and when dissolving in [Cd(NTA)]2+ solution, the byproduct is (5) Na2SO3 + Se Na2SeSO3 (4) SeSO3 2- + OH- HSe- + SO4 2- (5) The overall reaction can be described as follow Cd(OH)2 (s) + HSe- CdSe + OH- + H2O (6) ,
  • 4. We l e a d Introduction of QDSSC Figure 2: Operating principle of a typical QDSSC (Jun, et al., 2013) • The electrons will enter into the conduction band (CB) of the QD and the hole remains in the valence band (VB). • The excited QD injects the electron from its CB into the CB of the wide band gap semiconductor (e.g. TiO2) and become oxidised. • The injected electron from the QD percolates through the porous TiO2 , reaches the conducting glass, travels through the external load, completes the circuit. • The oxidized QD is then restored (hole is filled with electron) when it is reduced by S2- from the electrolyte and in turn it is oxidized into S2- that diffuses to the counter electrode. Jun, H., Careem, M. & Arof, A., 2013. Quantum dot-sensitized solar cells-perspective and recent developments: A review of Cd chalcogenide quantum dots as sensitizers. Renewable and Sustainable Energy Reviews, Volume 22, pp. 148-167.
  • 5. We l e a d Problem Statement • The deposition process in CBD uses a controlled chemical reaction which result in the deposition of a nanocrystalline films by precipitation • Small crystal size leads to quantum size effect and increase in the optical band gap • The major problem of the CBD method is the difficulty to produce small CdSe nanoparticle on the substrate • Another problem is deposition of CdSe multilayer with different size of CdSe nanoparticles on the substrate
  • 6. We l e a d Research Objectives • To synthesis different CdSe nanoparticle size using chemical bath deposition method by changing parameters such as complex agent concentration. • To deposit two layer of CdSe nanoparticles with different particle size on fluorine doped tin oxide(FTO) substrate. • To determine and compare electrical properties of CdSe multilayer with CdSe single layer solar cell.
  • 7. We l e a d Methodology- Procedure FTO cleaning – 2-propanol Deposition of TiO2 mesoporous layer Deposition of CdSe on the mesoporous TiO2 thin films by using chemical bath deposition method Parameters: • NTA concentration • Deposition time • Deposition of multilayer CdSe thin film Characterization: • XRD • SEM • UV-Vis • EDX Synthesis of polysulfide electrolyteFabrication of Cu2S photocathode Solar cell assembly Characterization • Photo-electrochemical Measurement (I-V)
  • 8. We l e a d Methodology Figure 3: Polysulfide electrolyte Figure 4: Brass counter electrode after immersed in 37% HCl at 70°C for 45 minutes Figure 5: Cell assembly with polysulfide electrolyte injected between the two electrodes
  • 9. We l e a d Result and Discussion (a) (b) Figure 6: TiO2 thin films (a) before annealed and (b) after annealed TiO2 nanoparticle Pore Structure Figure 7: FESEM image of TiO2 mesoporous layer at magnification 30.00KX TiO2 Mesoporous Layer
  • 10. We l e a d Result and Discussion 0 0.5 1 1.5 2 2.5 340 390 440 Absorbance(a.u) Wavelength(nm) 0 5 10 15 20 25 30 35 40 3.2 3.3 3.4 3.5 3.6 (hv)2 optical band gap(eV) Figure 8: Absorbance spectra of TiO2 mesoporous layer Figure 9: (αhν)2 versus optical band gap
  • 11. We l e a d Result and Discussion Figure 10: CdSe solution with 240, 180 and 120mM NTA from left to right 240mM NTA 180mM NTA 120mM NTA CdSe Solution
  • 12. We l e a d Result and Discussion XRD Analysis of CdSe Nanoparticles Figure 11: XRD pattern of CdSe at different NTA concentration selenium oxide Figure 12: XRD pattern of CdSe quantum dots (Mahajan, et al., 2013) S.Mahajan, Rani, M., Dubey, R. B. & Mahajan, J., 2013. Characteristics and Properties of CdSe Quantum Dots. International Journal of Latest Research in Science and Technology, 2(1), pp. 457-459.
  • 13. We l e a d Sample Matching peaks (hkl) 2θ (degree) Spacing, d (Å) FWHM, β (°) Crystallite size (nm) 120mM NTA CdSe 111 24.27 3.66 0.620 13.00 180mM NTA CdSe 111 25.87 3.44 0.889 8.56 240 mM NTA CdSe 111 25.44 3.50 3.16 2.45 Table 1: Different parameters of different NTA concentration of CdSe nanoparticles obtained from XRD Result and Discussion Scherrer’s Equation to calculate crystallite size, D = 0.94λ β cosθ
  • 14. We l e a d Result and Discussion FTIR Analysis of CdSe Nanoparticles Figure 13: FTIR spectra of CdSe at different NTA concentration H bond (-OH group) C-H bondingCOO- stretchingC-O group, NTA exist Cd(OH)2 Zhang, A. et al., 2012. Suppressed blinking behavior of CdSe/CdS QDs by polymer coating. Nanoscale, pp. 1-8. Ingole, P. P. & Haram, S. K., 2010. Citrate-capped Quantum dots of CdSe for the Selective Photometric Detection of Silver Ions in Aqueous Solutions. Liu, I.-S.et al., 2008. Enhancing photoluminescence quenching and photoelectric properties of CdSe quantum dots with hole accepting ligands. Journal of Materials Chemistry, Volume 18, pp. 675-682. Corer, S. & Hodes, G., 1994. Quantum Size Effects in the Study of Chemical Solution Deposition Mechanisms of Semiconductor Films. J. Phys. Chem, Volume 98, pp. 5338-5346. To determine the existing of Cd(OH)2 because hydroxide crystal from Cd(OH)2 in solution, act as nuclei for formation of CdSe (Corer & Hodes, 1994).
  • 15. We l e a d Result and Discussion UV-Vis of CdSe nanoparticles with different concentration of NTA 0.4 0.6 0.8 1 1.2 400 500 600 700 Absorbance Wavelength(nm) 120mM NTA CdSe 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 400 500 600 700 Absorbance Wavelength(nm) 180mM NTA CdSe 0.4 0.6 0.8 1 1.2 400 500 600 700 Absorbance Wavelength(nm) 240mM NTA CdSe Figure 14: a) Absorption spectra of CdSe at NTA concentration of 120mM, b) Absorption spectra of CdSe at NTA concentration of 180mM, c) Absorption spectra of CdSe at NTA concentration of 240mM (a) (b) (c)
  • 16. We l e a d Average diameter, D= (1.6122x10-9)λ4-(2.6575x10-6) λ3+(1.6242x10-3) λ2-(0.4277) λ+41.57 (Peng, et al., 2003) Sample 120mM NTA CdSe 180mM NTA CdSe 240mM NTA CdSe Wavelength (nm) 608.94 554.98 587.48 Average Diameter (nm) 5.00 3.14 4.09 Band gap energy (eV) 1.93 2.10 1.95 Result and Discussion Table 2: Wavelength, average diameter and band gap energy of CdSe at different concentration Yu, W. W., Qu, L., Guo, W. & Peng, X., 2003. Experimental Determination of the Extinction Coefficient of CdTe, CdSe, and CdS Nanocrystals. Chemistry Material, Volume 15, pp. 2854-2860.
  • 17. We l e a d Result and Discussion 120mM NTA 180mM NTA 240mM NTA 8 hr 14 hr 20 hr 26 hr Figure 15: Deposited CdSe for 26 hours on FTO glass with different NTA concentration Figure 16: Deposited CdSe with NTA concentration of 240mM at different time Deposition of CdSe on TiO2 Mesoporous Layer
  • 18. We l e a d Result and Discussion Time deposition (hr) 10.0KX 30.0KX 8 14 20 26 Figure 17: FESEM image of CdSe from concentration of 180mM at different time under magnification of 10.0KX and 30.0KX
  • 19. We l e a d Result and Discussion NTA concentration (mM) Time deposition (hr) Short Circuit Current Density, Jsc (mA/cm2) Open Circuit Voltage, VOC (V) Fill factor, FF Efficiency, η (%) (x 10-2) 8 0.055 0.145 0.323 2.6 120 14 0.095 0.085 0.366 3.0 20 0.465 0.091 0.283 12.0 26 0.905 0.182 0.286 47.1 8 0.212 0.184 0.388 15.1 180 14 0.350 0.217 0.281 21.3 20 0.127 0.160 0.336 6.8 26 0.105 0.123 0.283 3.7 8 0.967 0.227 0.316 69.4 14 0.509 0.195 0.326 32.4 240 20 0.550 0.131 0.244 17.6 26 0.448 0.131 0.331 19.4 Table 3: Summary of short circuit current density, open circuit voltage and efficiency at 120mM,180mM and 240mM NTA concentration
  • 20. We l e a d Result and Discussion Deposition of CdSe Nanoparticles Multilayer on TiO2 Mesoporous Layer Figure 18: CdSe multilayer deposited with 1st layer is from 120mM NTA concentration at 26 hours and 2nd layer is from 180mM NTA concentration at 14 hours CdSe multilayer FTO glass fracture Figure 19: FESEM image of cross section image of CdSe multilayer on FTO glass at magnification of 1KX
  • 21. We l e a d First Layer Second Layer Short Circuit Current Density, Jsc (mA/cm2) Open Circuit Voltage, VOC (V) Fill factor, FF Efficiency, η (%) (x 10-2) NTA concentration (mM) Time deposition (hr) NTA concentration (mM) Time deposition (hr) 120 (b) 26 180 14 0.521 0.176 0.310 28.4 120 (b) 26 240 8 0.132 0.070 0.297 2.7 180 14 120 (b) 26 0.102 0.027 0.310 0.9 180 14 240 (b) 8 0.303 0.080 0.195 4.7 240 8 120 (b) 26 0.722 0.251 0.271 49.1 240 (b) 8 180 14 0.302 0.155 0.262 12.3 Result and Discussion Table 4: Summary of short circuit current density, open circuit voltage and efficiency for deposited CdSe multilayer at different NTA concentration and different time deposition * (b) means bigger average diameter of particles
  • 22. We l e a d Conclusion • By changing NTA complex agent concentration with 120mM, 180mM and 240mM, different CdSe nanoparticle size 5.00nm, 3.14nm and 4.09nm with band gap energy 1.93eV, 2.10eV and 1.95eV had been synthesized respectively. • For NTA concentration of 120mM, as time deposition increased, the efficiency also increased. However, for NTA concentration of 180mM and 240mM, overall efficiency decreased as the time deposition increase. • Two layer of CdSe nanoparticles with different particle size had been deposited on FTO substrate by CBD method. • However, 2nd layer deposition of CdSe did not enhance the overall cell efficiency
  • 23. We l e a d Recommendation • Ostwald ripening process in the CdSe solution gives low conversion efficiency of the cells. • The change in colour from yellow, orange and then finally red or dark red shown that CdSe nanoparticles growing bigger. • To avoid ostwald ripening, once the CdSe solution is synthesized, the substrate should be deposited at once so that the CdSe nanoparticles can be deposited onto substrate and nucleation takes place on the substrate before agglomeration occurs. • Higher temperature deposition can be carried out too so that the CdSe nanoparticles gain energy and will not agglomerate together. • Besides that, when the CdSe solution is not used, the solution should always be stirred so that the CdSe nanoparticles can be dispersed well and have a good particle distribution.
  • 24. We l e a d Thank you! Presented by Sin Khai Wen 116541/ School of Materials & Mineral Resources Engineering
  • 25. We l e a d Back up Slides
  • 26. We l e a d (a) (b) (c) Figure 20: (αhν)2 versus optical band gap of (a) CdSe at NTA concentration of 120mM, (b) CdSe at NTA concentration of 180mM, (c) CdSe at NTA concentration of 240mM Result and Discussion
  • 27. We l e a d Result and Discussion Figure 21: EDX data of CdSe from 180mM NTA concentration deposited at 26 hours Morphology of CdSe
  • 28. We l e a d 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 Currentdensity,J(mA/cm2) Voltage, V (v) Figure 22: Graph of current density-voltage for deposited CdSe from NTA concentration of 120mM 8h 14h 20h 26h Result and Discussion
  • 29. We l e a d Result and Discussion 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0 0.05 0.1 0.15 0.2 0.25 Currentdensity,J(mA/cm2) Voltage, V (v) Figure 23: Graph of current density-voltage for deposited CdSe from NTA concentration of 180mM 8h 14h 20h 26h
  • 30. We l e a d 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.05 0.1 0.15 0.2 0.25 Currentdensity,J(mA/cm2) Voltage, V (v) Figure 24: Graph of current density-voltage for deposited CdSe from NTA concentration of 240mM 8h 14h 20h 26h Result and Discussion
  • 31. We l e a d 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0.05 0.1 0.15 0.2 0.25 0.3 Currentdensity,J(mA/cm2) Voltage, V (v) Figure 25: Graph of current density-voltage for deposited CdSe multilayer from different NTA concentration and different time deposition 0.12mM 26h,0.18mM 14h 0.12mM 26h,0.24mM 8h 0.18mM 14h,0.12mM 26h 0.18mM 14h, 0.24mM 8h 0.24mM 8h,0.12mM 26h 0.24mM 8h,0.18mM 14h Result and Discussion