Smart Materials in Renewable Devices Dr. Pramod K Singh Sharda University, G. Noida, India E mail: pramodkumar.singh@sharda.ac.in http://pramodkumarsingh.weebly.com

Syllabus Materials- Basic Concepts 7.01 SMDXXX.A Unit A Materials- Basic Concepts 7.02 SMDXXX.A1 Unit A Topic 1 Classification of Materials, Bonding in solids 7.03 SMDXXX.A2 Unit A Topic 2 Crystal structure, Bravais lattice, Miller Indices 7.04 SMDXXX.A3 Unit A Topic 3 Imperfections of crystals 7.05 SMDXXX.B Unit B Dielectrics, Superconductors and Magnetic Materials 7.06 SMDXXX.B1 Unit B Topic 1 Dielectic materials and their properties 7.07 SMDXXX.B2 Unit B Topic 2 Superconductors and their applications 7.08 SMDXXX.B3 Unit B Topic 3 Magnetic materials and their properties

Syllabus Composite & Nanocomposite materials 7.09 SMDXXX.C Unit C Composite & Nanocomposite materials 7.10 SMDXXX.C1 Unit C Topic 1 Introduction of composite and Nanocomposite materials 7.11 SMDXXX.C2 Unit C Topic 2 Metal-Ceramic nanocomposite / Nanobiocomposites 7.12 SMDXXX.C3 Unit C Topic 3 Polymer based nanocomposites 7.13 SMDXXX.D Unit D Characterization Techniques 7.14 SMDXXX.D1 Unit D Topic 1 X-ray diffraction 7.15 SMDXXX.D2 Unit D Topic 2 UV-Visible spectroscopy 7.16 SMDXXX.D3 Unit D Topic 3 Infrared spectroscopy 7.17 SMDXXX.E Unit E Devices 7.18 SMDXXX.E1 Unit E Topic 1 Devices for energy conversion 7.19 SMDXXX.E2 Unit E Topic 2 Storage Devices 7.20 NSTXXX.E3 Unit E Topic 3 Sensors and Microelectronic devices

Marks Distribution Assignment Test Presentation Project/Att.

Application: Super Capacitors/DSSC

Materials Introduction Principle, construction and working of Ultracapacitor Advantage, disadvantage and application

Super Capacitor Capacitor is a device to store the charge in an electric circuit. Capacitor is made up of two conductors separated by an insulator called dielectric. The dielectric can be made of paper, plastic, mica, ceramic, glass, a vacuum or nearly any other nonconductive material. Some Capacitors are called Electrolytic in which the dielectric is aluminium foil conductor coated with oxide layer.

Ultracapacitor The electron storing capacity of capacitor is measured in Farads 1 farad is approximately the charge with 6,280,000,000,000,000,000 electrons. Definition:Ultracapacitors can be defined as a energy storage device that stores energy electrostatically by polarising an electrolytic solution.

Super Capacitor/Ultra Capacitor Unlike batteries no chemical reaction takes place when energy is being stored or discharged and so ultracapacitors can go through hundreds of thousands of charging cycles with no degredation. Ultracapacitors are also known as Double-layer capacitors/ Supercapacitors.

Principle, construction and working Energy is stored in ultracapacitor by polarizing the electrolytic solution. The charges are separated via electrode –electrolyte interface. Current Collector Electrolyte Separator +

Supercapacitor Construction Ultracapacitor consist of a porous electrode, electrolyte and a current collector (metal plates). There is a membrane, which separates, positive and negative plated is called separator. The following diagram shows the ultracapacitor module by arranging the individual cell C1 C2 C3 C4 C5 Ultracapacitor stack + --

Super Capacitor; Working Principle There are two carbon sheet separated by separator. The geometrical size of carbon sheet is taken in such a way that they have a very high surface area. The highly porous carbon can store more energy than any other electrolytic capacitor. When the voltage is applied to positive plate, it attracts negative ions from electrolyte. When the voltage is applied to negative plate, it attracts positive ions from electrolyte.

ULTRA CAPACITOR

ULTRA CAPACITOR Therefore, there is a formation of a layer of ions on the both side of plate. This is called ‘Double layer’ formation. For this reason, the ultracapacitor can also be called Double layer capacitor. The ions are then stored near the surface of carbon. The distance between the plates is in the order of angstroms. According to the formula for the capacitance, Dielectric constant of medium X area of the plate Capacitance = ----------------------------------------------------------------- Distance between the plates

ULTRA CAPACITOR Ultracapacitor stores energy via electrostatic charges on opposite surfaces of the electric double layer. The purpose of having separator is to prevent the charges moving across the electrodes. The amount of energy stored is very large as compared to a standard capacitor because of the enormous surface area created by the (typically) porous carbon electrodes &the small charge separation (10 A0 ) created by dielectric separator

------------------------ Diagram shows the formation of double layer ------------------------ ++++++++ +  Electrolyte Separator Electric double layer ▬

Super Capacitor: Advantage Long life: It works for large number of cycle without wear and aging. Rapid charging: it takes a second to charge completely Low cost: it is less expensive as compared to electrochemical battery. High power storage: It stores huge amount of energy in a small volume. Faster release: Release the energy much faster than battery.

Super Capacitor: Disadvantage They have Low energy density Individual cell shows low voltage Not all the energy can be utilized during discharge They have high self-discharge as compared to battery. Voltage balancing is required when more than three capacitors are connected in series.

Super Capacitor: Applications They are used in electronic applications such as cellular electronics, power conditioning, uninterruptible power supplies (UPS), They used in industrial lasers, medical equipment. They are used in electric vehicle and for load leveling to extend the life of batteries. They are used in wireless communication system for uninterrupted service. There are used in VCRs, CD players, electronic toys, security systems, computers, scanners, smoke detectors, microwaves and coffee makers.

Solid State Solar Cell (SSSC) * Different conduction mechanism * Charge separation ☞ to form M-S (Schottky) junctions Advantage High efficiency (~24 %) Disadvantage High cost both type of semiconductors are prepared from highly pure semiconductor by a severely controlled doping process

Classification & Principle Si: mono, poly and amorphous-crystalline Inorganic Solar Cell GaAs, InP, CdTe GaAs/Ge Organic Solar Cell Dye Sensitized Solar Cell Conducting polymer - fullerene Conducting polymer - conducting polymer Organic polymer - nanoinorganic materials ☞Basic Principle charge separation at the junction (interface) of two materials of different conduction mechanism

Components of DSSC TiO2 electrode with Dye Electrolyte with redox couple Counter electrode I- I3- External Circuit - TCO conducting glass Crystalline TiO2 Sensitizer dye Polymer electrolyte

Dye-Sensitized Solar Cells TCO Glass) Electrolyte Cathode( TCO Glass） e- I-/I3- e- (Semiconductor) Anode (Electrolyte) (Dye) TiO2 Low Cost Good Recyclability Wide Variation High Energy Conversion Efficiency Promising Candidate for Next Generation Solar cell !?

Role of redox couple in DSSC * boys as electron * filled boat as iodide * empty boat as triiodide Nam- Gyu Park and K. Kim, Phys. Stat. Sol. (a), 205 (2008) 1895

DSSC: Electrolyte Electrolyte in DSSC Polymer Electrolytes re-reduction of the oxidized dye transferring ion oxidized by contact with electrode Electrolyte in DSSC Liquid Electrolytes Ion Conducting Gels leakage evaporation of the solvent volatile liquid encapsulated in the gel pores leakage evaporation of the solvent Alternative Polymer Electrolytes

Preparation of Polymer Electrolytes with IL Mixed PEO, KI and I2 in acetonitrile to get PEO:KI/I2 polymer electrolyte 2. Added ionic liquid in the polymer electrolyte solution 3. Stirred continuously 4. Cast electrolyte solution in polypropylene dishes 5. Dried these films under vacuum to remove the traces of solvent

Preparation of DSSC with Polymer Electrolytes/ IL 6. Prepared nanocrystalline TiO2 electrode by chemical sintering method and sensitized (24 hrs.) into Dye solution. 7. Casted polymer/IL solution (~400 μL)on TiO2 surface followed two step cast method. 8. Sandwitched electrolyte solution between TiO2 and counter electrode. 9. Dried the cell under vacuum (~2 days) to remove the traces of solvent.

Fabrication of DSSC with PE/IL as electrolyte TiO2 electrode FTO glass 2x1.5 cm2 Blocking layer coating 500 0C for 30 min in furnace Cut 30x30 cm2 CE Wash Pt layer coating 400 0C for 30 min in furnace Two Scotch tape Thickness ~ 50 ㎛ Dye Sensitization (~ 24 hrs] Sintering in furnace 500 0C for 30 min TiO2 paste using Doctor blade TiO2 electrode PE/IL casting (2 step) TiO2 sensitized with dye PE/IL solid electrolyte CE TiO2 electrode with Dye

Characterizations SEM (for TiO2 surface and particle size) TEM XRD Impedance spectroscopy (for σ) DSC (for check crystallinity) J-V Characteristics (to see solar cell performance)

SEM Measurement mesoporous TiO2 layer (30 min. sintering at 5000 C) cross sectional view top view

TEM Measurement Scrapped TiO2 powder TEM: *TiO2 particle size ~ 25 nm *Pore diameter ~10-15 nm *Pore wall mostly crystalline Pore

XRD Measurement ☞ S (Substrate FTO peaks) at ☞*A (Anatase TiO2 peaks) at 25.30, 38.60, 480, 53.90, 55.10 (101),(112),(200),(105),(211) [JCPDS# 211272] **Average size(TiO2) ~26 nm (Scherrer Formula) ☞ S (Substrate FTO peaks) at 26.60, 33.90, 430, 51.70, 54.80 (110),(101),(210),(211),(220) [JCPDS# 211250]

Polymer Electrolyte Film: Fabrication PEO in Methanol Added KI & I2 COMPLEXATION Stirred 24 hrs. in a Beaker at 50 0 C Clear PEO:KI/I2 solution. Thorough Mixing Ionic Liquid Pour in Petridish & Solution casting Dry Polymer Film

Conductivity Measurement Impedance Spectroscopy (for σ) σ = G X L / A G: conductance of the sample L: thickness of the sample A: the area of the sample

Electrical Conductivity:PEO:KI/I2+EMImSCN Composition σ (S/cm) PEO:KI/I2 (EO/K=17) 8.80 x 10-6 PEO:KI/I2 + 20 wt% IL 1.39 x 10-5 PEO:KI/I2 + 40 wt% IL 1.90 x 10-5 PEO:KI/I2 + 60 wt% IL 5.99 x 10-4 *PEO:KI/I2 + 80 wt% IL 7.62 x 10-4 * After that composition film was not stable

Electrical conductivity PEO:KI/I2+EMImSCN (IL) doping of IL increased σ attained max. σ at 80 wt% IL concentration After 80 wt% IL concentration, we could not get free standing polymer electrolyte film

XRD complete complexation reduced in crystallinity no additional peaks of KI in c

XRD: Effect of IL (PEO crystalline peaks 19o and 23.1o) The Intensity of PEO crystalline peaks decreased after adding KI and IL ► Incorporation of IL reduced crystallinity ► no new peaks appeared in (PEO:KI/I2)+80 wt% IL

DSC : Crystallinity Crystallinity χ (%) = ∆Hf / ∆Hf0 ∆Hf0 of 100 % crystalline PEO film was assumed 188.1J/g. [Polymer., 37, 5109 (1996)] Composition Tm (0C) ∆Hf (J/g) χ (%) a. PEO:KI/I2 (EO/K = 17) 60.34 86.38 45.94 b. PEO:KI/I2 + 40 wt% IL 51.71 29.06 15.45 c. PEO:KI/I2 + 80 wt% IL 45.00 16.18 8.60

J-V Characteristics Voc (V) FF (%) η (%) (using stable polymer films as electrolytes) Jsc (mA/cm2) Voc (V) FF (%) η (%) a 0.22 0.74 77.4 0.1 b 0.32 0.67 56.0 c 0.78 0.65 68.3 0.3 d 1.88 0.63 50.7 0.6 (PEO:KI/I2) + x wt% IL (a) x = 0, (b) x = 20, (c) x = 60, (d) x = 80

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