gr¤tzel photoelectrochemical solar cells from sunlight to electricity
TRANSCRIPT
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Grätzel Photoelectrochemical Solar Cells From Sunlight to Electricity
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Overview
i. Introduction to Grätzel Photoelectrochemical Solar Cells ii. How to make Grätzel solar cells iii. GCSE & AS/A-Level National Curriculum iv. GCSE & AS/A-Level
Investigations/Coursework
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i. Introduction to Grätzel Photoelectrochemical Solar
Cells
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Why Grätzel Photoelectrochemical Solar Cells?
Grätzel – Inventor Michael Grätzel and his researchers at Swiss Federal Institute of Technology in Switzerland
Photoelectrochemical – Electrochemical reactions involved (iodide electrolyte )
Solar – Absorption of sunlight energy in the visible region of the spectrum
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First Published Paper
Brian O’ Regan & Michael Grätzel., Nature, A low cost, high efficiency solar cell based on dye sensitised colloidal TiO2 films, 353, 1991
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What are Grätzel solar cell?
They are dye-sensitised titanium dioxide (TiO2) photo-
electrochemical cells that directly convert solar energy to electrical
energy
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What do they look like?
1) Top Plate (-ve), Organic dye adsorbed onto a coated layer of TiO2 2) Bottom Plate (+ve), Coated with graphite
1 2
1 2
Grätzel Cell
Two conducting glass plates sandwiched together between iodide electrolyte
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Schematic of Grätzel Solar Cell
TiO2 Layer
Dye adsorbed onto TiO2 particles
Iodide Electrolyte
Graphite layer
ITO conducting glass plate
ITO conducting glass plate
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How do they work?....
e-
dye e-
e-
e-
I- I3-
e-
Solar Energy
(1)
(2) (3)
(4)
TiO2
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Contd….. How do they work? 1) Sunlight energy (photoelectric effect) strike dye
molecules, exciting electrons 2) The excited electrons move through the conduction
band of TiO2 up to the conducting plate. Flow of electricity is initiated.
3) The dye is regenerated by the Iodide molecule giving up one of its electrons to form triiodide (oxidation occurs).
4) The triiodide molecule is reduced back to iodide by an electron at graphite conducting plate.
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ii. How to make Grätzel solar cells
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Steps to Making Grätzel Solar Cells
Step 1 & 2 - Preparation of plates Step 1 - + ve plate, coating with Graphite Step 2 - - ve plate, coating with TiO2 Step 3 - Adsorption of Dye onto TiO2 layer Step 4 - Assembly of Grätzel Solar Cell
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Step 1 - Preparation of graphite plate (+ve)
Coated with Graphite
Using a Pencil
Uncoated Conductive Glass plate
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Step 2 - Preparation of TiO2 plate (-ve)
1) Titanium dioxide powder and paste mix
2) Sintered @ 450 C for 30 minutes
(Pre-made TiO2 plates are also available)
Coated with TiO2
Uncoated Conductive Glass plate
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Titanium Dioxide
Support material (10um thick) Large Surface Area (Nanoparticles ~30nm) High Porosity Electron acceptor Electron conductor Numerous Advantages (i.e. cheap, abundant, non -toxic)
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Step 3 - Adsorption of Dye onto TiO2 coated plates
TiO TiO 2 2 coated plates adsorbing the dye
TiO TiO 2 2 coated plates Hybiscus tea leaves
boiled in water
Rinsed & Dried Rinsed & Dried
10mins 10mins
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Organic dyes
Various organic dyes can be used…………….
Hybiscus Tea (supplied in kits) Ribena Turmeric Powder Tea Cranberries Onion Skin Raspberries
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Step 4 - Assembly of Grätzel Solar Cell
Solar cell is made !!!!
Paperclip Clamp
(1)
(2)
Iodide Electrolyte
+ +
_
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Electrolyte
Potassium Iodide Regenerates the Dye
D + (adsorbed on TiO2) + 3/2 I- D (adsorbed on TiO2) + 1/2 I3
-
I3- + 2e- 3I- At Cathode
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Grätzel Cell Demonstration Kits
Each kit allows the students to prepare six solar cells to power a small electronic calculator
Website: www.mansolar.com
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Power a Calculator
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iii. GCSE & A-Level National Curriculum
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GCSE - National Curriculum
Photosynthesis – How Grätzel solar cells use an analogous mechanism to photosynthesis for energy conversion
Energy - Renewable and Non Renewable Sources
Electricity – Ohms Law, Power, Electrical Circuits
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i.e Photosynthesis & Solar Cells
SUN Chlorophyll
Hybiscus Tea
e- e-
e- e-
Electrical Energy
Chemical Energy
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A-Level - National Curriculum
Biology: Photosynthesis – Use of an analogous mechanism to dye sensitised solar cells Physics: Electricity, Energy & Power
Chemistry: Redox Chemistry - The mechanism of energy conversion in solar cells Materials Chemistry - Substrates utilised for making solar cells Alternative Energy - Combustion and/or environmental chemistry UV- Vis Spectroscopy - Light Absorption Transition metal complexes - Dye molecules utilised
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iv. GCSE & A-Level
Investigations/Coursework
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GCSE – Lower Tier Investigations / Coursework
1. To investigate the effect of voltage on increasing the number of solar cells in a series/parallel circuit
2. To investigate the effect of voltage/current on using different organic dyes
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GCSE- Higher Tier Investigations / Coursework
1. To investigate the power output (P=IV) of Grätzel
Solar cells on
i. varying the number of solar cells in a series/parallel circuit
ii. using different types of light bulbs for illuminating the solar cells (halogen, incandescent and fluorescent)
iii. using various soaking times for adsorbing the dye onto the TiO2
iv. varying the intensity of light
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Biology - A-level Investigations / Coursework
To compare the mechanisms of energy conversion in photosynthesis and Grätzel solar cells and investigate the effects of power efficiencies using chlorophyll and other related organic/inorganic dyes in Grätzel solar cells
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Physics & Chemistry - A-level Investigations / Coursework
1. To investigate the power efficiency of Grätzel solar cells using
a. Various soaking times for adsorbing the dye onto TiO2
b. Various light intensities c. Various organic/inorganic dyes d. Various types of TiO2 based materials (i.e. toothpaste, paint) e. Various coloured lights