Electricity from Light:

1
Electricity from Light The Grätzel Cell
2
Electromagnetic Spectrum
Increasing Energy Decreasing Wavelength
10-16 10-12 10 -02 10
-8 10 -6 10 -4
10 --2 10 0 10 2 10 4
10 8 l (m)
g-rays
X-rays
UV
IR
FM
AM
Long Radio Waves
Microwave
Radio Waves
400 500 600
700 Wavelength (l) in nanometers
3
Atomic Structure
4
Molecular Structure
5
Subtractive Coloration
If one component of white light is removed, the
color registered by the eye is the complimentary
color (opposite of the color removed).
6
Donor-Acceptor Concept
Dye molecules can be broken into three separate
pieces
Electron Donor Group
Electron Acceptor Group
Bridge
Electronegative elements Polar with d-
opposite bridge end. Cations
A place for the e- to move into higher
energy states. Usually part of The donor group
Lone e- pairs Anions Polar with d- at
bridge end
7
Donors
Increasing order of efficiency
8
Acceptors
Increasing order of efficiency
9
H2O
10
UV/ Visible Spectrophotometer Scan
A b s o r b a n c e
1.0
0.8
0.6
0.4
0.2
0.0
350
400
450
500
550
600
650
700
750
Wavelength in nanometers
11
What would happen if the electrons in the
dye molecule where captured and sent through
a curcuit?
12
Preparation of a Grätzel Cell
ISC 20 mA/cm2 VOC 0.7 Volts ?
1 Efficiency 11
Diagram courtesy of Dr. Wamser
13
Operation of a Grätzel Cell
Diagram courtesy of Dr. Wamser