Transcript Polymer nano-crystal composites for telecom

Semi-conducting organic polymers
and
Inorganic semiconductor nano-crystals
Nir Tessler
EE Dept. Technion
Semiconducting Organic Polymers
The material:
Organic semiconductors =
molecular materials
small molecules to
long polymer chains.
Soluble Optoelectronic materials
(they come as powder or fibers. We
dissolve them in the appropriate solvent
and cast them from solution. We usually
design it such that after drying we get
0.1micron thick solid film)
Length scale:
Typical layer thickness –
50-100nm
Inter chain distance ~ 0.5nm
Nano-Materials
The original motivation
Going from green emission to
red emission via simple
“block” exchange
Chemistry LEGO
n
+
+
1
0.8
0.6
CN
0.4
0.2
CN
=
CN
n
0
400
500
600
700
Wavelength (nm)
Organic LEDs one of the best sources for visible light
800
900
The first known application
Organic (“plastic”) Displays
A proof for the material maturity:
Examples from the lab
Organic transistor
switching organic LED
Blue organic LED
A “Problem”
Polymers emit visible light only! But optical communication
elements operate with near infrared light  can’t use the low cost
“plastic” technology?
OK – Lets mix
PbSe
5 nm
5nm
InAs/ZnSe
O
Conjugated
polymers
MeO
n
Mix It
Organic polymer in solution
Inorganic semiconductor nano-crystals in
solution
oc4
oc10
oc4
*
n
o
*
OMe
n=o=0.5
Mix two solutions to get the right
composition
Using transmission electron microscope
we can also “see” the 5nm crystals in the
polymer matrix (i.e. the solid film)
After mixing, the plastic polymer do not emit visible light
and instead the inorganic nanocrystals emit in the near
infrared (telecomm bands)
Luminescence (a.u.)
Indium Arsenide nanocrystals
1000
Size A
Size B
1200
1400
Lead Selenide nanocrystals
Size C
1600
Wavelength (nm)
1800
1000
1200
1400
1600
1800
Wavelength (nm)
A nice feature – by changing the size of the nanocrystal it is possible to tune the
emission to a desired wavelength
What happens when you place such a composite film between two electrodes?
Ca\Al (cathode)
Current/Energy
is first
O
injected into the
Polymer
polymer
-
MeO
V
n
Energy/Charge
Transfer to the
nanocrystal
nanocrystal
+
Light Emission
PEDOT/ITO (Anode)
Glass
The potential Impact
The telecomm experts say that
for the fiber to the home to
happen they need low cost
components that can be
afforded by any household.
 Use “plastics”
Thanks