Current Research
• Bioelectronics
• Hybrid molecular/non-molecular, organic/inorganicMaterials & Interfaces
• ALTERNATIVE ENERGY
David Cahen 11/’12
Current Research
• Bioelectronics: Proteins as (Opto)Electronic Materials? Proteins as Organic NPs/core-shell QDs “Doping” Proteins
• Hybrid molecular/non-molecular, organic/inorganicMaterials & Interfaces
* Remaking Silicon and other Semicond.
• ALTERNATIVE ENERGY Chemistry & Physics of Light Electrical Energy conversion
* High voltage Solar Cells
David Cahen 11/’12
Research topicsMotivation• Understanding & Curiosity (“Everest” research)• Help Meet Energy Challenge• Blend Electronics with Biology
QUESTIONS:• (How) can organic molecules change electronics (also with
Kronik) ?• (How) can proteins be electronic materials (with M.
Sheves) ? Why doesn’t nature use electronic conduction ?
• What are the real limits to efficiency x lifetime) /cost of photovoltaic solar energy conversion? (with G. Hodes)
• (How) can we make Solar Paint?
David Cahen *12/’11
Solar Cell Concepts and MaterialsBasic science towards improving
(efficiency x lifetime) /cost of (any) solar cell
what are the real limits to PV energy
conversion ?
• Metal-Insulator-Semiconductor solar cells :
re-discovering Si
• Mesoporous, nanocrystalline solid junctions
high voltage solar cells (with G. Hodes)
CdS
CdTe
Adsorbed molecule
Adsorption at the PV junction - affects VOC ! ! !
Effects of molecule adsorption on solar cell performance
GlassConductive oxide
Poly-xtline p-CdTe
h
Poly-xtline n-CdSV
Back contact
Solar Cell Concepts and MaterialsMolecules as “door-men”
HOW IS THIS POSSIBLE ?
idealizedcartoon
SC Pinholes
Molecules
… because … of physics of dipole layers !
Even poorly organized monolayers can do,
but
need at least average orientation
i.e., we can use even discontinuous incomplete monolayers
idealizedcartoon
… because … of physics of dipole layers !
ACCEPTOR
DONOR
Device Outline
+
-+
-
+ l
+ l
+ l
+ l
+ l
+ l
VocVoc
Monolayer: Trimethoxy Silane
~1 nm
Metal Contact ~10 nm
Metal Contact
Donor : Organic Light Absorber ~40 nm
R R R R R R R R R R R R R R R R R
l l l l l l l l l l l l l l l l l l
use
or
R = Dipole-forming Molecules
with M. Bendikov, L. Kronik, R. Naaman A. Kahn (Princeton)
Which types of electronic conductors
do we know ?
Silicon Carbon Nanotubes
N
N N
N
HO O
Fe
Heme
β-CarotenePentacene
Cu
metals semiconductors
Diamond
Carbon
Organic(semi)conductors
Bio-molecules?
INORGANIC
ORGANIC
Electronics with Bio-Molecules?Electronic Conduction through Proteins & Peptides
What controls transport?
High quality
device structures
Transport
(yield, reproducibility) Spectroscopy
electronic, electricaloptical+++
TheoryElectron Transfer Models
Electronic structure
Transport mechanisms
+50 mV
Au
Lift off float on (LOFO) - Gold
0.2mm2 109 proteins/contact
Top Electrode Hg drop or “ready-made Au pad”
Hanging Hg drop
Cartoon!!
Protein Studies at single/few molecules level
A
10 nm
Metallic substrate
2 μm
(more)realistic
So … use MACROscopic protein monolayers
…..
…..
….. …..
…..
contact
…..
intimate 5 µm2 contact to a 0.5 nm2 /molecule monolayer ? contact each grass leaf (~3 cm2) on 70×100 m2 soccer field
[Akkerman]
but …still, higher over-all currents large measuring ability gain
Is also a Cartoon!!
-1.0 -0.5 0.0 0.5 1.0-8
-6
-4
-2
0
2
4
Cur
rent
( A
)
Bias Voltage (on metal) [V]
Az (on SH; ~Br)
-1.0 -0.5 0.0 0.5 1.0
1E-12
1E-11
1E-10
1E-9
1E-8
1E-7
1E-6
Cur
rent
(A
)
Voltage [V]
Az
-1.0 -0.5 0.0 0.5 1.0-8
-6
-4
-2
0
2
4
Cur
rent
( A
)
Bias Voltage (on metal) [V]
Az (on SH; ~Br) bR (on NH
2)
-1.0 -0.5 0.0 0.5 1.0
1E-12
1E-11
1E-10
1E-9
1E-8
1E-7
1E-6
Cur
rent
(A
)
Voltage [V]
Az bR
-1.0 -0.5 0.0 0.5 1.0-8
-6
-4
-2
0
2
4
Cur
rent
( A
)
Bias Voltage (on metal) [V]
Az (on SH; ~Br) bR (on NH
2)
BSA (on NH2)
-1.0 -0.5 0.0 0.5 1.0
1E-12
1E-11
1E-10
1E-9
1E-8
1E-7
1E-6
Cur
rent
(A
)
Voltage [V]
Az bR BSA
I-V characteristicsprotein layers
-1.0 -0.5 0.0 0.5 1.0-8
-6
-4
-2
0
2
4
Cur
rent
( A
)
Bias Voltage (on metal) [V]
Az (on SH; ~Br) bR (on NH
2)
BSA (on NH2)
OTMS (C18
)
-1.0 -0.5 0.0 0.5 1.0
1E-12
1E-11
1E-10
1E-9
1E-8
1E-7
1E-6
Cur
rent
(A
)
Voltage [V]
Az bR BSA OTMS
Conducting substrateLinker layer
Electrical top contact
Protein monolayer
Conducting substrate
contact
HSA vs. BSA
2 4 6 8 10 12 14 16
-17
-16
-15
-14
-13
ln
)J@
-0.0
5V
(
1000/T )K-1(
HSA BSA
Doping Proteins
0 5 10 15 20 25 30 35
-17
-16
-15
-14
-13
-12
-11
-10
ln
)J @
-0.0
5V
(
1000/T
HSA-RA 1-3
HSA-hemin
HSA-RA 1-2
HSA HSA-RA 1-1 HSA-RA 1-2 HSA-RA 1-3 HSA-hemin holo-Az
HSA
HSA-RA 1-1
holo-Az3.5
nm
4.4
n
m
HSA-hemin vs. Cyt C
0 5 10 15 20 25 30 35-16
-15
-14
-13
-12
HSA-hemin CytC electrostatic
ln)J
@-0
.05
V(
1000/T
85 meV90 meV
Doping Proteins
Temp. independen
t
Thermally activated
Electron Transport Mechanisms (bR)
Sepunaru et al., JACS 2012
OPEN QUESTIONS
• What are the basic solar light electricity limits? Needed for better cells / solar paint / high Voltage cells
Tailor solar cells with molecules
• The inorganic / organic, non-molecular / molecular interface, the next frontier for electronics?
• (How) can we use proteins as Bioelectronics building blocks? Why is Electron Transport across proteins so efficient ?
Study PeptidesUse also CP-AFM and ElectrochemistryStudy biological function effects (e.g., CO/O2 on myoglobin)Make new composite materials using protein / NP analogy
FURTHER collaboration in WIS with: R. Naaman, I. Lubomirsky, S.Cohen, H.Cohen, D. Oronin Israel with Technion, Bar Ilan U, Tel Aviv Uoutside Israel with Princeton, Wageningen, UNSW, UT Dallas, NREL, U. Cyprus, Chiba U…...