Current Research
David Cahen 11/’12
• Bioelectronics
• Hybrid molecular/non-molecular, organic/inorganic
Materials & Interfaces
• ALTERNATIVE ENERGY
Current Research
David Cahen 11/’12
• Bioelectronics: Proteins as (Opto)Electronic Materials?
Proteins as Organic NPs/core-shell QDs
“Doping” Proteins
• Hybrid molecular/non-molecular, organic/inorganic
Materials & Interfaces
* Remaking Silicon and other Semicond.
• ALTERNATIVE ENERGY
Chemistry & Physics of Light  Electrical Energy conversion
* High voltage Solar Cells
Motivation
•
•
•
Research topics
David Cahen *12/’11
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) ?
•
What are the real limits to efficiency x lifetime) /cost
of photovoltaic solar energy conversion? (with G. Hodes)
(How) can we make Solar Paint?
•
Why doesn’t nature use electronic conduction ?
Solar Cell Concepts and Materials
Basic 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)
Solar Cell Concepts and Materials
Molecules as
“door-men”
V
Effects of molecule adsorption
on solar cell performance
Adsorbed molecule
CdTe
CdS
Back contact
Poly-xtline p-CdTe
Poly-xtline n-CdS
Conductive oxide
Glass
h
HOW IS THIS POSSIBLE ?
Adsorption at the PV junction
- affects VOC ! ! !
… because … of physics of dipole layers !
Molecules
SC
idealized
cartoon
Pinholes
… because … of physics of dipole layers !
i.e., we can use even
discontinuous incomplete monolayers
idealized
cartoon
Even poorly organized monolayers can do,
but
need at least average orientation
with M. Bendikov, L. Kronik, R. Naaman
A. Kahn (Princeton)
Device Outline
R = Dipole-forming Molecules
+
DONOR
l
l
l
l
+
Metal Contact
l
+
l l l l l l l l l l l l l l l l l l
+
~1 nm
+
R Monolayer:
R R R R R R Trimethoxy
R R R R R R Silane
R R R R
+
~40 nm
+
Donor : Organic Light Absorber
-
or
Voc
l
~10 nm
+
Metal Contact
-
use
ACCEPTOR
Which types of electronic conductors
do we know ?
Cu
Silicon
metals
semiconductors
Diamond
Carbon Nanotubes
Carbon
INORGANIC
ORGANIC
β-Carotene
Pentacene
Organic
(semi)conductors
Bio-molecules?
Heme
Electronics with Bio-Molecules?
Electronic Conduction through Proteins & Peptides
What controls transport?
High quality
device structures
Transport
(yield, reproducibility)
Theory
Electron Transfer Models
Electronic structure
Transport
mechanisms
Spectroscopy
electronic, electrical
optical +++
Top Electrode
Hg drop or “ready-made Au pad”
Au
Hanging Hg drop
0.2mm2
Lift off float on (LOFO) - Gold
109 proteins/contact
Protein Studies at single/few molecules level
2 μm
 So … use MACROscopic protein monolayers
A
Cartoon!!
10 nm
Metallic substrate
(more)
realistic
but …
still, higher over-all currents  large measuring ability gain
…..
…..
contact
…..
…..
…..
…..
Is also a Cartoon!!
intimate 5 µm2 contact to a 0.5 nm2 /molecule monolayer ?
contact each grass leaf (~3 cm2) on 70×100 m2 soccer field [Akkerman]
contact
I-V characteristics
protein layers
Protein monolayer
Electrical top contact
Conducting
substrate
4
4
2
2
2
OTMS (C18)
0
0
-2
-2
Current
Current(A)
(A)
Current
Current (( A)
A)
Linker layer
Conducting substrate
Az
Az (on
(on SH;
SH; ~Br)
~Br)
bR
bR (on
(on NH
NH22))
BSA
BSA (on
(on NH
NH2))
-4
-4
-6
-6
-8
-8
-1.0
-1.0
-0.5
-0.5
1E-6
1E-6
1E-7
1E-7
1E-8
1E-8
1E-9
1E-9
1E-10
1E-10
1E-11
1E-11
1E-12
1E-12
-1.0
-1.0
0.0
0.0
-0.5
-0.5
0.0
0.0
Voltage [V]
Voltage [V]
Az
Az
bR
bR
BSA
BSA
OTMS
0.5
1.0
0.5
1.0
0.5
0.5
Bias
Bias Voltage
Voltage (on
(on metal)
metal) [V]
[V]
1.0
1.0
Doping Proteins
HSA
HSA-RA 1-1
HSA-RA 1-2
HSA-RA 1-3
HSA-hemin
holo-Az
3.5 nm
-10
HSA-RA 1-3
-11
ln(J @-0.05V)
-12
holo-Az
-13
HSA-hemin
-14
HSA-RA 1-2
-15
HSA-RA 1-1
-16
HSA
-17
HSA
BSA
-13
HSA vs. BSA
5
10
15
20
25
30
35
1000/T
4.4 nm
ln(J@-0.05V)
-14
0
-15
-16
-17
2
4
6
8
10
12
-1
1000/T (K )
14
16
Doping Proteins
HSA-hemin
CytC electrostatic
ln(J@-0.05V)
-12
HSA-hemin vs. Cyt C
-13
-14
90
meV
85 meV
-15
-16
0
5
10
15
20
1000/T
25
30
35
Electron Transport Mechanisms (bR)
Temp.
independent
Sepunaru et al., JACS 2012
Thermally
activated
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 Peptides
 Use also CP-AFM and Electrochemistry
 Study 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. Oron
in Israel with Technion, Bar Ilan U, Tel Aviv U
outside Israel with Princeton, Wageningen, UNSW, UT Dallas, NREL, U. Cyprus, Chiba U…...