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…...