From Nanomolecular Junction to Nano-structured Semiconducting Polymer Organic Solar CellsPolymer Organic Solar Cells

Luping YuDepartment of Chemistry The University of Chicago

NSF Nanoscale Science and Engineering Grantees Conference12/07/2010

Semiconductor p-n junction

Sequential assembling of new diode molecule and related STM topography

S S

Me Me

SMe3SiN

S

N

S

Me Me

S CNS S S S

NaOCH3, THFGold film

dodecanethiolate SAM

S S

Me Me

SMe3SiN

S

N

S

Me Me

S Au film

on Au (111)mica

(Bu)4NFGold Nanoparticle solution.

S S

Me Me

SN

S

N

S

Me Me

SAu Au film

Control Electron Transport Through Sequential Assembly of Diode Molecules

0.0

0.2

0.4

A) b

0.0

0.2

0.4

A) b

S S SS S

i

S

iS

S

S

N

S

S N

S

S

S

S

NS

SN

S

S S SS S

i

S

i

-0 8

-0.6

-0.4

-0.2

Cur

rent

(n 5 pA 10 pA 25 pA 50 pA 75 pA 100 pA150 pA-0 8

-0.6

-0.4

-0.2

Cur

rent

(n 5 pA 10 pA 25 pA 50 pA 75 pA 100 pA150 pA

STS measurement setup for the assembly of diode molecules-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

-1.0

-0.8C

VBias (V)

150 pA 200 pA

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

-1.0

-0.8C

VBias (V)

150 pA 200 pA

0 2

0.3

0.4

0.5

-0.1

0.0

0.1

0.2

A)

0.6

0.8 50 pA 100 pA 200 pA 300 pA 400 pA500 pA

(nA

)

0.6

0.8 50 pA 100 pA 200 pA 300 pA 400 pA500 pA

(nA

)-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

-0.1

0.0

0.1

0.2

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

-0.5

-0.4

-0.3

-0.2

Cur

rent

(nA

0.0

0.2

0.4 500 pA 600 pA 700 pA 800 pA

Cur

rent

0.0

0.2

0.4 500 pA 600 pA 700 pA 800 pA

Cur

rent

V

Bias(V)V

Bias(V)

Opposite rectification direction was obtained when the orientation of diode molecule changed

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

-0.2

VBias (V)

a-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

-0.2

VBias (V)

a

Studies of Infrared Spectroscopy

vibr

atio

nN N

NC0.02 Si-C

H3

defo

rmat

ion

N NS S

SiMe3

Na+EtO-AuC-H

sym

.

N

N

N

NS S

SiMe3

x 100

x 100

x 100

N NS S H

F-

800 1000 1200 1400 1600 1800

Wavenumber (cm-1)

N N

Ch t i ti f th A bl STM i

bb

Characterization of the Assembly: STM microscopy

a ba b c

10 nm 50 nm 10 nm10 nm 50 nm 10 nm 10 nm

C t t t STM t h f ( ) d d thi l/1 SAMConstant-current STM topography of (a) dodecanethiol/1 SAM on Au(111) after attachment of Au NP to the top termini of 1. Inset: High-resolution image of the DDT SAM. (b). Image of a single

AuNP (c) molecule with (yellow circle) and without (green circle)AuNP. (c) molecule with (yellow circle) and without (green circle) AuNP STM imaging conditions: VBias=+1.0 V, It=1 pA

Effect of Protonation

SN N

N N

S

N N

N N

S

H+

H

S S S S SSSSS S S S S SSSSS

+H+

-H+

0.10 100 Before protonation

S S S S S S SSSSS

-0.2

-0.1

0.0

nt (n

A)

+H+0.050

0.075

0.100 p After deprotonation

nt (n

A)

-0 6

-0.5

-0.4

-0.3

Cur

ren

H+

-0.025

0.000

0.025

Cur

re

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5-0.6

VBias (V)-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

VBias (V)

Photovoltaic Effect of Monolayer of Molecular Diode Array Solar Cell

Diode array assembly

S

Au transferred by Stamp

NNArea: 50 x 50 m2

at 95 kN N

S S S S SSSSS

Au substrate

Molecular Wire Array

S

Molecular Wire Array

S

S

S

S S S SSSSS S

Solar Energy

Illustration by Peter Schrankhttp://www.economist.com/displayStory.cfm?story_id=14082027

http://www.rise.org.au/info/Applic/Solarpump/index.html

Organic and Organic/Inorganic Hybrid PVExciton ExcitonExciton

Light

ExcitonExciton Dissociation

Charge Transport

Hopping

+_

• Low cost, easy processing, and flexibility.

D A D+ A-

• Factors to be considered;

I. Efficient light absorption in whole solar spectrum-Low band gap.II Efficient exciton dissociation Proper driving force for the chargeII. Efficient exciton dissociation-Proper driving force for the charge

separation; energy level match between donor and acceptor.III. Effective charge transport-Balanced carriers’ mobility and

effective overlap.IV. Maximized Voc-HOMO of donor and LUMO of acceptor.

10

A ti l f i l llActive layers of organic solar cells.

Donor-acceptor Bulk heterojuction Idealized solar cellDonor acceptordouble layers1986, Tang.

Bulk heterojuctione.g. P3HT/PCBM

Idealized solar cellactive layerself-assembly

Novel Semiconducting Polymers Exhibiting High Solar Conversion Efficiency

S

COOC12H25

S

S

OC8H17

Sn SnPd(0)(PPh3)4

DMF/Toluene 110 oCn + n

S BrBrS

OC8H17

DMF/Toluene, 110 C

1.6

PTB1 l ti

120 b

0.8

1.2

PTB1 solution PTB1 film PTB1-PCBM blend film

zed

ABS 80

120 b

PTB1 film PTB1/PC61BM film

ount

s (a

.u.)

0.6

0.8

1.0

P3HT Film P3HT Solution

ized

AB

S300 400 500 600 700 800

0.0

0.4

Nor

mal

i

700 800 900 1000

0

40

Pho

ton

co

400 600 8000.0

0.2

0.4

Nor

mal

W l th ( )

12

300 400 500 600 700 800

Wavelength (nm)

700 800 900 1000

Wavelength (nm)Wavelength (nm)

Solar Cell composition, Structure and Their Performances

O

O

S

OC8H17

S

Al

S

OC8H17S

C12H25OOC

n

Ch t i ti

PTB1 PC61BM

Characteristics

Jsc = 12.5 mA/cm2, Voc = 0.57 V FF = 0.55 PCE = 4.8 % PCE 4.8 %

13

Solar Cell Performances with Different AcceptorsOC8H17

CaS

S

OC8H17

S

S

n

C12H25OOC

PTB1

PCE = 5.6%

14

Explanation for the good properties of PTB11.6

PTB1 solution

0.8

1.2

PTB1 solution PTB1 film PTB1-PCBM blend film

orm

aliz

ed A

BSReasons:1. Close to optimal band-gap at 1.6 eV.

300 400 500 600 700 8000.0

0.4

No

Wavelength (nm)

1 0

0.4

0.6

0.8

1.0

P3HT Film P3HT Solution

mal

ized

AB

S2. Planarity and rigidity of polymer chain-UV/vis spectra did not change much.

400 600 8000.0

0.2Nor

m

Wavelength (nm) 3. Balanced mobility 4.5×10-4 cm2/v.s

1.0

1.5

2.0

5 (A0.

5 /cm

)

l=65 nm l=100 nm

3 y 4 5 /vs P3HT 2.7×10-4 cm2/v.s. as indicated by the high fill factors.

0 1 2 3 40.0

0.5

J0.5

Vap-Vbi-Vr (V)

4. Preferred interpenetrating network

TEM image of PTB1/PCBMAFM i f PTB1/PCBM TEM image of PTB1/PCBMAFM image of PTB1/PCBM

16

5. Favored Charge separation Dynamics-TA spectra of PTB11. the visible 2. NIR region after 600 nm

4

-2

0

2

PTB1a

3 0

3.5

4.0

4.5

PTB1b

light excitation.

12

-10

-8

-6

-4

0.5 ps 1 ps 10 ps 100 ps

A (O

D)

1 0

1.5

2.0

2.5

3.0

A

(OD

)

500 550 600 650 700 750-16

-14

-12p

500 ps

Wavelength (nm)

900 1000 1100 1200 1300 1400 1500 16000.0

0.5

1.0

Wavelength (nm)1

3 5

PTB1/PCBM

PTB1/PCBM-2

-1

0

1

c2.5

3.0

3.5d

-6

-5

-4

-3

A

(OD

)

1.0

1.5

2.0

A

(OD

)

500 550 600 650 700 750-8

-7

Wavelength (nm)900 1000 1100 1200 1300 1400 1500 1600

0.5

Wavelength (nm)

6. Favored polymer chain packing-X-ray scattering studies

PTB1 film PTB1/PCBM composite a. In-plane linecuts of GISAXS.

PTB1PTB1/PCBM 1:1a

1000

10000 PTB1/PCBM 1:2PTB1/PCBM 2:1

Inte

nsity

1800

0.01 0.110

100

q (A-1)

800

1000

1200

1400

1600

1800

PTB1PTB1/PCBM 1:1PTB1/PCBM 1:2PTB1/PCBM 2:1PTB1/PCBM annealed

nten

sity

b

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.00

200

400

600

800In

1q (A-1)(b) Out-of-plane line-cuts of GIWAXS.

7. Favored charge transfer complex dissociation-Magnetic Field Effect on Photocurrent

12ITO/PEDOT/Polymer/Al

2.5P3HT:PCBM=1:0.8 PTB1

ITO/PEDOT/Polymer:PCBM/Ca/Al

g

PTBx

-2-101

P3HT PTB1PTB2M

FP (%

)

1.01.52.0

0 3006009000.00.20.40.60.81.0

-2V0V

MFP

(%)

Magnetic field (mT)

MFP

(%)

PTB1 PTB2

0V

PTBx

(PTB)1 (PTB)3Light excitation

Exciton dissociation

0 300 600 900-4-32 PTB2M

M ti fi ld ( T)0 300 600 900

0.00.5

-2VM

(e- h+)1 (e- h+)3

Exciton dissociation

Meganetic field (mT) Magnetic field (mT)

• Pure PTB1 and PTB2 polymer, the exciton dissociation under photon illumination is ffi i d i h P3HT

( ) (0)(0)

ph ph

ph

I B II

MFP =

more efficient compared with pure P3HT.

• The bonding energy of charge-transfer exciton at the interface of PTB1 (or PTB2) and PCBM is weaker than the bonding energy in P3HT and PCBM system.

• Polymer PTB1 shows less recombination of dissociated electrons and holes compared with polymer PTB2.

ITO/P l PCBM/Al •The permittivity or dielectric constant of

8. Larger dielectric constant-Impedance Studies

150

200 P3HT PTB1PTB2

ITO/Polymer:PCBM/Al

nce

( 2) ( 1) ( 3 )PTB PTB P HT

•The permittivity or dielectric constant of pure PTB2, PTB1, and P3HT have the relationship

50

100

PTB2

apac

itan ( 2) ( 1) ( 3 )r r rPTB PTB P HT

0 20 40 60 80 100 1200

C

Light intensity (mw/cm2)

•The effective permittivity or dielectric constant of the three blend systems also keep the relationshipLight intensity (mw/cm )

( 2 : ) ( 1: ) ( 3 : )eff eff effPTB PCBM PTB PCBM P HT PCBM

p p

• Strong local dielectric interaction lead to more efficient dissociation and less geminate recombination.

New polymers with high solar conversion efficiency

0.8

1.0 PTB1 PTB2 PTB3 PTB4 PTB5A

BS

b

0 2

0.4

0.6 PTB6

Nor

mai

lized

A

400 600 8000.0

0.2N

Wavelength (nm)

4 PTB1 PTB2PTB3cm

2 )Current – voltage characteristics of polymer/PC61BM solar cells

4

m2 )

a PTB3 PTB4PTB5

60b

-8

-4

0 PTB3 PTB4 PTB5 PTB6

t den

sity

(mA

/c

-8

-4

0

dens

ity (m

A/c

m PTB5

20

30

40

50

EQ

E (%

)

-0.4 -0.2 0.0 0.2 0.4 0.6 0.8

-12

Cur

rent

Voltage (V)-0.4 -0.2 0.0 0.2 0.4 0.6 0.8

-12

Cur

rent

d

Voltage (V)400 500 600 700 800

0

10

Wavelength (nm)

Polymers Voc (V) Jsc (mA/cm2) FF (%) PCE (%)PTB1 0 58 12 5 65 4 4 76

Note: a. Devices prepared

g ( )

Table 2. Characteristic Properties of Polymer Solar Cells.

PTB1 0.58 12.5 65.4 4.76PTB2 0.60 12.8 66.3 5.10PTB3 0.74 13.1 56.8 5.53PTB4 0 76 9 20 44 5 3 10

p pfrom mixed solvents dichlorobenzene/diiodooctance (97/3, v/v)PTB4 0.76 9..20 44.5 3.10

PTB5 0.68 10.3 43.1 3.02PTB6 0.62 7.74 47.0 2.26PTB3a 0 72 13 9 58 5 5 85

v/v).

b. Value after spectral correction.

PTB3a 0.72 13.9 58.5 5.85PTB4a 0.74 13.0 61.4 5.90(6.10b)PTB5 a 0.66 10.7 58.0 4.10

(under AM 1.5 condition (100mW/cm2)

TEM images of polymer/PC61BM blend films:

a. PTB1b. PTB2c PTB3c. PTB3d. PTB4e. PTB5f. PTB6prepared from mixedsolvents dichlorobenzene/diiodooctance (97/3 v/v):diiodooctance (97/3, v/v): g. PTB3h. PTB4i. PTB5

CAFM images (right) of polymer/PC61BM blend films

PTB2 PTB6

The white regions in CAFM (low current) correspond to the PCBM-rich areas, consistent with hole current images and topography images.

24

consistent with hole current images and topography images.

PTB4/PC71BM Solar Cells

70

80

PC71BM -4

-2

0

/cm

2 )

40

50

60 PC61BM

E (%

)

-10

-8

-6

4

ensi

ty (m

A/

10

20

30

EQ

E

-16

-14

-12

10

Cur

rent

De

300 400 500 600 700 800 9000

10

Wavelength (nm)

0.0 0.2 0.4 0.6 0.8-16C

VoltageCurrent – voltage plot of PTB4/PC71BM

l llg ( )

solar cells

Voc (V) Jsc (mA/cm2) FF (%) PCE (%)

PTB4/PC61BM 0.74 13.0 61.4 5.9 (6.1a)

a. Value after spectral correction

PTB4/PC71BM 0.70 14.8 64.6 6.7(7.1a)

PTB7/PC71BM Solar CellsORa 70

S

S

OR

S

n

a

50

60

70

S

ORS

ROOC

nF

R = 2-ethylhexyl PTB7 30

40

EQE

0

10

20

0.8

1.0

1.2 PTB7 PTB7/PC71BM

zed

AB

S

300 400 500 600 700 800 9000

Wavelength (nm)400 500 600 700 800

0.0

0.2

0.4

0.6

Nor

mal

iz

Wavelength (nm)

-8

-6

-4

-2

0

(mA

/cm

2 )

Voc(V)

Jsc(mA/cm2)

FF(%)

PCE(%)

Jsc (Cal.)(mA/cm2)

Error (%)

a. DCB 0.74 13.95 60.25 6.22

b DCB+DIO 0 74 14 09 68 85 7 18 13 99 0 74

g ( )

0.0 0.2 0.4 0.6 0.8

-14

-12

-10Jsc

(

Voc (V)

b. DCB+DIO 0.74 14.09 68.85 7.18 13.99 0.74

c. CB 0.76 10.20 50.52 3.92d. CB+DIO 0.74 14.50 68.97 7.40 14.16 2.34

The Best Solar cell Systems:PTB7/PC71BM

-6

-4

-2

0

cm2 )

-14

-12

-10

-8

-6

Jsc

(mA

/c

0.0 0.2 0.4 0.6 0.8Voc (V)

Voc (V) Jsc (mA/cm2) FF (%) PCE (%)

PTB7/PC71BM 0.74 14.0 68.6 7.4

Polymer Solar Cells Efficiency Chart

O

O

n

MDMO-PPV

NS

N

SS

R R

nR = 2-ethylhexyl

S n

PCPDTBT

Effects of fluorination on physical properties.Synthesis of monomers

S

S

OR1

S

S

OR1Br

Br BrS

S

OR1BrBr2

CHCl3

1. BuLi

2. MeOH

1. BuLi

2. PhSO2NF

Synthesis of monomers

OR1 OR1Br OR1

Br

S

OR1FS

OR1F

Br BrS

OR1F

M S S MBr2 1. BuLi

S

OR1F

S

OR1F

Br BrS

OR1F

Me3Sn SnMe3CHCl3 2. SnMe3Cl

Polymerization

S

S

BrBr

S

S

OR1X2

Me3Sn SnMe3

Pd(PPh3)4

DMF/Toluene+

S*

S

S

OR1X2

*n

X1

OR2O OR1

X2

DMF/TolueneS

X1

OR2O

S

OR1X2

PTBF0 : X1 = H, X2 = H, R1 = n-octyl, R2 = 2-ethylhexyl PTBF2 : X1 = H, X2 = F, R1 = 2-ethylhexyl, R2 = 2-ethylhexyl

PTBF1 : X1 = F, X2 = H, R1 = 2-ethylhexyl, R2 = 2-ethylhexyl PTBF3 : X1 = F, X2 = F, R1 = 2-ethylhexyl, R2 = 2-ethylhexyl

1.0

S

PTBF0 PTBF1

Physical Properties of fluorinated polymers

3 5

-3.0

3 59

-3.22 -3.31

3 60

0 4

0.6

0.8

mal

ized

AB

S

PTBF2 PTBF3

-4.5

-4.0

-3.5

eV

-3.59-3.60

400 500 600 700 800

0.2

0.4

Nor

m

-5.5

-5.0

PTBF0 PTBF2 PTBF3PTBF

-5.15-4.94

-5.41 -5.48

Wavelength (nm)

Table 2. Molecular weights and absorption properties of the polymers

1

Polymer Mw

(Kg/mol)

PDI max (nm) onset (nm) Egopt (ev)

p ope es o e po y e s

(Kg/mol)

PTBF0 23.2 1.38 683, 630 780 1.59

PTBF1 97.5 2.10 671, 628 737 1.68

PTBF2 26.7 2.38 670, 611 709 1.75

PTBF3 78.4 2.61 670, 613 717 1.73

Calculated values of dihedral angles and energy levels of polymers at the B3LYP/6-31G* level of theory

Polymer Dihedral angle

(degree)

LUMO (eV) HOMO (eV) Eg (eV)

PTBF0 163 3 2 67 4 88 2 21PTBF0 163.3 -2.67 -4.88 2.21

PTBF1 161.0 -2.73 -4.99 2.26

PTBF2 179.5 -2.79 -4.89 2.10

PTBF3 179.8 -2.87 -4.98 2.11

1500

2000 PTBF0 PTBF1 PTBF2 polymer d1 (Å) d2 (Å)

The d-spacing values of the polymers.X-ray diffraction

500

1000

Cou

nts PTBF3

p y ( ) ( )

PTBF0 3.8 31

PTBF1 4.0 28

10 20 30 40 50

0

2 Theta (degree)

PTBF2

PTBF3

4.0

4 0

29

28

Pol merPolymer/PC71BM

Sol entJsc

Voc (V) FF PCE(%)

Solar cell characteristics and TEM images of composites

Polymer(w/w ratio)

Solvent(mA/cm2)

Voc (V) FF PCE(%)

PTBF0 1:1 DCB 14.1 0.58 62.4 5.1

PTBF1 1:1.5 DCB 14.0 0.74 60.3 6.2

PTBF1 1:1.5 DCB/DIO 14.1 0.74 68.9 7.2

PTBF2 1:1.5 DCB 11.0 0.68 43.4 3.2

PTBF2 1:1.5 DCB/DIO 11.1 0.68 42.2 3.2

PTBF3 1:1.5 DCB 9.1 0.75 39.4 2.7

PTBF3 1:1 5 DCB/DIO 8 8 0 68 39 0 2 3PTBF3 1:1.5 DCB/DIO 8.8 0.68 39.0 2.3

-4

-2

0

/cm

2 )

PTBF0 PTBF1 PTBF2

ab

12

-10

-8

-6

Cur

rent

(mA

/

PTBF3b

-0.2 0.0 0.2 0.4 0.6 0.8

-14

-12C

Voltage (V) PTBF0 (a), PTBF1 (b), PTBF2 (c), PTBF3 (d). Scale bar = 200μm.

c d

T=0 T=10 sec T=20 sec

FT-IR of PTBF3 film on KBr as a function of time of irradiation.

Absorption spectra of PTBF3 film recorded as a function of irradiation time under air.

0.3

0.4

ion

T=30 sec T=40 sec T=50 sec T=60 sec T=70 sec T=80 sec T=95 secT=110 sec

44

48

ance

T= 0 T= 30 min T=1 hr 30 min T=4 hr T=7 hr

0.1

0.2

Abs

orpt

T 110 sec T=130 sec T=150 sec T=180 sec T=220 sec T=8 min T=14 min T=1 hrT=2hr 15min

40

Tran

smitt

a

400 500 600 700 8000.0

Wavelength (nm)

T=2hr 15min T=3hr 30min T=20 hr

1800 1500 1200 900 60036

Wave numbers (cm-1)Decrease in the optical density (max) of

80

100

44

48

ance

T= 0

polymer films.

20

40

60

OD

(%)

PTBF0 PTBF1

36

40

Tran

smitt

a T 0 T= 30 min T=1 hr 30 min T=4 hr T=7 hr

0 30 60 90 120 150 1800

20

Time (Sec)

PTBF2 PTBF3 3900 3600 3300 3000 2700 2400 2100

Wave numbers (cm-1)

Negative charges on the atom position A and B

Optical density (%) of PTBF3 (a) and PTBF1 (b) absorption spectra in three diff t t f ti f l d

Position PTBF0 PTBF1 PTBF2 PTBF3

90

100 TolueneToluene with DABCO

different systems as a function of elapsed photolysis time.

aA ( ) -0.209 -0.214 -0.217 -0.221

B ( ) -0.239 -0.234 -0.250 -0.24960

70

80

90

D (%

)

Toluene with DABCO Toluene-d8

OCH3X20 2 4 6 8 10 12

30

40

50OD

S

SX1

*

H3CO

S

S

OCH3

2

X2

*3

0 2 4 6 8 10 12Time (sec)

90

100 Toluene Toluene with DABCO Toluene-d8

b-4.0

-3.5

-3.0

V

-3.59

-3.22 -3.31

-3.60

O3CO

PTBF0 : X1 = H, X2 = H

PTBF1 : X1 = F, X2 = H

PTBF2 : X = H X = F60

70

80

OD

(%)

-5 5

-5.0

-4.5

eV

-5.15-4.94

PTBF2 : X1 = H, X2 = F

PTBF3 : X1 = F, X2 = F

0 20 40 60 80 100 120 140 160

40

50

Time (min)

-5.5

PTBF0 PTBF2PTBF3PTBF1

-5.41 -5.48

Theoretical Maximum Efficiency Based on Energetics

Eox/onset (V) HOMO (eV)a onset (nm) max (nm)b Band gap (eV)c

0.63 -5.34 735,834 <1.,4 eV

0.5

0.6

0.7

0.2

0.3

0.4

abs

(a.u

.)

400 500 600 700 800

0.1

Wave length (nm)

Power conversion efficiency AM 1.5 (%)S

OO PCBM

Dennler et. al. Adv. Mater. 2009, 21, 1–16

S

S*S *

F F0.78 -1.81 0.61 42.86

Voc Jsc PCE max FF

Summary1. Donor-acceptor diblock co-oligomers exhibit rectification effect.

2. Faster rate in charge separation than in charge recombination was observed. However, to achieve high the photovoltaic effect, more structural designs and extensive synthesis of new materials are needed.

3. Low bandgap polymers are needed to efficiently harvest solar energy. A3. Low bandgap polymers are needed to efficiently harvest solar energy. A judicial selection in bandgap is needed to achieve maximized solar conversion. An optimized band-gap exists as shown by the copolymer system.

4 Hi h l l i ht t b t hi hi h l i4. High molecular weight seems to be necessary to achieve high solar conversion efficiency.

5. Overall, physical properties in a new polymer must be synergistically balanced and , p y p p p y y g yoptimized in order to achieve high efficiency.

6. Photochemical stabilities of the polymeric materials are major concerns that need to accumulate datathat need to accumulate data.

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Acknowledgements:

Yongye Liang Dr. Danqing FengHae Jun Son Dr. Xianshang XiaoT X D F H

Molecular Electronics

Man-Kit NgTao Xu Dr. Feng HeBrigett Carsten Dr. Jiangbin XiaZhou Wang Dr. Wei WangClaire Ray Dr. Autrean GasinierJ B bitt D J B ll k

Hengbin Wang

Jiang Ping

Gustove MoralesJoe Babitto Dr. Joe Bullock

Professor Lin Chen (ANL/NW)Dr. Jianchang Guo (ANL/UC)D J di S k

Gustove Morales

Shengwen Yuan

Yungu LeeDr. Jodi Szarko

Dr. Gang Li (Solarmer)D Y W (S l )

Dr. Hau Wang (Argonn)Dr. P. Thiyagarajan, Dr. K. C. Littrell

Dr. Yue Wu (Solarmer)

NSF, DOE, AFOSR, UC-NSF-MRSECSolarmer Energy Inc., Intel

Dr. V. S. UrbanDr. Binhua Lin

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