Organic-Inorganic Hybrid Materials for IR-Photodetection and - - PowerPoint PPT Presentation

7th Korea-US Nano Forum Seoul, April 5-6, 2010

Organic-Inorganic Hybrid Materials for IR-Photodetection and Photovoltaics IR-Photodetection and Photovoltaics

20nm

Kwang-Sup Lee

D f Ad d M i l Department of Advanced Materials, Hannam University, Daejeon 305-811, Korea

Contents I d i

• Introduction

Quantum Dot based Hybrids

• Quantum Dot-based Hybrids

* Enhancing the Photocurrent Density * Photopatternable Quantum Dots * Photopatternable Quantum Dots

• Low Bandgap Polymers

Low Bandgap Polymers

• C60 Derivatives
• Summary

IR Photodetection

Increase detectivity Increase number of applications

Medical W h Medical (Thermal Imaging) Weather Military Astronomy:

Infrared Image of the Milky Way y y

Solar Spectrum

(Nanocrystal Quantum Dots)

Pb (Lead) Se (Selenium) Se (Selenium)

PbSe (for IR) CdSe, InP, InP-CdS core-shell (for visible) Z S CdS (f UV)

• Semiconducting characteristics
• Excellent quantum size effects

ZnSe, CdS (for UV)

• Excellent quantum size effects
• Efficient excitonic generation
• Tunable absorption and emission in

Tunable absorption and emission in the UV to IR

Tuning of Spectral Response by Choosing Quantum Dots

Absorption Luminescence

λ

ZnSe

Broadband Absorber

CdSe, InP

λ

CdSe, InP Quantum Dots PbSe

λ

CdSe QD

20n m

Preparation of PbSe Nanocrystals

Ar precursors Thermocouple

• rganic capping to
• rganic capping to

enable dispersion enable dispersion

Heating mantle mantle Stir plate reactants + solvent

Semiconductor quantum dot core-shell/bipods/tripods/ tetrapods

(PbO + Oleic acid in tri n octylamine solvent)+ TOP Se or TBP Se (PbO + Oleic acid in tri-n-octylamine solvent)+ TOP-Se or TBP-Se Comments: Size and shape control + Surface functionalization of the ti l i t t t particles are very important steps.

Comparative Environmental Stabilities of IR QDs and IR Organic Dyes IR Organic Dyes

Excitation - 720 nm Emission - 830 nm. Normal laboratory environmental storage environmental storage conditions.

Hybrid Materials for IR Photodetection QD / Pentacene / PVK Polymeric Nanocomposite Polymeric Nanocomposite

Pentacene Pentacene

Synthetic Route for Pentacene Precursor

O

Ali Afzali, et.al, J. Am. Chem. Soc. 2002, 124, 8812.

H3C C N S O

+

N-sulfinylacetamide Pentacene

O

y Pentacene CH3ReO3

S N O

CHCl3

Pentacene precursor

“Soluble in CHCl3, CH2Cl2

”

Prepared by the Diels-Alder reaction between pentacene & N-sulfinylamide in the presence of a catalytic amount of methyltrioxorhenium,

Device Processing for IR Photodetector

N O

n

S O

N n

Pentacene precursor PbSe nanoparticle PVK

PVK-Pentacene precursor-PbSe Film Baked in vacuum oven at 240 oC Measured Photoconductivity

Film Composition: PVK 30 wt%, Pentacene precursor 30 wt%, PbSe 40 wt%

Evaluation of Photoconductivity

sample sample ITO ITO

light light

ITO ITO electrode electrode focused focused collimated collimated

R HV V

Typical I-V Curve

Keithley Keithley source meter source meter

Photocurrent density as a function of applied voltage in devices with the same proportion of PVK: pentacene (3:1) but various amounts of PbSe same proportion of PVK: pentacene (3:1) but various amounts of PbSe nanocrystals as indicated in the legend.

• Appl. Phys. Lett., 87, 051109 (2006) / US Patent 0128021 A1, 2008

Photocurrent density as a function of applied bias (1340 nm) in different devices with varying proportions of PVK and pentacene

The photocurrent increases significantly as the amount of pentacene in the composite increases The photocurrent increases significantly as the amount of pentacene in the composite increases. The best performance was extracted in devices with equal amounts of PVK and pentacene (having 25 wt % of PbSe QDs). The enhancement in photocurrent, compared to a PVK-PbSe film, is over 8 times.

Comparison of the external quantum efficiency of the composite devices

2 % f S 25 wt % of PbSe

Max EQE: Max EQE: ~ 8% in the IR ~ 8% in the IR

A maximum external quantum efficiency (EQE) of ~8% at an applied device bias of 5 V is achieved in the composite having equal amounts of PVK and pentacene. This is an improvement of eight times over the PVK:PbSe devices under similar experimental improvement of eight times over the PVK:PbSe devices under similar experimental conditions.

QD-Carbon Nanotube / PVK Polymeric Nanocomposite

Carbon Nanotubes Coupled with Quantum Dots

SWCNT PbS QD SWCNT-PbSe QDs

SWCNT-CdSe SWCNT CdS SWCNT-CdS

• J. M. Haremza et al, Nano Lett. 2, 1253 (2002)

SWCNT-CdSe

• S. Banerjee et al, Nano Lett. 2, 195 (2002)
• I. Robel et al,
• Adv. Mater. 17, 2458 (2005)

QD-SWCNT-Polymer Nanocomposites for Photovoltaics Photovoltaics

S A i h hi l AET

QD QD

SH H2N SH NH 2 HS NH 2 HS NH SH H2N

AET

Spacer: Aminoethanethiol: AET

NH 2 HS NH 2 SH NH 2 SH H 2N

COOH ligand exchange COOH COOH SWCNT carboxylation COOH COOH COOH COOH COOH

Dots

A variety of QDs active from UV to IR enables us to access a wide part of the solar spectrum

b

10 nm 10 nm

3 nm

2000 2500 1500

sity (a.u.)

1000

PL intens

500 1000 1100 1200 1300 1400 1500 1600

Wavelength (nm) PL spectra of PbSe QDs (solid line) and SWNT-PbSe (dotted line) in tetracholoethylene colloidal suspensions. The concentration of y p PbSe QDs was the same in both cases.

I-V Characteristics of PbSe QD/PVK and SWNT-PbSe /PVK Device in Dark and under Illumination

R H V V Keithley source meter Keithley source meter

• Adv. Mater., 19, 232-236 (2007) / US Patent 2010-0025662 A1, 2011

ACS “Heart Cut” Research Highlight, 2007

Contents I d i

• Introduction

Quantum Dot based Hybrids

• Quantum Dot-based Hybrids

* Enhancing the Photocurrent Density * Photopatternable Quantum Dots * Photopatternable Quantum Dots

• Low Bandgap Polymers

Low Bandgap Polymers

• C60 Derivatives
• Summary

Surface Functionalization for Photo-Patternable QDs

O O NH O O NH2

hv with H+ catralyst

Chemical Amplification Reaction

D

N H O O S S NH O O S S HN S H N O O S NH O S S NH2 S S NH2 S S S H2N S H2N S S

hv with H+ catralyst Δ

QD

Q D

HN O O HN O O S HN O O NH2 H2N S H2N

S e P b

Nano Lett., 8, 3262(2008)

Photocurrent Measurements of Photopatternable QDs

(a)

4 5 CdTe (t-BOC protected) CdTe (Deprotected) 2 3 rent (nA) ( p ) Dark 1 2 Curr 5 10 15 20 25 30 35 Electric Field (MV/m)

(b)

Current-voltage curves (a) in the dark or with white light (100 mW/cm2) illumination for a film of t-BOC protected and deprotected CdTe nanocrystals (measured at the voltage scan rate is 1 V/s). The channel length is 5 μm. MSM device structure (b) for photoconductivity measurement.

Polymer Nanocomposite Photovoltaics utilizing CdSe QDs Capped with a Thermally Cleavable Solubilizing Ligand

P3HT: CdS i

Al PEDOT

P3HT: CdSe-amine

ITO

1.0 1.5

/cm

2)

0 01 0.1 1

nsity (mA/cm

2)

Solar Cell Device Structure

0.0 0.5

sity (mA/

0.0 0.2 0.4 0.6 0.8 1.0 1E-3 0.01

Current den Voltage (V)

1 0

• 0.5

rent dens

100

• C (photo)

100

• C (dark)

Thermal cleavage of t-BOC

0.0 0.2 0.4 0.6 0.8 1.0

• 1.5
• 1.0

Curr

100 C (dark) 200

• C (photo)

200

• C (dark)

Voltage (V)

• Appl. Phys. Lett., 94, 133302 (2009)

O O Si O O O O Si O O Si O Si O O O Si O O O S S S S

CdSe

11 11 11 11

O O

11

QD 1 UV: 552nm PL: 568nm

3-D Lithographic Microfabrication

♦ Localized photochemistry by TPA process

C i

Polymerized

Collimated Laser Beam

Photocurable film Polymerized region Objective lens Focused beam

Lens

Single-photon polymerization Two-photon polymerization

j

TPA : volume of order λ 3 Lens TPA : volume of order λ

DOF Localized photo- polymerization Width polymerization

Use of longer radiation wavelengths in TPA process is possible to achieve the better Use o

• ge

ad at o wave e gt s p ocess s poss b e to ac eve t e bette penetration depth in the medium

S S S

PV DTT Flu PE

R R N R R R R R R R R R R R R R R R R R R R R R N

S S

S S S N N OC12H25 C12H25O OC12H25 C12H25O

NBu2-DTTPE-NBu2

R R R

Polymers Ceramics

NBu2-DTTPE-NBu2

Metals Metals

CdSe/ZnS Core-Shell

CdSe

Figure (a) shows the photocuring of working acrylate functionalized quantum dots with its layer structure, (b) Shows the synthesis scheme for the acrylate functionalized photopatternable quantum dots.

Photopatterns by Using CdSe/ZnS Core-Shell QDs

Clli t dL B

Polymerized

C

• llim

a ted L a ser B ea m

L

Single-photon polymerization Two-photon polymerization

Photocurable film Polymerized region Objective lens Focused beam

Size distribution of Nanorods: 10 -30 nm

T P A : v

• lu

m e o f o rd er λ3 L en s

D O F L

• ca

lizedp h

• to

W id th L

• ca

lized p h

• to
• p
• ly

m eriza tio n

Polymer Blocking Layer Effect on In2S3/CuInSSe Solar Cell

PEDOT:PSS

• 5

5

2)

• eV

PEDOT:PSS Blocking the back recombination

• 15
• 10
• 5

sity (mA/cm

2

+

• Ec

EF

• 4
• 5
• 3

Au

+

• 25
• 20

Current Dens

InS/CISSe/A

Ev TiO In S CuInS2, CuInSe2

• 6
• 7
• 8

Au

• 0.1

0.0 0.1 0.2 0.3 0.4

• 35
• 30

C Voltage (V)

InS/CISSe/Au InS/CISSe/PEDOT:PSS/Au

TiO2 In2S3 or CuInSSe

V is similar

g ( )

Voc (V)

Jsc(mA/cm2)

FF(%) PCE(%)

Voc is similar Jsc shows significant increase FF is decreased PCE increases due to the Jsc increment

( ) w/o PEDOT:PSS ~0.26 18.4 35.3 1.69 with

PCE increases due to the Jsc increment PEDOT:PSS effectively blocks electrons & transports holes

with PEDOT:PSS ~0.29 33.5 31.9 3.16

electrons & transports holes

Prasad et.al, 2009

Low-Bandgap Conjugated Polymers g p j g y

S S N S N n S n

A

PCPDTBT

n

P3HT

D-A concept Rigiospecific Structure Optical Bandgap: 1.52 eV 1.90 eV

Low Bandgap Conjugated Copolymers: PFTB & PCTB

S S S N S N S

PFTB PCTB

N C8H17 C8H17 S N C8H17 C8H17 N S N S C6H13

m n

R = C8H17: R1 = C6H13 n=0.1, m=0.9

S R R R1 R1 R R

n m

R = C8H17: R1 = C6H13 m=0.9, n=0.1

S S S C6H13

l

n

Abs: λmax PL : λmax Abs: λmax PL : λmax Abs: λmax PL : λmax 521 nm 642 nm 519 nm (with PCBM 1:4) 643 nm (with PCBM 1:4) Abs: λmax PL : λmax 521 nm 642 nm 519 nm (with PCBM 1:4) 642 nm (with PCBM 1:4)

)

Device Jsc Voc FF Solar Efficiency

2

• 2

ent Density (mA/cm2 P3HT

I-V Characteristics and Solar Cell Efficiency

Device (mA/cm2) (V) (%) (%) P3HT/PCBM (1:0.8) 4.234 0.485 49.68 1.02

• 0.1

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

• 4

Curr Voltage (V) P3HT PFTB:PCBM (1:4) )

PFTB/PCBM 3.596 0.881 37.64 1.19 (1:4) PCTB/PCBM 3 782 0 862 38 74 1 26

• 2

Density (mA/cm2)

3.782 0.862 38.74 1.26 (1:4)

• 0.1

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

• 4

P3HT PCTB:PCBM (1:4)

Current Voltage (V)

Development of Efficient NIR Polymers;

Synthesis of the Low bandgap Polymers

N S N N S

N S N

S N

Synthesis of the Low bandgap Polymers

n N S S

PFTTBT

S S N N n N S N S S

n N S S N S N

PFTTBBT S S N S N n

PCPDTBT

PCPDTBBT

0 30 0.35

PFTTBT PCPDTBT

Optical properties of various polymers

0 20 0.25 0.30

(a.u.)

PCPDTBT PFTTBBT PCPDTBBT

Polymer Abs. λmax.

• Opt. band

gap PFTTBT 530 nm 1 98 eV

0 10 0.15 0.20

Absorbance

PFTTBT 530 nm 1.98 eV PCPDTBT 718 nm 1.52 eV

0 00 0.05 0.10

A

PFTTBBT 868 nm 1.19 eV PCPDTBBT 950 nm 0.92 eV

400 600 800 1000 1200 1400 0.00

Wavelength (nm)

Comparison of UV-vis Absorption of Low Bandgap Polymers

B

PCPDTBT (by Heeger’s group)

S S S S Bu3Sn SnBu3 Polymerization (Stille coupling) N S N NSN S N S N N N S Br S

n

S Br PCPDTBBT

B

2

PCPDTBT film PCPDTBT-PCBM blend film PCPDTBBT film

N S N

NSN

ce (a.u.)

PCPDTBBT-PCBM blend film

S S N

n

1

Absorbanc

1100 nm

N S

PCPDTBBT (Our Work)

A

S S S S N N

n

N S N

400 600 800 1000 1200 1400

Wavelenth (nm)

S

37

UV-vis absorption spectra of the PCPDTBT and PCPDTBBT Polymer films and the polymer-PCBM blend films

Contents I d i

• Introduction

Quantum Dot based Hybrids

• Quantum Dot-based Hybrids

* Enhancing the Photocurrent Density * Photopatternable Quantum Dots * Photopatternable Quantum Dots

• Low Bandgap Polymers

Low Bandgap Polymers

• C60 Derivatives
• Summary

C60 Derivatives as Acceptors in Hybrid Bulk Heterojunction Solar Cells

PCBM

(A) (B)

• Fig. (A) The contour plots of the

HOMOs (left side) and the LUMOs, right side) of all investigated dyads. investigated dyads. (B) Electronic energy levels of an isolated dyads. Vertical arrows represent the most probable transitions (with oscillator strength higher than 0 1 Blue red and higher than 0.1. Blue, red, and green arrows corresponds to the LE(F), LE(T), and ICT transitions, respectively.

• Chem. Phys. Lett. 479 , 224 (2009) / Synth. Met. 159, 2539 (2009)

Electron Mobility of New n-Type C60 Derivative (Fu-Hexyl)

Encap glass

N S

S D OSC

getter Al

Inkjet printing (0.5wt% Fu-Hexyl in chlorobenzene)

Fu-Hexyl

n+ Si Gate (SiO2)

Mg

chlorobenzene)

μ=0.028 cm2/V·s (0.0058 cm2/V·s for PCBM) On-off ratio = 1.9 × 105

• Org. Electron, 10, 1028 (2009)

Efficiency of ITO/PEDOT:PSS/P3HT:C60 Derivative/TiOx/Al Solar Cells

2

cm2)

N S

• 4
• 2

sity (mA/c

• 10
• 8
• 6

rrent Dens

P3HT:PCBM P3HT:C60-TH-Hx-3 P3HT:C60-TH-Hx-5

0.0 0.2 0.4 0.6 0.8

• 12

Cur Voltage (V)

P3HT:C60-TH-Hx-5

Fu-Hexyl Compounds Jsc (mA/cm2) V

• c (V)

FF Eff (%) P3HT:PCBM 6.32 0.582 0.65 2.39 P3HT:C60-TH-Hx-3 6.58 0.575 0.64 2.44

Graphic Summary

Profs Paras N Prasad & Alex N Cartwright

Coworkers

• Profs. Paras N. Prasad & Alex N. Cartwright

Institute for Lasers, Photonics and Biophotonics, Univ. at Buffalo, SUNY, Buffalo, USA

• Prof. Andrzej Graja

j j

Polish Academy of Sciences, Poznan, Poland

• Prof. Tae-Dong Kim

Dept of Advanced Materials Hannam Univ Daejeon Korea

• Dept. of Advanced Materials, Hannam Univ., Daejeon, Korea

Funding Agencies g g

KRF KRF KOSEF AOARD / AFOSR Samsung Electronics