Powered Paint: Nanotech Solar Ink Brian A. Korgel Department of - - PDF document

▶
powered paint nanotech solar ink
SMART_READER_LITE
LIVE PREVIEW

Powered Paint: Nanotech Solar Ink Brian A. Korgel Department of - - PDF document

Sep 16, 2023 344 likes •753 views

8/26/2014 Powered Paint: Nanotech Solar Ink Brian A. Korgel Department of Chemical Engineering, Texas Materials Institute, Center for Nano- and Molecular Science and Technology The University of Texas at Austin korgel@che.utexas.edu

slide-1
SLIDE 1

8/26/2014 1

Powered Paint: Nanotech Solar Ink

Brian A. Korgel

Department of Chemical Engineering, Texas Materials Institute, Center for Nano- and Molecular Science and Technology The University of Texas at Austin korgel@che.utexas.edu

“Disruptive Solar”

  • Sustainable power competitive with fossil

fuels (high efficiency & low cost)

  • Portable light-weight power (efficiency is not

necessarily the primary concern)

  • “Multipurpose solar”—

examples: protective coatings & solar power fabrics & solar camouflage coatings & solar architectural/design & solar

slide-2
SLIDE 2

8/26/2014 2

Change the way solar cells are made

Print like newspaper Photovoltaic Paints…? Slow, high temperature vacuum processes

To Lower the Cost of Solar Energy… Brittle and heavy Light and flexible

Change the way solar cells are made

To Lower the Cost of Solar Energy…

slide-3
SLIDE 3

8/26/2014 3

This is the basic design of every solar cell A Photovoltaic Device:

Photons (Light)

e- h+

p-type semiconductor n-type semiconductor metal metal support

Approach: Create a solvent-based ink that can be deposited under ambient conditions to obtain inorganic films for photovoltaic devices

Target processability of organics (moderate processing conditions; roll-to-roll high throughput; flexible lightweight substrates) with the stability of inorganic compounds.

slide-4
SLIDE 4

8/26/2014 4

Are nanocrystal PVs a viable alternative to organic PVs? 3% efficiency Sintered at high temp CdSe/CdTe…Cd-based

The Technology Challenge: There is a trade-off between cost and efficiency

slide-5
SLIDE 5

8/26/2014 5

Copper indium gallium diselenide: CIGS

Single junction vapor-deposited CIGS cells have reached >20% PCE; highly tolerant to grain boundaries & composition fluctuations

Chalcopyrite phase:

Isostructural with zinc blende with ordering of Cu and In atoms in the Se sublattice Se Cu In

“Conventional” CIGS are made by vapor deposition of Cu,In,Ga layers followed by high temperature (>500oC) annealing under Se vapor

CIGS layer n-type semiconductor Metal Metal Glass or plastic support

slide-6
SLIDE 6

8/26/2014 6

Nanocrystal ink n-type semiconductor Metal Metal Glass or plastic support Glass Mo CuInSe2 nanocrystals ZnO CdS

Synthesis

Question in 2006: Is it even possible to combine three or four elements in a flask and obtain the desired composition and phase?

slide-7
SLIDE 7

8/26/2014 7

Approach to CIGS synthesis

  • In Sept. 2006, there was no known way to synthesize

CIGS nanocrystals.

  • There were methods for CuInS

2 nanocrystals

reported, but these gave very low yields of material.

  • We knew how to make copper sulfide nanocrystals,

so we started there [Ghezelbash, Korgel, Langmuir, 2005]

  • We first synthesized CuInS

2 nanocrystals, then

extended that to CuInSe2 nanocrystals

  • -dichlorobenzene, 180oC
  • leylamine/octenoic acid

CuS nanodisks

Made by Andrew Heitsch Cu(acac)2 + S CuS nanodisks

  • A. Ghezelbash, B. A. Korgel, “Nickel Sulfide and Copper Sulfide Nanocrystal Synthesis and Polymorphism,” Langmuir, 21 (2005)

9451-9456.

slide-8
SLIDE 8

8/26/2014 8

  • -dichlorobenzene, 180oC
  • leylamine

CuInS2 nanocrystals

Cu(acac)2 + In(acac)3 + 2S CuInS2 nanocrystals

CuInS2 nanocrystals

XRD pattern matches tetragonal (chalcopyrite) CuInS2

20 25 30 35 40 45 50 55 60 65 70 75 80

(211)

EDS: Cu(L): 29% In(L): 25% Se(L): 46%

(316) (322) (400) (312) (204) (220) (200) (112)

Intensity (arb. units) 2

slide-9
SLIDE 9

8/26/2014 9

  • leylamine, 240oC

CuInSe2 nanocrystals

CuCl + InCl3 + 2Se CuInSe2 nanocrystals

100 nm

CISe

~15 nm

Oleylamine ligands

CIGS Nanocrystal Synthesis

N2

Tributylphosphine selenide

Oleylamine, CuCl, InCl3

N2

OR

Oleylamine, CuCl, InCl3/GaCl3, Se Heat to 180°C Inject TBP:Se React at 240°C for 15 min Heat to 260°C for 30 min

18

Panthani, M.G.; Akhavan, V.; Goodfellow, B.; Schmidtke, J.P.; Dunn, L.; Dodabalapur, A.; Barbara, P.F.; Korgel, B.A., JACS 2008 130(49), 16770‐16777.

slide-10
SLIDE 10

8/26/2014 10

19

15 – 20 nm crystalline CuInSe2 nanocrystals

N2

TC

  • leylamine, 240oC

CuCl + InCl3 + 2Se CuInSe2 nanocrystals

A nanocrystal ink:

Chemical synthesis of CIGS nanocrystals

CISe Organic capping ligands

~15 nm

  • M. G. Panthani, V. Akhavan, B. Goodfellow, J. P. Schmidtke, L. Dunn, A. Dodabalapur,
  • P. F. Barbara, B. A. Korgel, “Synthesis of CuInS2, CuInSe2 and Cu(InxGa1-x)Se2 (CIGS)

Nanocrystal ‘Inks’ for Printable Photovoltaics,” J. Am. Chem. Soc. 130 (2008) 16770-16777.

slide-11
SLIDE 11

8/26/2014 11

  • leylamine, 240oC

CuCl + InCl3 + 2Se CuInSe2 nanocrystals

Chemical synthesis of CIGS nanocrystals

Dariya Reid (undergraduate chemical engineer)

  • leylamine, 240oC

CuCl + InCl3 + 2Se CuInSe2 nanocrystals

CISe Organic capping ligands

~15 nm

slide-12
SLIDE 12

8/26/2014 12

  • 1. Deposit metal

foil onto a flexible substrate

  • 2. Solution-deposit

nanocrystals

  • 3. Deposit heterojunction

partner layers (CdS/ZnO)

  • 4. Pattern metal

collection grid

Nanocrystal PV Device Fabrication

Nanocrystal Film Formation

For the solar cell, need uniform films of nanocrystals.

slide-13
SLIDE 13

8/26/2014 13 Efficiency 0.341% Voc 329 mV Jsc 3.26 mA/cm2 Fill Factor 0.318

  • Standard Cell

Glass Mo CuInSe2 nanocrystals ZnO CdS Efficiency 0.341% Voc 329 mV Jsc 3.26 mA/cm2 Fill Factor 0.318

  • Standard Cell

Glass Mo CuInSe2 nanocrystals ZnO CdS Mo work function is ~4.2 eV, resulting in a Schottky barrier at the Mo/CIS interface

slide-14
SLIDE 14

8/26/2014 14 Project conception (Sept., 2006)

3.1%

Korgel group milestone chart for CIGS Nanocrystal PVs

Nanocrystal Film Formation

For the solar cell, need uniform films of nanocrystals.

slide-15
SLIDE 15

8/26/2014 15

  • 40
  • 20

20 40 60 80 100 120 140 160

  • 1.5
  • 1
  • 0.5

0.5 1 1.5

Voltage (V) Current Density (mA/cm2)

DARK LIGHT Jsc: -16.287 mA/cm

2

Voc: 0.412 V FF: 0.456 PCE: 3.063 %

CIS Nanocrystal PV device

  • V. A. Akhavan, M. G. Panthani, B. W. Goodfellow, D. K. Reid, B. A. Korgel, “Thickness-

limited performance of CuInSe2 nanocrystal photovoltaic devices,” Optics Express, 18 (2010) A411-A420.

Efficiency

  • f 3.1%

Flexible CIGS PVs

slide-16
SLIDE 16

8/26/2014 16 Efficiency of 2% on plastic CIGS Nanocrystal Solar Cell Fabricated on Ultra-Light Ni-coated PET

Estimated Weight 31.4”x 61.4” Panel Standard Si: 33 lbs (15 kg) CIGS on PET/Ni: 0.5 lbs (.25 kg)

slide-17
SLIDE 17

8/26/2014 17 Reduce grain boundaries by synthesizing nanowires?

slide-18
SLIDE 18

8/26/2014 18

Bi-seeded CuInSe2 Nanowires by SLS

20 40 60 80 Chalcopyrite CuInSe2

Intensity (arb. units)

2

XRD

10 nm

HRTEM

Perpendicular to (112) planes

EDS analysis: Cu1.0In0.6Se2.0

NW Characterization

slide-19
SLIDE 19

8/26/2014 19

Wurtzite Phase CuInSe2 Nanowires

twinning

  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3

  • 0.6
  • 0.4
  • 0.2

0.0 0.2 0.4 0.6 0.8 1.0

500 750 1000 1250

0.1 0.3 0.5 0.7 0.9

Light

Current Density (mA/cm

2)

Potential (V)

VOC = 186 mV JSC = 0.248 mA/cm2 FF = 0.295

 = 0.014%

Dark

Band Edge ~1 eV Absorbance

Wavelength (nm)

Current voltage characteristics of a CuInSe2 nanowire PV device. Inset: UV-vis-NIR absorbance spectrum of CuInSe2 nanowires dispersed in toluene. Proof of concept

slide-20
SLIDE 20

8/26/2014 20

CIS Nanowires PV Device Absorber Film With CdS An idealized device structure Device composed of a nanowire mat

How to achieve power conversion efficiencies of 10-20%? Accomplished to date:

  • Solar inks can be chemically synthesized
  • Solar cells can be fabricated with solar inks
  • Solar cells can be fabricated with solar inks
  • n light-weight flexible substrates
slide-21
SLIDE 21

8/26/2014 21

Photons (Light)

e- h+

Extracting the photogenerated electrons and holes efficiently is currently the biggest challenge

The highest efficiency devices have very thin nanocrystal layers that do not absorb all of the light

~200 nm thick layer of nanocrystals on glass disc

slide-22
SLIDE 22

8/26/2014 22

Thicker nanocrystal layers absorb more light, but lead to less efficient devices

  • V. A. Akhavan, M. G. Panthani, B. W. Goodfellow, D. K. Reid, B. A. Korgel, “Thickness-limited

performance of CuInSe2 nanocrystal photovoltaic devices,” Optics Express, 18 (2010) A411-A420.

120 nm 250 nm 400 nm

Thicker nanocrystal layers absorb more light, but are less efficient

  • V. A. Akhavan, M. G. Panthani, B. W. Goodfellow, D. K. Reid, B. A. Korgel, “Thickness-limited

performance of CuInSe2 nanocrystal photovoltaic devices,” Optics Express, 18 (2010) A411-A420.

120 nm 250 nm 400 nm

CISe Organic capping ligands

~15 nm

Oleylamine ligands

slide-23
SLIDE 23

8/26/2014 23

45

CIS 15 nm

  • Nanocrystals are coated with oleylamine
  • Long chain hydrocarbon impedes carriertransport
  • Improve charge transport by replacing oleylamine
  • leylamine

What to do with oleylamine?

  • Anneal?

– Leaves surface unpassivated

  • Ligand exchange

– Several attempts, but none have been successful

  • Larger particles

– Less boundaries for carriers

  • Synthesize with shorter ligand

– Shorter ligands are volatile, particles unstable

46

CIS CIS

slide-24
SLIDE 24

8/26/2014 24

Improving transport?

Pg 48

Selenization of CIGS Nanocrystals for High Efficiency PV’s

Boat with Se Pellets CIGS Film

As Deposited

Mo CIGS MoSe2 Mo CIGS

Selenized

1 μm 1 μm

slide-25
SLIDE 25

8/26/2014 25

200 nm

CuInSe2 nanocrystal film without annealing

10 μm

200 nm

CuInSe2 nanocrystal film heated to 550oC under nitrogen (no Se vapor)—no sintering observed

slide-26
SLIDE 26

8/26/2014 26

10 μm

500 nm

CuInSe2 nanocrystal film annealed at 550oC under Se atmosphere—sintering and grain growth

Selenization: Heating nanocrystal film to 525oC under Se

vapor atmosphere

Sintering requires high temperature (>450C) and Se vapor

slide-27
SLIDE 27

8/26/2014 27

7.1% efficiency

Pg 54

Photonic Curing of CIS and CdTe Nanocrystal Films CIS CdTe

500 nm 500 nm

slide-28
SLIDE 28

8/26/2014 28

Temperature profile during photonic curing process 8.1 ± 2.1 nm in diameter CuInSe2

slide-29
SLIDE 29

8/26/2014 29

slide-30
SLIDE 30

8/26/2014 30

2.2 J/cm2 3.0 J/cm2 No pulse sintered Not sintered Internal quantum efficiency >100% under white light bias As-deposited After photonic curing IPCE measured under white light bias

slide-31
SLIDE 31

8/26/2014 31

Multiple Exciton Solar Cells of CuInSe2 Achieving External Quantum Efficiency > 100%

# of electron/hole extracted Incident photon

( )

slide-32
SLIDE 32

8/26/2014 32

Thermal Gravimetric Analysis (TGA) Amount of ligand in the film X-ray diffraction Peak narrowing indicates sintering No sintering in the film with MEG As-deposited 2.2 J/cm2

slide-33
SLIDE 33

8/26/2014 33

Check optically that MEG exists in the material

slide-34
SLIDE 34

8/26/2014 34

Transient absorption spectra There is a bleach at the band edge Confirmation of MEG in CuInSe2 nanocrystal films Stolle, et al. J. Phys. Chem. Lett. 2014.

slide-35
SLIDE 35

8/26/2014 35

Three CuInSe2 quantum dot sizes studied by TAS TAS: 800 nm pump (3 dif sizes)

slide-36
SLIDE 36

8/26/2014 36

Very short time TAS data (carrier cooling rates) TAS kinetics as a function of nanocrystal size

slide-37
SLIDE 37

8/26/2014 37

Table 1: MEG efficiency, MEG threshold, and bulk band gap for a variety of semiconductor nanocrystals found in the literature. Reported samples were stirred to avoid anomalous effects due to photocharging.14,23 Semiconductor Nanocrystal MEG Efficiency (%) MEG Threshold (hν/Eg) Bulk Band Gap (eV) Reference CuInSe2 36 2.4 1.0

  • PbS

40 3 0.5

24

PbSe 40 3 0.37

23

InAs 35 2 0.36

25

InP 30 2.1 1.27

7

CdSe/CdTe 53 2.7 0.91

26

1.36 excitons are generated at a pump energy of 3.4*optical gap

Image from Semonin, Beard, Nozik, SPIE Newsroom (2012)

Shockley-Queisser Limit: 34% efficiency

slide-38
SLIDE 38

8/26/2014 38

First report of EQE>100% in a functioning device

Multiple Exciton Generation and Extraction from a Nanocrystal Photovoltaic Device

Surface traps currently limit device efficiency; Low open circuit voltage

slide-39
SLIDE 39

8/26/2014 39 Next step: Try to recover Voc by passivating surface traps

Next: Passivate the traps?

(a printed PV with 10% efficiency)

Nozik, Beard, et al. (2011)

Printed Nanocrystal-Based Photovoltaics

  • Nanocrystal inks: MEG occurs in CuInSe2 nanocrystals
  • Multiexciton extraction in PV devices appears to be

relatively viable

  • Is it possible to create multiexciton solar cells with high

device efficiency?

Financial support : Robert A. Welch Foundation (F-1464), the Air Force Research Laboratory (FA-8650-07-2-5061) and the NSF Industry/University Cooperative Research Center on Next Generation Photovoltaics (IIP-1134849).

slide-40
SLIDE 40

8/26/2014 40

Special Acknowledgement to: Vahid Akhavan Brian Goodfellow Matt Panthani Danny Hellebusch Dariya Reid Jackson Stolle Taylor Harvey Key undergraduate researchers 1st gen PV students Next gen PV students

Financial support : Robert A. Welch Foundation (F-1464), the Air Force Research Laboratory (FA-8650-07-2-5061) and the NSF Industry/University Cooperative Research Center on Next Generation Photovoltaics (IIP-1134849).