Printed Sensors: The Evolution of Materials

Transcription

1 Printed Sensors: The Evolution of Materials Dr Weiping Wu George Daniels Lecturer Department of Electrical and Electronic Engineering City University London

2 Outline Printed sensors Overview of printable sensor materials Conjugated small molecules Conjugated polymers Nano carbon Materials Conclusion and outlook

3 Why Printed Sensors? Inorganic electronics (Si, GaN, SiC, etc) However, there are several major challenges: Expensive, high temperature, vacuum process steps Poor Flexibility Limited to small area

4 From vacuum to solution process Fabrication methods Vacuum deposition High performance High cost Time consuming Solution process Low performance Low cost High efficiency Large area

5 What is the status of Printed Sensors Chemical sensors Temperature sensors Gas sensors Pressure sensors Chemical sensors ph sensors Humidity Sensors Humidity Sensors Heavy metal sensors Biosensor Temperature Sensors Printed Sensors Heavy metal sensors Gas Sensors Pressure sensors Biosensors

6 Printed Sensor Market In 2014, IDTechEx see the market size as follows. This shows the different levels of maturity, revenue and success across the wide variety of options that make up printed, flexible and organic electronics.

7 Outline Printed sensors Overview of printed sensor materials Conjugated small molecules Conjugated polymers Nano carbon Materials Conclusion and outlook

8 Materials for Printed Sensors Materials Processing Microstructure Properties

9 0D 1D 3D K.S. Novoselov, A.K. Geim, S.V. Morozov, et al., Nature 438, 197, 2005

10 Anthracene Tetracene Pentacene Taichi Hayakawa,Yosuke Ishii and Shinji Kawasaki, RSC Adv., 2016, 6,

11 Overview of Organic electronics Organic lighting emitting diode Organic thin film transistor Organic solar cell More Chip, Simple process and Flexible

12 Materials and Inks are the most important! Device usually contains several layers, each layer requires different materials Semiconductor Layer Organic Semiconductor Small molecules (ex: pentacene, oligothiphene) Conjugated polymers (ex: P3HT, PBTTT) Inorganic S.C. (ex: a-si, ZnO, In2O3) Nano Carbon (CNT, graphene, diamond) Insulator Layer Organic Dielectric (ex: Polyimide, PMMA, PVP) Inorganic Dielectric (ex: Al 2 O 3, HfO 2 ) Electrodes Metal or carbon (ex: Au, Ca, CNT, graphene) Conjugated Polymer (ex: PEDOT:PSS) Other Substrate, encapsulation, conection, etc.

13 Conjugated molecules and polymers Weiping Wu, Yunqi Liu, and Daoben Zhu, π-conjugated Molecules with Fused Rings for Organic Field-Effect Transistors: Design, Synthesis and Applications, Chemical Society Reviews, 39 (2010),

14 Outline Printed sensors Overview of printed sensor materials Conjugated small molecules Conjugated polymers Nano carbon Materials Conclusion and outlook

15 cm 2 V -1 s -1 Conjugated small molecules Pentacene is not printable! TIPS-Pentacene 6,13-Bis(triisopropylsilylethynyl) pentacene 6,13-diphenylpentacene Chemical Formula: C 34 H 22 Molecular Weight: Printable! μ= cm 2 /Vs 6,13-di(naphthalen-2-yl)pentacene Chemical Formula: C 42 H 26 Molecular Weight: Printable! μ= cm 2 /Vs

16 a Early printable FET material BTTF (2004) b c μ=0.02 cm 2 /Vs, Ion/Ioff ~ Strong π stacking Similar to CNT and graphene, BTTF has got high mobility but too high conductivity, resulting low on/off ratio and poor stability M. Adam and K. Mu llen, Adv. Mater., 1994, 6, 439 X. K. Gao, W. P. Wu, et. al, Chemical Communications (2006),

17 Tetrathiafulvalene (TTF) Donor Systems for OFETs Compound Mobility (cm 2 V -1 s -1 ) Ion/Ioff n-type

18 Conjugated molecules and polymers TFT materials as an example Structures of p-channel Semiconductors with TFT Characteristics Linear Acenes Linear Heterocyclic Fused Rings Two dimensional Fused Rings Three dimensional Fused Rings 0.001~ 10 cm 2 /Vs mobility (α Si-H μ~1cm 2 /Vs)

19 Outline Printed sensors Overview of printed sensor materials Conjugated small molecules Conjugated polymers Nano carbon Materials Conclusion and outlook

20 Conjugated polymers A common attribute possessed by conjugated materials is that they contain a conjugated carbon "backbone, with a series of alternate single and double carbon bonds.

21 Conjugated Polymers Polyacetylene (PA) Polyaniline (PANI) Polythiophene (PT) Polypyrrole (PPy) Polyfluorenes (PF) Poly(p-phenylene vinylene) (PPV) Poly(3,4-ethylenedioxythiophene) (PEDOT) Poly(p-phenylene) (PPP) Poly(p-phenylene ethynylene) (PPE) 17/01/

22 Conjugated polymers for OFETs Mobility in the range of 10-3 ~ 1 cm 2 V -1 s -1 P-type, n-type and ambipolar conjugated polymers for OFETs Weiping Wu, Yunqi Liu, and Daoben Zhu, π-conjugated Molecules with Fused Rings for Organic Field-Effect Transistors: Design, Synthesis and Applications, Chemical Society Reviews, 39 (2010),

23 PTTV Printable Conjugated polymers AFM images of (a) P3HTV film before thermal annealing, (b) P3HTV film after thermal annealing at 180 o C for 30 min, (c) DH-PTTV film before thermal annealing and (d) DH-PTTV film after thermal annealing at 180 o C for 30 min. (scale: 2 µm 2 µm). He, Y., Wu, W., Zhao, G., Liu, Y. and Li, Y. Poly(3,6-dihexyl-thieno[3,2-b]thiophene vinylene): Synthesis, Field-Effect Transistors, and Photovoltaic Properties. Macromolecules, 41(24), , 2008.

24 Molecular design, Printable Conjugated polymers 1 Introduce building blocks with high ionization potential 2 Attaching strongly electron-withdrawing groups OTPAV-PT PTTV Synthetic Metals 2009, 159, 182 Macromolecules, 2008, 41, 9760 J. Polym. Sci. Pol. Chem., 2009, 47, 5304 PCNT CN N OC 8 H 17 COOC 2 H 5 S S n μ= cm 2 /Vs μ=0.032 cm 2 /Vs S S n C 12 H 25 μ= cm 2 /Vs I DS 1/2 (A) 1/2 a V DS = 100V V G (V) 10-10

25 Printable Polymers HOMO / LUMO (ev) Hole mobility (cm 2 V -1 s -1 ) / Ion/Ioff 5.05 / / 2.96 P1 8.9X10-4 / 10 3 P5 2.17X10-4 / P / / 10 4 P / / P / X10-3 / P / X10-3 / P / X10-4 / P / X10-4 / ~100 25

26 Outline Printed sensors Overview of printed sensor materials Conjugated small molecules Conjugated polymers Nano carbon Materials Conclusion and outlook

27 Carbon Nanomaterials Fullerenes 0D Discovered in 1985 (C60) C60, C70, C84 Films n-type semiconducting Carbon Nanotubes (CNTs) 1D Discovered in 1991 Single and multi-walled Semiconducting or Metallic Graphene 2D Discovered in Nobel Prize Metallic/transparent

28 Graphene for Printed Electronics World s 1 st Ink-jet printed Graphene transistor device Mobility ~95 cm 2 /Vs But, low I on /I off Graphene+PQT-12 ~0.1 cm 2 /Vs Much higher I on /I off 4 x10 5 F. Torrisi, T. Hasan, W. P. Wu, et.al, Inkjet-Printed Graphene Electronics, ACS Nano, 6, , 2012

29 Graphene for Large Area Electronics 10 4 Transmittance (%) Pristine Graphene HNO3 functionalized Graphene/Au Graphene/Ag Sheet Resistance ( /sq) Conductivity (S/m) GO R-GO Graphene Graphene/Ag Conductivity of GO, rgo, graphene by liquid exfoliation and graphene/ag hybrids Transparency (%) PET Graphene Graphene-Ag NP on PET Graphene-Au NP on PET Ag-10nm film on PET Wavelength (nm) Graphene/Au ~200 Ω/ at transparency of 90% Graphene/Ag ~50 Ω/ at transparency of 90% Weiping Wu et. al, Graphene 2012 International Conference, April 2012, Brussels (Belgium).

30 Conclusion and outlook Materials for sensors progressed as an Evolution: Low dimensional carbon systems 0D 1D 2D 3D Fullerenes (C 60 ) Carbon nanotubes Graphene Graphite What can we do next? Soluble, elemental doped Graphene

31 Conclusion and outlook Materials for sensors progressed as an Evolution: Molecular Materials: 0D 1D 2D 3D Fullerenes (C 60 ) 1D molecules 2D molecules 3D molecules Materials enable lots of opportunities Printed sensors on plastics, paper, textile etc. Gas and chemical sensors fabricated by printing process Flexible & stretchable sensors