Advanced Materials for Printed Flexible Electronics

Advanced materials for printed flexible electronics

Preface

1 Fundamentals and design guides for printed flexible electronics

            Abstract

1.1 Historical perspectives

1.2 Printing requirements for printable materials

1.2.1 Ink formulation

1.2.2 Inks for flexible devices

1.2.3 Inks for stretchable devices  

1.2.4 Inks for self-healing devices  

                        1.2.5 Polymer substrate formulation

            1.3 Design guidelines for flexible printed electronics

                        1.3.1 3D modeling and printing process control

                        1.3.2 Design guideline for 3D printing

                        1.3.3 Materials design for flexible and stretchable electronics

1.4 Fabrication technology for printed flexible electronics  

1.4.1 Nozzle-based 3D printing technologies

1.4.2 Light-based 3D writing technologies

1.4.2.1 Two-photon lithography

1.4.2.2 Projection micro-stereolithography

1.4.2.3 Continuous liquid interface production

1.4.3 Representative multi-material and hybrid 3D printing processes

1.4.4 Stress-controlled folding of 3D systems

1.4.4.1 4D printing

1.4.4.2 Micro- and nanoscale origami

1.4.4.3 Mechanically guided assembly

References

Exercises

 

2 Process and material characterization in printed flexible electronics

   Abstract

            2.1 Fluid characterization

                        2.1.1 Rheology and wetting behavior

                                    2.1.1.1 Viscosity

                                    2.1.1.2 Surface energies and surface tensions

                                    2.1.1.3 Viscoelasticity

                                    2.1.1.4   Direct imaging 

                                    2.1.1.5 Dynamic measurements

            2.1.2 Jet breakup and drop formation

2.1.3 Characteristics of jet fluids with solid fillers

            2.1.3.1 Rheology of particle suspensions

            2.1.3.2 Shear thinning fluids

            2.1.3.3 Phase-changing inks and three-dimensional printing

            2.1.4 Ink drop impact and reaction with substrate

                        2.1.4.1 Drop impact on powder and three-dimensional printed structures

                        2.1.4.2 Drop impact on textile surfaces

2.1.5 Solidification

2.1.6 Curing and sintering

            2.1.6.1 Thermal sintering

            2.1.6.2 Electrical sintering

            2.1.6.3 Photonic sintering

            2.1.6.4 Microwave sintering

2.2 Solid feedstock materials characterization techniques

2.2.1 Filament for fused deposition

2.2.1.1 Filament diameter consistency

2.2.1.2 Density

2.2.1.3 Porosity

2.2.1.4 Moisture content

2.2.1.5 Thermal properties

2.2.1.6 Microstructure analysis of composite filament

2.2.2 Powder for additive manufacturing processes

            2.2.2.1 Powder Morphology

                        2.2.2.1.1 Sieve analysis

                        2.2.2.1.2 Microcopy analysis

                        2.2.2.1.3 Laser light diffraction

                        2.2.2.1.4 Influence of particle size and size distribution on part properties

                        2.2.2.1.5 Effect of particle shape and surface roughness

            2.2.2.2 Powder chemistry

                        2.2.2.2.1 X-ray photoelectron spectroscopy

                        2.2.2.2.2 Auger electron spectroscopy

                        2.2.2.2.3 Energy dispersive X-Ray spectroscopy

                        2.2.2.2.4 Inductively coupled plasma optical emission spectroscopy

                        2.2.2.2.5 Inert gas fusion

                        2.2.2.2.6 Effect of powder chemistry

2.2.2.3 Powder microstructure

            2.2.2.3.1 Metallography

            2.2.2.3.2 X-ray diffraction

            2.2.2.3.3 Thermal analysis methods

2.3 Aerosol jet printing process characterization

            2.3.1 Working principle of aerosol jet printing

                        2.3.1.1 Atomization approach

                        2.3.1.2 Materials transport, focusing and deposition

                        2.3.2 Aerosol jet printing parameters

                                    2.3.2.1 Sheath and atomizer gas flow

                                    2.3.2.2 Tool path and design rules    

2.3.3 Future aerosol jet printing process modification and application

2.4 Printed thin-film characterization

2.4.1 Optical characterization

2.4.1.1 Optical microscopy

2.4.1.2 UV-Vis Spectroscopy

2.4.2 Additional surface topography

2.4.2.1 Stylus profilometry

2.4.2.2 Confocal and white-light microscopy

2.4.2.3 Atomic force microscopy

2.4.3 Electrical conductivity measurement

2.5 Mechanical characterization of printed flexible electronics

            2.5.1 Determining materials constants

            2.5.2 Bending deformation

            2.5.3 Stretching deformation

            2.5.4 Shear and twisting deformation

            2.5.5 Adhesion, cohesion and scratch testing

            2.5.6 Impact resistance

2.6 Durability of flexible electronics

            2.6.1 Engineering stress distribution across layers

            2.6.2 Nanoribbons and nanomembranes

            2.6.3 Separation of brittle components

2.6.4   Future perspectives

References

Exercises

 

 

3 Conductive materials for printed flexible electronics

   Abstract

3.1 Introduction

3.2 Advanced metal-based materials for micro-/nano-scale 3D printing

            3.2.1 Metal nanoparticles

                        3.2.1.1 Synthesis of metal nanoparticles

                        3.2.1.2 Stabilization of dispersed metal nanoparticles against aggregation

                        3.2.1.3 Stabilization of metal nanoparticles against oxidation

                        3.2.1.4 Formulation of metal-based conductive inks

                        3.2.1.5 Metal-based conductive inks for printing 3D structures

            3.2.2 Metal nanowires

            3.2.3 Liquid metal inks

            3.2.3 Reactive metal inks

3.3 Carbon based materials

            3.3.1 Graphene based inks

3.3.2 Carbon Nanotube based inks

3.4 Transparent oxide conductors

3.4.1 Low Temperature Solution Processing

3.4.2 Doped Transparent Oxide Nanoparticles

3.5 Conductive polymer inks

3.6 Perspectives and future development trends of conductive inks

3.6.1 Traditional polymer thick film inks

3.6.2 Printing inks for in-mold electronics

3.6.3 Stretchable conductive inks

3.6.3.1 Sputtering/etching or laser-cutting conductive films on stretchable substrates

3.6.3.2 Embedding stretchable conductive materials in stretchable substrates

3.6.3.3 Thinning or developing meandering patterns

                        3.6.3.3.1 Pre-strained substrate approach

                        3.6.3.3.2 Localized node bonding approach

                        3.6.3.3.3 Helix structure approach

3.6.4 Enabling limited stretchability by printing conductive ink on stretchable substrates

References

Exercises

 

4 Semiconducting and dielectric materials for printed flexible electronics

   Abstract

            4.1 Introduction

4.2 Flexible inorganic semiconducting materials

4.2.1 Thin films of silicon

4.2.2 Films of transparent oxides

            4.2.2.1 ZnO films deposited from the gas phase

            4.2.2.2 ZnO films spin-cast from colloidal solutions

            4.2.2.3 Films of ZnO-based binary and ternary oxides

4.2.3 Films of chalcogenides

            4.2.3.1 Films of chalcogenide nanocrystals

            4.2.3.2 Films of chalcogenides derived from liquid precursors

4.2.4 Nanoscale inorganic semiconductors formed with bottom-up approaches

4.2.5 Nanoscale inorganic semiconductors formed with top-down approaches

4.3 Organic semiconductors for flexible electronics

            4.3.1 Historical perspective

            4.3.2 Material types

            4.3.3 Basic properties of organic semiconductors

4.3.3.1 Physical properties

4.3.3.2 Optical properties

4.3.3.3 Charge carrier transport

4.3.4 Architectures and properties of organic semiconductor devices

4.3.5 Organic semiconductor structural design in printed electronics

4.4 Printable organic small molecular semiconductors

            4.4.1 p-type small molecular semiconductors

            4.4.2 n-type small molecular semiconductors

4.5 Printable polymeric semiconductors

            4.5.1 p-type conjugated polymer semiconductors

            4.5.2 n-type conjugated polymers

            4.5.3 Perspectives of solution-processed polymer semiconductors

4.6 Composite organic semiconductors

            4.6.1 Polymer-fullerene bulk heterojunctions

            4.6.2 Polymer-polymer semiconductor composites

            4.6.3 Organic-inorganic composites of semiconductor nanocrystals

            4.6.4 Nanoconfinement of polymer semiconductors with improved stretchability

References

Exercises

 

5 Insulating and encapsulating materials for printed flexible electronics

   Abstract

            5.1 Substrate materials 

                        5.1.1 General requirements for flexible substrates

5.1.2 Types of substrate materials

            5.1.2.1 Polymer substrate materials

            5.1.2.2 Inorganic substrate materials

            5.1.2.3 Fibrous substrate materials

5.2 Dielectric materials

            5.2.1 Inorganic dielectrics

            5.2.2 Polymer dielectrics

                        5.2.2.1 Poly(vinyl alcohol)

                        5.2.2.2 Cyanoethyl polymers

                        5.2.2.3 Poly(vinylidene fluoride) and its copolymers

            5.2.3 Electrolyte dielectrics

                        5.2.3.1 Polymer electrolytes

                        5.2.3.2 Polyelectrolytes

                        5.2.3.3 Ionic liquids

                        5.2.3.4. Ion-gels

            5.2.4 Hybrid dielectrics

5.2.4.1 Self-assembled nano-dielectrics

5.2.4.2 Inorganic/polymer blends

5.3 Encapsulation

            5.3.1 Encapsulation evaluation methods

            5.3.2 Traditional encapsulation approaches

5.3.3 Chemical vapor deposition technology for encapsulation

5.3.4 Atomic layer deposition for encapsulation

5.3.5 Thin film encapsulation for flexible devices

References

Exercises

 

6 Printed flexible thin film transistors

    Abstract

6.1 Types of transistors

6.1.1 Bipolar junction transistors

            6.1.1.1 NPN transistor

             6.1.1.2 PNP transistor

6.1.2 Field effect transistors

           

6.1.2.1 Junction-field effect transistor

                        6.1.2.2 Metal-oxide-semiconductor field-effect transistor

            6.1.3 Other emerging transistors

6.2 Structure and operation of thin film transistors

6.3 Printing techniques and printed components of thin film transistors

            6.3.1 Printing techniques

6.3.2 Printed TFTs on rigid substrate

                        6.3.2.1 Printed semiconductor layer

6.3.2.1.1 Organic semiconductor

6.3.2.1.2 Carbon-based semiconductor

6.3.2.2 Printed dielectric layer

6.3.2.3 Printed electrodes

6.3.2.4 Fully printed TFTs

6.3.3 Printed TFTs on flexible substrate

6.3.3.1 Polymer substrates

6.3.3.1.1 Partly printed TFTs on flexible substrate

6.3.3.1.2 Fully printed TFTs on flexible substrate

6.3.3.2 Paper substrate

6.4 Printed organic thin film transistors

6.4.1 Materials for OTFTs

6.4.1.1 Organic semiconductors

6.4.1.2 Gate dielectrics in OTFTs

6.4.1.3 Other materials used in OTFTs

6.4.2. Device structures used for OTFTs

6.4.3 Manufacturing process and integration of OTFTs

6.4.3.1 Processes compatible with established industry facilities

6.4.3.2 Full printing processes for OTFTs

6.4.3.3 Challenges and outlook for OTFT technologies

6.5 Printed inorganic thin film transistors

6.5.1 Printed oxide transistors

            6.5.1.1 Vacuum deposition- based metal oxide TFTs

            6.5.1.2 Solution-processed n-type metal oxide semiconductors

6.5.1.2.1 Basics of sol-gel oxide chemistry

6.5.1.2.2 Low-temperature route for solution-processed n-type oxide semiconductors

            6.5.1.2.2.1 Novel precursor approaches

            6.5.1.2.2.2 Novel post-treatment methods

6.5.1.2.3 Current challenges in solution-processed n-type oxide semiconductors

6.5.1.3 Solution -processed p-type metal oxide semiconductors

6.5.1.3.1 Basics of p-type oxide semiconductors

6.5.1.3.2 Copper Oxide

6.5.1.3.3 Tin monoxide

6.5.1.3.4 Nickel oxide

6.5.1.3.5 Current challenges in solution-processed p-type oxide semiconductors

6.5.2 Carbon nanotubes for thin film transistors

6.5.2.1 SWCNT-TFT fabrication

6.5.2.1.1 CNT Fabrication

6.5.2.1.2 Separation of metallic and semiconducting CNTs 

6.5.2.1.3 CNT film fabrication process

6.5.2.1.4 SWCNT-TFT structure and fabrication process

6.5.2.2 Electrical, optical and mechanical properties of SWCNT-TFTs

            6.5.2.2.1 Electrical properties

            6.5.2.2.2 Optical Properties

            6.5.2.2.3 Mechanical properties

6.5.2.3 Outlook on carbon nanotubes based thin film transistors

6.5.2.3.1 Alignment

6.5.2.3.2 Metal contact

6.5.2.3.3 Semiconducting CNT purity

6.5.2.3.4 N-Type Device

6.5.2.3.5 Integration

6.5.3 Thin film transistors based on graphene and graphene/semiconductor heterojunctions

            6.5.3.1 Graphene acting as channel material in thin film transistors

            6.5.3.2 Graphene acting as electrode material in thin film transistors

6.5.3.2.1 Preparation of graphene/semiconductor heterojunctions

6.5.3.2.1.1 Mechanical stacking method

6.5.3.2.1.2 Direct CVD growth of 2D nanomaterials heterostructures

6.5.3.2.2 Graphene/inorganic semiconductor heterojunction TFTs

6.5.3.2.3 Graphene/organic semiconductor heterojunction TFTs

6.5.3.3 Outlook on graphene based thin film transistors

6.5.4 High-mobility thin-film transistors based on multilayer 2D materials

6.5.4.1 Rationale

6.5.4.2 Common 2D materials for TFTs

6.5.4.3 Applications of 2D TMDs TFTs

6.5.4.3.1 Flexible devices

6.5.4.3.2 Transparent devices

6.5.4.3.3 Opto-electronic devices: sensitive photodetectors

6.5.4.4 Outlook on high-mobility thin-film transistors

References

Exercises

 

7 Printed flexible light-emitting diodes

   Abstract

            7.1 Introduction

7.2 Working principle of organic light-emitting diodes

7.2.1 Basic light phenomena

7.2.1.1 Incandescence

7.2.1.2 Luminescence

            7.2.1.2.1 Photoluminescence

            7.2.1.2.2 Electroluminescence

7.2.2 OLED device structure

7.2.3 OLED working

7.2.4 OLED classification

7.2.5 OLED characterization

            7.2.5.1 Internal quantum efficiency

            7.2.5.2 External quantum efficiency

            7.2.5.3 Outcoupling efficiency

            7.2.5.4 Efficacy

            7.2.5.5 Lifetime issues

            7.2.5.6 Routine testing for performance evaluation of OLED device

                        7.2.6 OLED fabrication techniques

                                    7.2.6.1 Physical vapor deposition

                                    7.2.6.2 Screen printing

                                    7.2.6.3 Ink-jet printing

                                    7.2.6.4 In-line fabrication

                                    7.2.6.5 Roll to roll process

7.3 General materials and components of OLEDs

7.3.1 Substrate

7.3.2 Anode

7.3.3 Cathode

7.3.4 Organic emissive materials

7.3.5 Amorphous molecular materials for hole- and electron-transporting

            7.3.5.1 Hole-transporting amorphous molecular materials

            7.3.5.2 Electron-transporting amorphous molecular materials

7.3.6 Solution-processable OLED materials

7.3.7 Encapsulation for OLEDs

7.4 White lighting OLEDs

            7.4.1 White light emission mechanism

                        7.4.1.1 White light emission from small-molecule-doped polymer films

7.4.1.1.1 Fluorescence-emitting dopants

7.4.1.1.2 Phosphorescent emitters

7.4.1.1.3 Hybrid fluorescent blue/phosphorescent green and red systems

7.4.1.2 White emission from multiple light-emitting polymers

7.4.1.2.1 Blended polymeric systems

7.4.1.2.2 White light from polymer heterolayers

7.4.1.3 Single-component polymer systems

7.4.1.3.1 Conjugated copolymers comprising main-chain chromophores

            7.4.1.3.2 Copolymers with side-chain chromophores

7.4.1.4 Outlook on the development of polymer white OLEDs

7.4.2 White OLEDs based on small molecules

7.4.3 Light outcoupling improvement and efficiency limitation of white OLEDs

7.5 Flexible quantum dot light-emitting diodes

            7.5.1 Material design for efficient QLEDs

            7.5.2 Device structures and operation principles of QLEDs

            7.5.3 Patterning technology of QDs for full-color displays

            7.5.4 Flexible white QLEDs

            7.5.5 Flexible transparent QLEDs

            7.5.6 Potential applications of flexible QLEDs

            7.5.7 Outlook on flexible and wearable QLEDs

References

Exercises

 

8 Printable solar cells from solution-processible materials

   Abstract

8.1 Operating principles of printable solar cells

            8.1.1 Fundamentals of solar cells

            8.1.2 Device structure

8.1.3 Operating principles

8.1.4 Performance characteristics

8.1.4.1 Fill factor

8.1.4.2 Open circuit voltage

8.1.4.3 Short circuit current density

8.1.4.4 Absorption coefficient

8.1.4.5 Recombination and diffusion length

8.1.4.6 Photovoltaic cell efficiency limit

8.2 Solution-processed organic polymeric solar cells

8.2.1 Historical perspective

8.2.2 Tandem solar cells 

8.2.2.1 Interconnecting layer materials

8.2.2.2 Processing multijnction stacks and light management

8.2.2.3 Active layer materials

8.2.2.4 Upscaling

8.3 Solution-processed inorganic CIGS/CZTS thin-film solar cells

8.4 Organic-inorganic hybrid perovskite solar cells

8.5 Outlook and future perspective

References

Exercises

 

9 Printed flexible electrochemical energy storage devices

9.1 Perspectives on electrochemical energy storage

            9.1.1 Classification of electrochemical energy storage

                        9.1.1.1 Basic battery operation

                        9.1.1.2 Basic operation of capacitor and supercapacitor

            9.1.2 Miniaturization of electrochemical energy storage devices for flexible/wearable electronics

9.2 3D printing for electrochemical energy storage applications

9.2.1 Printing technologies for electrochemical energy storage device fabrication

            9.2.1.1 Basic 3D printing systems and processes

            9.2.1.2 Materials considerations

9.2.2 Performance optimization strategies

9.2.2.1 Performance metrics

9.2.2.2 Optimization strategies

9.2.3 Advances in 3D-printed electrochemical energy storage devices

            9.2.3.1 Sandwich-type configurations

            9.2.3.2 In-plane configurations

9.2.4 Outlook on printed electrochemical energy storage devices

9.3 Printed battery architectures

9.3.1 Printing technique adoption

9.3.2 Preparation of battery component inks

9.3.2.1 Printed electrodes

9.3.2.2 Printed electrolytes and separator membranes

9.3.3 Electrochemical performances of printed batteries

9.3.4 Advances in printed battery systems and their applications

            9.3.4.1 Zn-based batteries

            9.3.4.2 Li-ion batteries

9.3.5 Perspectives and future development directions

9.4 Printed flexible supercapacitors

9.4.1 Device structures of printed supercapacitors

9.4.2 Printable materials for supercapacitors

            9.4.2.1 Electrode materials

                        9.4.2.1.1 Carbon-based electrode materials

                        9.4.2.1.2 Metal-based electrode materials

                        9.4.2.1.3 Conducting polymers

                        9.4.2.1.4 2D nanomaterials beyond graphene

                        9.4.2.1.5 Metal-organic frameworks

9.4.2.2 Electrolytes

            9.4.2.2.1 Aqueous gel polymer electrolytes

            9.4.2.2.2 Organic gel polymer electrolytes

            9.4.2.2.3 Ionic liquid-based gel polymer electrolytes

            9.4.2.2.4 Redox-active gel electrolytes

9.4.2.3 Current collectors

            9.4.2.3.1 Metal current collectors

            9.4.2.3.2 Carbon-based current collectors

                        9.4.2.4 Substrates

                                    9.4.2.4.1 Metal foils

                                    9.4.2.4.2 Polymer-based plastic substrates

                                    9.4.2.4.3 Paper substrates

9.4.3 Advances of printed supercapacitors

            9.4.3.1 Inkjet printing

            9.4.3.2 Screen printing

            9.4.3.3 Three-dimensional (3D) printing

            9.4.3.4 Transfer printing

            9.4.3.5 Pen-based direct ink writing

            9.4.3.6 Roll-to-roll (R2R) printing

            9.4.3.7 Patterned coating methods

            9.4.3.8 Outlook on printed supercapacitors

9.4.4 Applications of printed supercapacitors

            9.4.4.1 Multifunctional supercapacitors

            9.4.4.2 Supercapacitors working as power units for sensors

            9.4.4.3 Supercapacitors working as energy storage units for ambient energy sources

9.4.5 Challenges and future perspectives

9.5 Printed Supercapacitor Architectures

9.5.1 Printable High-Surface Area Materials

9.5.2 Printable Supercapacitors

9.6 Challenges of Printed Electrochemical Systems

References

Exercises

10 Printed flexible sensors and sensing systems

10.1 Introduction

10.2 Working principle of sensors

10.3 Printable materials and component integration

10.3.1 Substrates for flexible sensors

10.3.2 Conducting materials

            10.3.2.1 Metals

            10.3.2.2 Amorphous oxide conductors

            10.3.2.3 Carbon conductors

            10.3.2.4 Organic Conductors

10.3.3 Semiconductors

            10.3.3.1 Metal oxide semiconductors

            10.3.3.2 Organic semiconductors

            10.3.3.3. Flexible silicon

            10.3.3.4 Transition metal dichalcogenides

            10.3.3.5 Black phosphorus

            10.3.3.6 Perovskites

10.3.4 Dielectric materials

10.4 Printed flexible sensors

            10.4.1 Printable pressure sensors

                        10.4.1.1 Piezoresistive sensors

                        10.4.1.2 Piezoelectric sensors

                        10.4.1.3 Piezocapacitive sensors

                        10.4.1.4. Triboelectric sensors

10.4.2 Printable strain sensors

10.4.3 Temperature sensors

10.4.4 Humidity sensors

10.4.5 Magnetic sensors

10.4.6 Chemical Sensors

10.4.7 Electromagnetic radiation sensors

10.4.8 Multi modal sensors

10.4.9 Electropotential sensors

10.4.10 Ultrasonic sensors

10.5 Integration of printed sensors into systems

10.6 Future perspectives

References

Exercises

 

11 Printed flexible hybrid electronics

     Abstract

11.1 State-of-the-art development

            11.1.1 The roles of printed electronics and standard silicon integrated circuits

            11.1.2 The merit of flexible hybrid electronics

11.2 Core components of the flexible hybrid electronics

11.2.1 Substrate

11.2.2 Inks and printing techniques

11.2.3 Printed sensors and circuits    

11.3 Thinned silicon ICs and assembly process in FHE

11.3.1 Thinning Silicon ICs and Connecting to FHE

11.3.2 Conductive and nonconductive adhesives

11.3.3 Assembly process for rigid components in FHE

11.4 Printed antennas for wireless power and communications

11.4.1. Printed antennas for communication purposes

11.4.2 Printed coils for wireless power transfer       

11.5 Printed power sources - Batteries, solar cells, and energy harvesters

11.5.1 Printed energy-storage modules

11.5.2 Printed energy-harvesting modules

11.6 Quality assurance

            11.6.1 High-resolution patterning

            11.6.2 Uniformity

            11.6.3 Flexibility/Stretchability

            11.6.4 Durability

            11.7 Reliability evaluation

            11.8 Application

                        11.8.1 Wearable Health Monitoring with FHE

                        11.8.2 Industrial, environmental, and agricultural monitoring with FHE

                        11.8.3 Structural health monitoring with FHE

            11.9 Challenges and future trends

References

Exercises

12 Perspectives and current trends in printed electronics manufacturing

      Abstract

12.1 Introduction

12.2 Electronic materials and components

12.3 Techniques and processes in printed electronics

12.3.1 Techniques in printed electronics

            12.3.1.1 2D printing technologies

            12.3.1.2 3D printing technologies

            12.3.1.3 4D printing technologies

12.3.2 Processes in 3D printing electronics

            12.4 Current trends in 3D printed electronics

12.4.1 Research and development

            12.4.1.1 Common devices

            12.4.1.2 Antennas

12.4.1.3 Flexible electronics

12.4.1.4 Batteries

12.4.2 Integrated 3D-printig systems for mass production

References

Exercises