Polymer Materials: from Electrets to Organic Electronics

Prof. Roberto Mendonça Faria (IFSC/USP)
Polymer Materials: from
Electrets to Organic Electronics
Roberto Mendonça Faria
Instituto de Física de São Carlos, Universidade de São Paulo

Focus of this Lecture
- Short history of the Bernhard Gross Polymer Group of the São
Carlos Institute of Physics, USP;
- network research organizations: (i) Millennium Institute of
Polymer Materials (IMMP - 2002-2008), and (ii) National Institute
of Science and Technology on Organic Electronics (INEO - 2009 -
2023);
- brief reports of the most relevant researches along 40 years on
electrical properties of polymer films and on organic electronics.

PRECURSORS OF MATERIALS SCIENCE IN
BRAZIL
Prof. Bernhard Gross Prof. Joaquim da Costa Ribeiro
Considered the father of modern electret
Developed pioneering models on viscoelasticity
Rheology
First scientist to describe the thermodielectric effect

Group of Electrect (1973-1990)

Group of Electrets – IFQSC/USP (Early 1970)
Faculty (1975):
Guilherme Fontes Leal Ferreira
Milton Soares de Campos
Renê A. Alfaro Moreno
Emeritus affiliate:
Bernhard Gross
Graduate students:
José Alberto Giacometti
Luis Nunes de Oliveira
Roberto Mendonça Faria
Sérgio Mergulhão
Osvaldo Novais de Oliveira Jr.

Faculty (1980s):
Guilherme Fontes Leal Ferreira
Milton Soares de Campos
José Alberto Giacometti (1977)
Roberto Mendonça Faria (1977)
Mariângela T. Figueiredo (1979)
Osvaldo Novais de Oliveira Jr. (1985)
Emeritus affiliate:
Bernhard Gross
Graduate students:
More than 30
Group of Electrets – IFQSC/USP (1980s)

First Meeting of Condesend Matter (1978)
SBF – Cambuquira/MG

SBQ and CBECIMat Meetings
Since 1978 Since 1974

Insulating polymers
(Late 1970s and 1980s)
ELECTRETS

MAGNET AND ELECTRETS
Magnet
External Magnetic Field
Space charge Electret
External Electric Field
Polar Electret
External Electric Field

POLYMER ELECTRETS
Teflon FEP
Space charge Surface charges Oriented dipoles

CORONA DISCHARGE
B. Gross, G. F. Leal Ferreira, O. N. Oliveira Jr., J. Appl. Phys. 58, 1487-1491 (1984)
J.A. Giacometti, Rev. Sci. Inst. 89, 055109 (2018)
R. A. Moreno & B. Gross, J. Appl. Phys. 47(8), 3397-3402 (1976)
B. Gross, J. A. Giacometti, G. F. Leal Ferreira, IEEE Transactions on Nuclear Science, NS-28 (6), 47(8), 4513-4522 (1981)

First project on electret microfones
(IFQSC and Eletroacúscita Co, supported by Telebrás)

ELECTRET MICROPHONE
Market of electret microphones (2022)  1.2 billions of USD

Insulating polymers
(Late 1970s and 1980s)
RADIATION EFFECTS

RADIATION INDUCED CONDUCTIVITY
B. Gross, R. M. Faria & G. F. Leal Ferreira, J. Appl. Phys. 52(2), 571-577 (1981)
A. Tyutnev, V. Saenko, A. Zhadov, E. Pozhidaev, Polymers 11(12), 2061-2074 (2019)

Compton Current
B. Gross, R. M. Faria & G. F. Leal Ferreira, J. Appl. Phys. 52(2), 571-577 (1981)
Angular distribution of Compton electrons
Compton scattering

Insulating polymers
(Along1980s)
FERROELECTRICITY

FERROELECTRIC POLYMERS
Polyvinylidene Fluoride (PVDF) Poly(Vinylidene Fluoride – Tri-Fluoroethylene)
Prof. Eiichi Fukada

Second project on piezo microfones
(IFQSC and Eletroacúscita Co, supported by Telebrás)

APPLICATIONS OF FERROELECTRIC
POLYMERS

Studies on Ferroelectric
Polymers and Piezoelectricity

Ferroelectric phase transitions:
Pyroelectric current and piezoelectric noise
R. M. Faria, J. M. G. Neto & O. N. Oliveira Jr., J. Php. D: Appl. Phys. 27. 611-615 (1994)
Poly(Vinylidene Fluoride – Tri-Fluoroethylene): P(VDF-TrFE)
Thermally Stimulated Depolarization and Dielectric Constant measurements

DC Piezoelectricity
Corona discharging, heat pulse and piezo measurements
R. M. Faria, Appl. Phys. Lett. 69, 1972-1976 (1996)
Space charge electrets (non polar)

DC Piezoelectricity
No current signal under
mechanical stress
𝑥 = 0
𝐿
𝑥𝜌 𝑥 𝑑𝑥
0
𝐿
𝜌 𝑥 𝑑𝑥
=
𝜀𝑉
𝜎
𝑑𝑥
𝑑𝑋
=
𝑑
𝜌
R. M. Faria, Appl. Phys. Lett. 69, 1972-1976 (1996)
Heating process
Compression
Decompression

In 1990
Group of Electrets 
Electronic polymers come on the scene

Inorganic semiconductor: silicon
Intrinsic crystal

Trans-POLYACETYLENE
Ethylene:  and  orbitals
Dimerization (HOMO and LUMO)

Defects: Solitons and excitons
A B
Molecular
exciton
B

Excitons, polarons and bipolarons

Researches on electrical properties of
organic semiconductors
(1990s)

Oxidation states of polyanilines
J.E. Albuquerque, L.H.C. Mattoso, D.T. Balogh, R.M. Faria, J.G. Masters,
A.G. MacDiarmid, Synth. Met. 113 19–22 (2000)

Thermal conductivity vs Electric conductivity
J. E. De Albuquerque, W. L. B. Melo, R. M. Faria, J. Polym. Sci. Part B:
Pol. Phys. 38, 1294-1300 (2000)
Polyaniline sample Undoped Doped (HCl 10-3 M) Doped (HCl 1 M)
Ks (W/mk) 7.44 x 10-2 7.52 x 10-2 7.95 x 10-2
Photothermal spectroscopy (pyroelectric chamber)

Millennium Institute of Polymer Materials
(2002 – 2008)
IMMP

First BMRS
Meeting
Rio de Janeiro, july 7-10, 2002
SYMPOSIUM A
Current trends in nanostructured materials and systems
SYMPOSIUM B
Advances in the development of biomaterials
SYMPOSIUM C
Boundaries in semiconductor materials and devices
SYMPOSIUM D
III Brazilian Electroceramics Symposium
SYMPOSIUM E
Surface modification in polymeric materials and thin films
WORKSHOP
Particulate materials: processing, properties and applications

National Institute of Science and Technology on
Organic Electronics (2009 – 2023)

XX BMRS Meeting
SYMPOSIUM E
Energy Harvesting: Perovskite, Organic, Hybrid, Quantum Dots, and Dye-Sensitized Solar
Cells
SYMPOSIUM R
Organic Electronics, Photonics and Bioelectronics: Fundamentals, Applications and
Emerging Technologies

Researches on Electronic and
Optoelectronic Devices
(Since the end of 1990s)

Field effect transistor using POMA films: OFET
C.F.O. Graeff, R.K. Onmori, F.E.G. Guimarães & R.M. Faria, Synt. Met. 105, 151-152 (1999)
R. F. Bianchi, R. K. Onmori & R. M. Faria, J. Polym. Sci. B: Polymer Physics, 43, 74–78 (2005)

OLEDs and OLECs
C. A. Olivati, R. M. Faria, R. F. Bianchi, D. T. Balogh, R. K. Onmori, A. M. Andrade, Synth. Met. 121(1-3), 1579-1580 (2001)
L. F. Santos, L. M. Carvalho, F. E. G. Guimarães, D. Gonçalves, R. M. Faria, Synth. Met. 121 (1-3), 1697-1698 (2001)

White OLED
J. F. de Deus, G. C. Faria, R. M. Faria, E. T. Iamazaki, T. D.Z. Atvars, A. Cirpan, L. Akcelrud, Journal of Photochemistry and
Photobiology A: Chemistry 253, 45– 51 (2013)

OPVs
R. K. Onmori, C. A. Olivati, R. F. Bianchi, R. M. Faria, A. M. Andrade, Synth. Met. 121, 1577-1578 (2001)

BHJ-OPVs
Active layer thickness: 100 to 200 nm

Donor and acceptor molecules
Non fullerene acceptors

Solar cell: J-V curve and equivalent circuit
Dark
Under illumination
V

BHJ Organic Solar Cell: Efficiency
Main reasons for low efficiency of BHJ-OSCs:
- low mobility and high recombination
TSol = 5.778 K
TTerra = 300 K
...............................................................................................................................

Photo-CELIV, TOF, TPV, and TPC techiques
Stationary techniques
Transient technique
Gregório C. Faria
D. R. B. Amorim, M. R. P. da Silva, D. J. Coutinho, G. C. Faria

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
D. J. Coutinho, G. C. Faria, D. T. Balogh, Solar Energy Materials & Solar Cells 143,
503-509 (2015)
𝐽𝑝ℎ(v) = 2𝑒𝐺𝑃𝐿
1−
𝑉
𝑉𝑏𝑖
2
𝜃𝑜
1 +
𝜃𝑜
1−
𝑉
𝑉𝑏𝑖
2 − 1 , 𝜃𝑜=
GPL
4
1−𝑃 𝛾𝐿
(μ𝑉𝑏𝑖)
2 .
D. R.B. Amorim, D. J. Coutinho, P. B. Miranda & R. M. Faria, Phys. Rev. App. 14,
034046 (1- 9) (2020)
J-V: Recombination of first order kinetics
J-V: Recombination of second order kinetics
CT states: geminate recombination
Nongeminate recombination
J-V: Analytical models

Transient characterization
Experimental setup
Response only under
continuous white light Response after the
incidence of a laser pulse
M. R. P. da Cunha, D. R. B. Amorim, G. C. Faria, D. J. Coutinho & R. M. Faria, Solar Energy Materials & Solar Cells 231 (1-8),
111313 (2021)

-RL Response
101
102
103
104
105
106
107
0.1
1
10
Tempo
de
decaimento
(
ms
)
RL (W)
I II III

m
M. R. P. da Cunha, D. R. B. Amorim, G. C. Faria, D. J. Coutinho & R. M. Faria, Solar Energy Materials & Solar Cells 231 (1-8),
111313 (2021)

101
102
103
104
105
106
107
0.1
1
10
Tempo
de
decaimento
(
ms
)
RL (W)
I II III

m
-RL vs J-V
0.0 0.2 0.4 0.6 0.8 1.0
-16
-14
-12
-10
-8
-6
-4
-2
0
2
J(mA/cm
2
)
V(V)
Model
Equation
Plot
Rs
Rsh
Jph
Js
n
Vt
S
Reduced Chi-Sqr
R-Square (COD)
Adj. R-Square
I II III

-RL for different intensities of sunlight

Equivalent circuit for transients

ACKNOWLEDMENTS

Polymer Materials: from Electrets to Organic Electronics

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