ICT role in 21st century education and it's challenges.
Lead-free materials for harvesting and sensing electronics
1. Lead-free materials – application in the
energy harvesting and sensing electronics
Mariya Aleksandrova
e-mail: m_aleksandrova@tu-sofia.bg
Department of Microelectronics,
Faculty of Electronic Engineering and Technology,
Technical University of Sofia, Bulgaria
1
28-29-Apr-21
2. 2
28-29-Apr-21
Outline:
• Brief introduction to the recent group’s research activities
• Problem definition – efficient energy conversion and sensing sensitivity
• Current and future trends in the field of microelectronic (thin-film
based) piezoelectric and solar converters
• Flexible and nanostructured lead-free piezoelectric energy harvesting
and sensing elements – materials selection, technology aspect, signal
processing
• Perovskite lead-free solar energy harvesting and sensing elements –
materials selection, technology aspect, signal processing
• Future work
• List of collaborators and list of relevant papers of the team
3. 28-29-Apr-21 3
• Brief introduction to the recent group’s research activities
Thin-film solar cells with eco-friendly nanocoatings.
Flexible Light-Emitting Devices
(f-LED) with organic and
inorganic materials.
Lead-Free Flexible Energy Harvesters
and Wearable Sensors producing
electrical charges from the human
motion due to piezoelectric effect.
4. 28-29-Apr-21 4
• Problem definition
The conversion of energy from various
sources at the surrounding environment
(energy harvesting) solves the problem of
battery-less power supply and satisfies the
modern concepts of "clean" energy.
However, not all of them solve the problem
with the compactness.
Normally, the energy harvesting devices are bulk converting elements with relatively large
dimensions that should be decreased, but their efficiency should not be reduced, which is
hard task.
In addition, the most effective energy converting materials are lead or arsenide
containing, so they are not environmentally friendly.
5. 28-29-Apr-21
5
• Current and future trends in the field of piezoelectric
and solar converters
Piezoelectric nanogenerators (PENGs) can be designed compact (thin films grown on plastic
substrates), lightweight, sensitive to weak activating stimuli and can be partially integrated
on the same microchip with the sensor elements.
Some PENGs materials can be used for sensing elements due to their ferroelectric behavior -
tire pressure sensors in the automotive industry, vibrational diagnostics for equipment
condition monitoring, measurement of the ambient temperature and atmospheric
pressure, pyroelectric sensors for motion detecting, etc.
They still need a lot of technology optimizations to enhance their electrical performance and
mechanical stability.
https://acrobotic.com/products/sen-00020
https://ec.kemet.com/blog/pyroelectric-
sensors-for-motion-gas-food-or-flame/
Harvester
Sensor
Direct integration
on one microchip!
6. 28-29-Apr-21 6
The same is valid for the thin film solar energy harvesters with perovskites –
successful integration of harvesting and photosensor capabilities.
https://www.nature.com/articles/d41586-019-01985-y, 2019
Recently the focus of the researchers working in the
field of solar energy harvesting was put on the lead-
halide Perovskite materials, which were found to
convert over 25% of the sun energy into electricity
(similar to the polycrystalline silicon), but allowing
compactness (thin films) and low-cost fabrication.
Introduction of quantum dots (QDs)
are used to precisely tune the
properties of the solar converting
devices.
Mashinchian et al.,BioImpacts, 2014, 4(3), 149-166
They still need investigation of their
compatibility, performance and stability.
7. 28-29-Apr-21 7
By our research we aim:
1) Technological compatibility with the flexible substrates (low temperature processes
on plastic) and specific patterning of the areas (reverse lift-off photolithography) so
that they experience maximum mechanical load (or solar exposure, if they are light
harvesters);
2) Application of environmentally friendly materials.
3) Nanostructuriing of the materials to improve the harvesting yield and the sensor
properties of the devices. Preparation of complex oxides and polymers with
controllable morphology at nanoscale level, in particular nanorods, nanowires,
nanodendrite formations, with adjustable size, in order to increase the specific area
and thus to improve its sensitivity by achieving a high surface-to-volume ratio across
the total material thickness.
8. 28-29-Apr-21 8
• Flexible and nanostructured piezoelectric energy harvesting and sensing
elements – materials selection, technology aspect, signal processing
SEM images of the surface morphology of nanobranched ZnO and Ga-doped ZnO
grown on seed PEDOT:PSS conductive polymer
5 10 15 20 25 30 35 40 45
0
50
100
150
200
250
300
350
piezoelectric
voltage,
mV
mass load, g
PEDOT: PSS
bottom electrode
Al bottom
electrode
10 20 30 40 50 60 70 80
0
2
4
6
8
10
strain
current,
A
current
0
1
2
3
4
5
6
7
power
density,
W/cm
2
power density
Organic/inorganic interface production – replacing
the conventional electrodes with conductive polymer
9. 28-29-Apr-21
9
Nanowires of KNbO3 were grown by filling nanoporous templates of both side opened
anodic aluminum oxide (AAO) through radiofrequency vacuum sputtering for multisensor
fabrication. The precise geometrical ordering of the AAO matrix led to well defined single
axis oriented wire-shaped material inside the nanopores/nanotubes.
10 20 30 40 50 60
1
2
3
4
5
6.3 m
1.3 m
10 m
pyroelectric
voltage,
V/m
2
C
o
temperature, C
o
This approach of nanostructuring
results in voltage doubling caused
from the piezo- and pyroelectric
effects due to the “concentrators
effect”.
10. 28-29-Apr-21 10
Pressure sensors on bulk micromachined
silicon membrane with lead-free
piezoelectrics - BaSrTiO3, KNbO3, ZnO:Ga
Printing of piezoelectric ink - polymer PVDF-TrFE
for enhancing the mechanical durability at cyclic
multiple bending
poly[(vinylidenefluoride-
co-trifluoroethylene] -
P(VDF-TrFE)
0 200 400 600 800
20
40
60
80
100
Voltage,
mV
Load, g
0.5 1.0 1.5 2.0 2.5 3.0
200
250
300
350
400
450
fresh
after 1000 cycles
generated
voltage,
mV
mass load, kg
0.7 kV, Ar=2.10-2
Torr 0.9 kV, Ar=2.10-2
Torr 1.1 kV, Ar=2.10-2
Torr
1.3 kV, Ar=2.10-2
Torr 1.1 kV, Ar =9.10-4
Torr 1.1 kV, Ar=6.10-1
Torr
97.49 nm
0.00 nm
94.03 nm
0.00 nm
103.37 nm
0.00 nm
194.04 nm
0.00 nm
192.21 nm
0.00 nm
215.98 nm
0.00 nm
This reduces the surface roughness at nanoscale
and improves the contact conditions.
11. Designed interface circuit for the sensing
elements based on a dynamically
programmed Field Programmable Analog
Array (FPAA), realizing Root-Mean-Square
(RMS) to DC (RMS-to-DC) conversion.
IN
OUT-
OUT+
F
R
F
R
ref
Differential
signal
V
5
,
1
FPAA
N
R
p
R
CC
V
CC
V
k
10
k
10
k
10
k
10
1
U
6024
MCP
1
D 2
D
GND ref
Output grounded
signal
RMS
U
0
20
40
60
80
100
120
140
160
0 20 40 60 80 100
Samples
V
RMS
,
mV
VRMS,min=124mV
VRMS,max=138.3mV
VRMS,avg=131.95mV
∆VRMS=14.3mV
d=∆VRMS/VRMS,avg=10.83%
Meas. time period 2.5min
Output voltage at 100g mass loading, where
samples are the number of scanned and
recorded voltage values, corresponding to
vibrational cycles.
2
D
1
D 2
C
+
–
+
1
C
)
(t
vp B
V CAP
V
Super capacitor
+
–
p
I
p
C
PEH equivalent
electronic circuit
– (+)
+ (–)
p
r
p
C
i
1
D
i
2
D
i
out
in
Designed interface circuits for converting
the energy from the micro-power PENGs
based on passive voltage doubler and quad-
rupler with Schottky diodes for
supercapacitor charge.
1
D
1
C
p
I
p
C
PEH equivalent
electronic circuit
– (+)
+ (–)
2
D
2
C
3
D
3
C
4
D
in
)
(t
vp
B
V CAP
V
Super capacitor
+
–
out
4
C
+
–
Measured
voltage from a
single PENG on
a micro super-
capacitor
12. 28-29-Apr-21
12
• Perovskites solar energy harvesting and sensing elements – materials
selection, technology aspect, signal processing.
200 300 400 500 600 700
0
20
40
60
80
100
GZO
ITO/GZO
ITO/GZO1
ITO/GZO2
Transmittance,
%
Wavelength, nm
0.8 1.2 1.6 2.0 2.4
10
20
30
40
50
60
70
80
90
100
ITO/GZO2
ITO/GZO1
ITO/GZO
GZO
Reflectance,
%
Wavelength, m
E, eV
3
4
5
6
4.3
ITO
4.4
4.23
GZO
GZO2
CdS/ZnS
QD
perovskite
3.9
6
4.1
Al
3.8
5.3
Optical filtration by bilayer nanocoatings ITO/ZnO:Ga2O3 (GZO) – transmits
the visible light and rejects UV and near-to-middle IR range
Low light scattering (ITO/GZO has a surface roughness of 7.1 nm), tuning of the energy level
alignment to the most widely used sulfite based quantum dots and power produced.
250 500 750 1000 1250 1500
0
1
2
3
4
5
6
7
red light
green light
blue light
Power,
W
Intensity, cd/m
2
13. 28-29-Apr-21 13
0 2 4 6 8 10 12 14
0
50
100
150
200
250
300
white
blue
green
yellow
red
white
t, min
V,
mV
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
I,
A
2.16 2.18 2.20 2.22 2.24 2.26 2.28 2.30 2.32 2.34 2.36
0
50
100
150
200
250
300 Vmax = 291.9 mV
10%.Vmax
90%.Vmax
30 ms
trise
light
dark
t, s
V,
mV
0.0
0.4
0.8
1.2
1.6
I,
A
AN231K04-DVLP3
development system
Value of the output
voltage from TIA – vo
Differential
amplifier
PWM signal – vPW M(t)
FPAA configuration in
ANADIGM DESIGNER 2
program
Sawtooth signal – ϴ(t)
Photodetector
USB interfaces to
AN231K04-DVLP3
and VC 820
CdTe/perovskte/CsBr-based quantum dots photodetector device,
spectral response, response time, FPAA mixed-signal processing circuit
and photodetector signals.
Thickness of the active layers ~550 nm in total, cell’s active area - 2.25 cm2.
14. 28-29-Apr-21 14
1
D
2
D
in
v
SC
V
Supercapacitor
+
–
+
–
1
1’
1
R
out
v
+
–
2
2’
CH
I
L
R
Solar Energy
Harvester Cells
+
i
r
F
in
i out
i
in
v
Solar Energy
Harvester Cells
Power management
system based on
boost regulator
SC
v
L
R
in1
in2 out1
back_up
+
–
BAT
V'
Primary
battery
Micro
supercapacitor
bat
+
–
System
load
out
V
GND
out2
+
i
r
in
i BAT
i
F
24 26 28 30
470
475
480
485
490
495
500
505
temperature,
o
C
voltage,
mV
V0
0
5
10
15
20
25
30
L = 5000 cd/m
2
voltage
variation,
mV
V0
0 40 80 120 160
0
50
100
150
200
250
300
red light
blue light
white light
supercapacitor
voltage,
mV
charging time, min
Stable bromide-based lead-free perovskite solar cell, different possible power management
systems (monolithic and discrete) intended for low-power solar energy harvesting devices,
output voltage variation with the temperature and supercapacitor charging curve at
different spectral response of the cell.
15. 28-29-Apr-21 15
• Future work
- Development of implantable fully organic piezoelectric energy
harvesting/sensing elements.
- Optimization of the layers interface conditions to increase the energy
conversion efficiency at both types of devices (piezoelectric and solar).
- Impedance study for extraction of parasitic components, minimizing
the energy losses and maximizing the impedance matching.
These studies are related to 2 National and 3 International projects
that are currently running in the group (3 of them are coordinated
from Dr. Mariya Aleksandrova and 2 are coordinated from Dr. Georgi
Dobrikov).
16. Additional research activities:
NATIONAL CENTER OF MECHATRONICS AND CLEAN TECHNOLOGY
Operational Program: Science and Education for Smart Growth 2014-2020
LABORATORY
“Micro/nanoassembling and micropackaging”
Coordinated from Dr. V. Videkov and Dr. S. Andreev
The activity of the laboratory is focused on assembly and micropackaging of microelements
(semiconductor crystals, MEMS structures, chip sensors, etc.) in micromodules. The main
problems that can be solved are:
Placing microelements on rigid and flexible planar substrates;
Soldering crystals on various metallized substrates by conductive soldering with high precision;
Metallizing of variety of substrates for the needs of the mounting and assembling;
Placing elements by the technology of inverted mounting;
Application of nanomaterials and elements in the mounting process.
16
28-29-Apr-21
17. Thanks to my collaborators from the Faculty!
Prof. Dr. Valentin Videkov
Assoc. Prof. Dr. Georgi Dobrikov,
Assoc. Prof. Dr. Svetozar Andreev
Assoc. Prof. Dr. Krassimir Denishev
Assoc. Prof DSc. Ivailo Pandiev
Assoc. Prof. Dr. Boriana Tzaneva
Dr. Georgi Kolev
PhD Student Tsvetozar Tsanev
In addition thanks to our partners from
Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Science (BAS)
Institute of Optical Materials and Technology, BAS
University of Bielefeld, Germany
Technische Universität Dresden, Germany
Lakehead University, Canada
Western-Caucasus Research Center, Russia
Institute of Nanoscience and Nanotechnology, NCSR "Demokritos“, Greece
Istanbul Techical University, Turkey
Universidad Tecnológica Metropolitana, Santiago, Chile
Govt.V.Y.T.PG. Autonomous College Durg, India
University of Pune, India
Biosciences and Biotechnology Research Center, Indonesia
Holistic Electronics Research Laboratory, University of Cyprus, Cyprus
17
18. 28-29-Apr-21
18
List of relevant publications authored by our group in 2020-2021:
M Aleksandrova, T Tsanev, A Gupta, AK Singh, G Dobrikov, V Videkov, Sensing Ability of Ferroelectric Oxide
Nanowires Grown in Templates of Nanopores, Materials , 13 (7), 1777, 2020.
M. Aleksandrova, T. Ivanova, S. Koch, F. Hamelmann, D. Karashanova, K. Gesheva, Study of Sputtered Barium
Strontium Titanate Films for Energy Harvesting Applications, Advanced Materials Letters, Vol. 11, no 10,
20101567, 2020.
M.P.Aleksandrova, T.D.Tsanev, I.M.Pandiev, G.H.Dobrikov, Study of piezoelectric behaviour of sputtered
KNbO3 nanocoatings for flexible energy harvesting, Energy, Vol. 205, 2020, 118068.
Mariya Aleksandrova, Polymeric seed layer as a simple approach for nanostructuring of Ga-doped ZnO films
for flexible piezoelectric energy harvesting, Microelectronics Engineering, Vol. 233, 15, 2020, 111434.
M. P. Aleksandrova, G. D. Kolev, R.Tomov, A. K. Singh, K. C. Mohite, G.H.Dobrikov, Role of the CdS/ZnS
core/shell quantum dots in the thin film lead-free perovskite solar cells, Bulgarian Chemical
Communication, Special Issue C, vol. 52, pp. 65-71, 2020
A. Hashmi, B. Jain, J. Singh, M. Aleksandrova, Aj.K.Singh, Facile Synthesis of Bismuth-Based Perovskite and
Solvent Engineering for Improving the Crystallinity of Lead-Free Perovskite Material: A Microstructural
Exploration, 6th IEEE International Conference on Environment-Friendly Energies and Applications, Sofia,
Bulgaria, March 24-26, 2021
Mariya Aleksandrova, Ivailo Pandiev, Impedance Spectroscopy of Lead-Free Ferroelectric, Coatings, 11, 221,
2021
I Pandiev, M Aleksandrova, G Kolev, Design and Implementation of Interface Circuits Intended for Printed
Piezoelectric Micropower Harvesters on Flexible Substrates, 5th International Conference on Energy
Engineering and Smart Materials Barcelona, Spain, April 15-17, 2020, IOP Conf. Ser.: Mater. Sci. Eng., 876,
012007, 2020.
