The document discusses sustainable energy sources and nanomaterials for sustainable development applications. It provides an overview of solar energy and chalcogenide-based solar cells. Research on developing nanostructured metal-doped chalcogenides and tellurides for multifunctional applications such as solar cells and optical/electrical devices is summarized. Synthesis methods for producing semiconductor nanocrystals and nanosheets are described. Characterization shows the materials have tunable properties like optical bandgap dependent on size, composition and doping.

1. National Seminar on “Recent Trends in Science for
Sustainable Developments”
Dr Ramakanta Naik
Associate Professor
ICT-IOC Bhubaneswar 1
Nanostructured Metal doped
Chalcogenides for Multifunctional
Applications
GIET University, GUNUPUR, 21.04.2023

2. Plan of talk
➢Introduction
➢Sustainable Energy Sources
➢Solar Energy
➢Chalcogenide based Solar cell
➢Other sustainable energy sources
➢Our Research towards Sustainability
➢Summary
2

3. 3
Sustainable
Development
Development that meets the
needs of the present, without
compromising the ability of
future generations to meet their
own needs

4. Goals to achieve through Sustainable Development
4
❑No Poverty, Zero Hunger, Good
Health and Well-being
❑Affordable and Clean Energy
❑Sustainable Cities and
Communities
❑ Climate Action
❑ Life Below Water
❑ Life on Land
❑Reduced Inequalities
❑Responsible Consumption and
Production
❑Clean water and sanitation

5. Sustainable Energy Sources
Renewable energy sources
➢Solar Energy
➢Wind Energy
➢ Bioenergy (organic matter
burned as a fuel)
➢Hydroelectric, including
tidal energy.
5

6. 6
Solar Energy
▪ A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into
electricity by the photovoltaic effect, which is a physical and chemical phenomenon.
▪ Various types of materials, used for solar cell applications-such as silicon based, perovskite based,
chalcogenide based or organic solar cells.
Fourth generation, also known as “inorganics-in-organics,” combines
the low cost/flexibility of polymer thin films with the durability of
innovative inorganic nanostructures

7. Chalcogenide Materials
Chalcogenide materials
❑ Group VI elements
❑ Semiconducting nature
❑ Compositional dependency
❑ Transparency over Visible to IR range
❑ Greater polarizability
➢ Amorphous P-type Semiconductor
➢ Optical non linearity
➢ High photosensitivity
➢ Sensitive to band gap light

8. Optical data storage
Optical fibre

9. 9
Chalcogenide Thin Films for Solar Cell Applications
▪ Various IV-VI compounds (SnSe, SnS, GeS,
GeSe) are serves as good solar cell materials
for future applications.
▪ The optoelectronics properties of like
indirect and direct bandgaps of these
material ranges between 1.2-1.5 eV. For
this it is used as single-junction solar cells.
▪ GeSe is a favourable photo-absorber for its
excellent electrical and optical properties.
▪ The efficiency of these materials shows
14.8%.
▪ To increase the efficiency and carrier
collection efficiency, various structural
changes has been adopted.

10. 10
Ternary Quasi-2D chalcogenide based Solar cell material
➢2D CuSbX2 (X=S, Se) shows
chalcostibite crystal structures.
➢CuSbX2 considered as a potential
photovoltaic material due to its optical
bandgap.
➢CuSbS2 – 1.38-1.55 eV and CuSbSe2 –
1.1 eV.
➢Show absorption coefficient in the
visible region >104 cm-1 and >105 cm-1
for CuSbS2 and CuSbSe2, respectively.
➢Exhibit excellent physico-chemical
stability and mostly behaves as p-type
semiconducting behaviour.
➢Power conversion efficiency (PCE) is
more for CuSbS2 than CuSbSe2 material.

11. 11
Chalcogenide Perovskites for Photovoltaic application
➢Chalcogenide based perovskite
exhibit photo-absorbers.
➢CaZrSe3, SrZrSe3 etc. show
suitable bandgap around 1.2-1.5
eV.
Perovskite: ABX3, where 'A' and 'B' represent
cations and X is an anion that bonds to both:

12. 12
Other Sustainable energy applications
➢ Various storage cell are used to
replaces fossil fuel devices.
➢ Different types of batteries such as
Li-ion, Na-ions, K-ion are now in
the lime-light of research.
➢ Similarly, other alternate energy
sources like H2 evolution,
electrocatalytic reaction are
considered as green chemistry for
earth.
➢ Choice of materials and techniques
are crucial for this.

13. Our Research on Nanomaterial based compounds
13
Nanomaterials
Based on
material
Carbon-
based
Inorganic-
based
Organic-based
Composite-
based
Based on
dimension
0 D
1 D
2 D
3 D
Based on
origin
Natural
Synthetic
(engineered)
Nanomaterials are usually considered to be materials with at least one external dimension that
measures 100 nanometres or less or with internal structures measuring 100 nm or less.

14. Nanomaterials based on material types
❑Carbon-based nanomaterials
▪ Morphological form: hollow tubes,
ellipsoids or spheres.
▪ Example: Fullerenes (C60), carbon
nanotubes (CNTs), carbon nanofibers,
carbon black, graphene (Gr)
▪ Production methods: Laser ablation,
Arc discharge, and Chemical vapor
deposition (CVD)
❑Inorganic-based nanomaterials
▪ Includes: metal and metal oxide
▪ Synthesized into: metals (Au or Ag
NPs), metal oxides (TiO2 and ZnO
NPs, semiconductors (silicon and
ceramics 14
❑ Organic-based nanomaterials
▪ Utilization of non-covalent (weak)
interactions for the self-assembly and
design of molecules helps to transform
the organic NMs into desired structures
such as dendrimers, micelles, liposomes
and polymer NPs.
❑ Composite-based nanomaterials
▪ Multiphase NMs: one phase on the
nanoscale dimension that can either
combine NPs with other NPs or NPs
combined with larger or with bulk-type
materials. i.e., hybrid nanofibers,
metalorganic frameworks

15. 15
❑Natural Nanomaterials:
▪Produced in nature either by biological
species or through anthropogenic
activities
▪Sources: forest fires, volcanic ash,
ocean spray, and the radioactive decay
of radon gas, weathering processes of
metal- or anion-containing rocks, acid
mine drainage sites etc.
❑Synthetic (engineered) Nanomaterials:
▪Produced by mechanical grinding,
engine exhaust and smoke,
▪Synthesized by physical, chemical,
biological or hybrid methods.

16. 16

17. 17
Bulk Nanomaterials
Ratio of h and d determine the shape of nanoparticle
High surface area of nanomaterial for given volume
• Physical and chemical properties of
nanomaterials are closely related on size
and shape of nanomaterials.
• Nanomaterials have high percentage of
surface atoms as compared to bulk
• Nanomaterials also exhibited shape
dependent properties that are useful for
applications such as catalysis, data storage,
optics.
• The study of shape dependent properties is
quite complex.
• Reduction of size affects various properties
such as melting point, bandgap, reactivity,
mechanical properties, optical properties,
magnetic properties, electrical and
electronic properties.
Shape and size dependent properties

18. 18
Melting point of gold nanoparticles reduced as particle size decreased to 5 nm
Melting point

19. Importance of “Nanomaterials
❑Showcases unusual
mechanical, electrical, optical
and magnetic properties
essential for many industrial
applications.
▪ Nanophase ceramics are more
ductile at elevated temperature
compared to the coarse-
grained ceramics.
▪ Shows various non-linear
optical properties
▪ Semiconductor Q-particles
shows quantum confinement
effect which may lead to the
properties like, luminescence
in Silicon powders.
▪ Germanium quantum dots as
infrared optoelectronic
devices.
Industries dependable on nanomaterials

20. Physical Methods
▪ Thermal Evaporation
▪ Ball Milling
▪ Electron Beam Evaporation
▪ Laser Ablation
▪ Electro-spraying
Chemical Methods
• Sol-gel synthesis
• Hydrothermal synthesis
• Chemical vapor deposition
(CVD)
• Colloidal Synthesis
• Co-precipitation method
20
Material Preparation

21. Synthesis methodologies of nanomaterials

22. 22
Se Based Nanomaterials
Selenium
❑ High glass-forming ability
❑ Higher refractive index
❑ High photosensitivity, polarizability
❑ Excellent transmission over infrared regions
Solutions
Selenium
Bi
Zn
Cu
In Ga
Selenium Limitations

23. Quantum dots
❑ Nanoscale crystal having size
(diameter ~ 2-10 nm, comprising 10-50
atoms)
❑ Semiconducting material
❑ Highly fluorescent
❑ QDs can produce distinctive colours
determined by the size of the
particles.
❑ Quantum confinement due to limited
number of atoms
❖ Depending on the number of atoms,
the band gap changes by changing the
fluorescence.
❖ Quantum confinement of nanoscale
level depending on the size.
❖ Smaller size → larger band gap →
higher frequency → lower wavelength
→ emitting blue/violet color
23
Nanosheets embedded ZnSe/Bi2Se3 core/shell quantum dots
for the optical and antibacterial activity
Quantum dots (QDs)
❑ Modifies properties
❑ Enhances the functionality, stability and
dispersibility
❑ Protection of core
❑ Improve the chemical stability
Importance of core-shell
P.Priyadarshini et al. Surf. Int. 37 (2023) 102687

24. 24
❖ Synthesis of different water dispersed ZnSe/Bi2Se3 core/shell
quantum dots by using the cation exchange method.
Mn+(liquid) + C–A(crystal) → C+(liquid) + Mn–A(crystal)
S1 S5
Varying Bi concentration
❑Showed typical type-II band alignment,
❑ Carriers (holes/electrons) localized at different region
❑Very low recombination rate
❑Temperature equilibrium between carriers and the crystal.
Why ZnSe/Bi2Se3 QDs ?

25. ➢ Existence of ZnSe cubic phase.
➢ Unreacted selenium presence showed Se phases.
➢ Substantial peak become broader.
➢ Change in vibrational level
observed.
➢ Appearance of Bi2Se3 bond
vibration.
❑ Quantum dot embedded in the nanosheet.
❑ Average QDs sizes are 2-3 nm range.
❑ Diffraction fringes corresponds to the ZnSe
(111) plane.
❑ SEAD pattern confirmed for Se[101] and ZnSe
[111] planes.

26. With shell thickness
increase, average
thickness of the
nanosheets enhanced
❑ Confirms the
presence of Zn,
Se, and Bi in the
material.
❑ Uniform
distribution of
all elements
throughout the
sample.
S1 S3 S5
S1
S3

27. 27

28. 28
300 450 600 750 900 1050 1200
0.08
0.16
0.24
0.32
Absorbance
l (nm)
S1
S2
S3
S4
S5
1.0 1.5 2.0 2.5 3.0 3.5 4.0
(ahn)
2
(cm
-1
eV)
2
hn (eV)
S1
S2
S3
S4
S5
Optical
bandgap
S1 S2 S3 S4 S5
(Eg) in eV 2.62 2.56 2.45 2.38 1.57
❖ Absorbance improvement with an increase in the Bi content.
❖ Result due to the enhancement in the size of the QDs.
❖ PL spectra for 325 nm excitations
❖ Peak position at ~ 600 nm.
❖ No shift in PL emission spectra observed.
400 500 600 700 800
Normalised
PL
intensity
(a.u.)
l (nm)
S5
S4
S3
S2
S1
400 500 600 700 800
Normalized
PL
intensity
ZnSe/Bi2Se3

29. • Antibacterial activity increased with
concentration.
• Good activity against Staphylococcus
aureus (ATCC 25923) only.
• Staphylococcus aureus (ATCC
25923) and Pseudomonas
aeruginosa (ATCC 27853) were
chosen.
• Bacterial strains were revived, and
fresh culture was prepared.
• Nanoparticles solutions of different
concentrations used.
• Plates were then incubated at 37°C
for 24hrs.
Antibacterial activity
Culture preparation
Antibacterial response

30. 30
Zn doping induced optimization of optical and dielectric characteristics
of CuInSe2 nanosheets for optoelectronic device applications
❑ Well known chalcopyrite system
❑ Semiconducting nature
❑ Small direct bandgap
❑ High absorption coefficient
❑ High stability
❑ Compositional dependent properties
Importance of CuInSe2 Synthesis procedure
Why Zn doping ?
❖ Facilitates the alteration of defects in the
semiconductor crystal lattice.
❖ Extends the photoresponsivity toward the visible
light radiation.
❖ Zn as donor dopant enhances carrier concentration.
❖ Improves thermoelectric and absorption capability. P.Priyadarshini et al.Journal of Alloys and Compounds,945 (2023)169222

31. 31
❑ Observed tetragonal CuInSe2 pure
phase.
❑ Increment in lattice disorder and defects
with Zn doping.
❑ Raman peak at 177 cm-1 and 214 cm-1
from A1 and B2 mode of CuInSe2 phase.
❑ 124 cm-1 peak from single phase of the
CIS.
❑ TEM fringes confirms tetragonal CuInSe2
(112 ) phase.

32. 32
CIS ZCIS-1 ZCIS-2 ZCIS-3
ZCIS-2
ZCIS-2
Morphology changed from clean nanosheets to pigmented nanosheets.
❑ Confirms the presence of Cu, In, Zn and Se elements.
❑ Appearance of the Zn XPS peak in ZCIS-3 confirms the Zn doping.

33. 33
❑ Absorbance enhanced with the Zn doping.
❑ Enhanced trap state density over gap
region by creating more defects.
❑ Emission band shifted to higher
wavelength.
❑ Deconvoluted PL spectra contains peaks
corresponds to point defects.

34. 34
50 100 150 200 250 300 350 400
0
1x108
2x108
3x108
4x108
5x108
6x108
7x108
8x108
1 kHz
10 kHz
50 kHz
100 kHz
1 MHz
e
r
Temperature (o
C)
50 100 150 200 250 300 350 400
0
70
140
210
280
350
420
tan
d
Temperature (o
C)
1 kHz
10 kHz
50 kHz
100 kHz
1 MHz
0 200 400 600 800 100
0
5
10
15
20
25
RT
100O
C
200O
C
300O
C
400O
C
tan
d
Frequency (kHz)
❑ Higher dielectric constant at low frequencies attributed to interfacial/space
polarization.
❑ Peak presents phase transformation behavior.
❑ At low temperatures, charge carriers show weak response.
❑ High temperature provides enough excitation thermal energy orient.
Thus, the polarization improves, and the dielectric behavior improves.

35. 35
Te Based Nanomaterials
Tellurium
❑ High polarizability
❑ Larger non-linear optical properties
❑ Thermoconductive Properties
Te
+
Zn, Cu, Bi, Mn & V
❑Greater solubility
❑Tuneable optical bandgap
❑Reduces toxicity
❑Enhanced storage ability
❑Shift in the absorption edge

36. 36
❑ Zinc telluride (ZnTe) an important class semiconductor
nanocrystals.
❑ Showed wide band gap of ranges between 2.3 eV.
❑ Well known solar cell applicant.
Colloidal method
❑ Traditional method of synthesizing inorganic nanocrystals,
including semiconductors and metals.
❑ Different precursor prepared for the nanocrystal synthesis.
❑ Easy fabrication
❑ Greater mobility
❑ Superior electrical and optical properties.
❑ Applications : transistors, diodes, photodetectors
Templet-free one-pot synthesis of Bi-doped ZnTe nanoflowers by cation
exchange method for optoelectronic applications and antibacterial
activity
Importance of 2D Materials
Synthesis procedure
S. Das et al. Journal of Alloys and Compounds (2023)

37. 37
❑ ZnTe and Te hexagonal phases are observed.
❑ The Raman spectra found between the 120-140 cm-1 exhibit the existence of Te-rich
phases in the ZnTe NS.
❑ The bands at 126 and 141 cm-1 represent the A1 and E vibrational mode of Te,
respectively.
❑ The peak appeared at 643 cm -1 is due to vibrational modes of the ZnTe phase.
❑ Fringes corresponds to ZnTe (200) peak.

38. 38
❑ Nanosheets accumulated to form flowers.
❑ Confirms presence of Bi, Zn and Te elements.
❑ XPS study of the material, shows the +2 oxidation
state of Zn and +2 oxidation state of Te.
❑ Change in the intensity of Bi peak shows the
presence of larger Bi content.

39. 39
❑The absorption edge showed blue shift.
❑Incorporating Bi increased the material's disorder and increases localized states
over gap region.
❑Each PL emission peak contains 3 gaussian peaks corresponds to Zn vacancies
and Bi interstitial defects.

40. 40
❑ Zn is the most abundant and its related compounds have higher bioactivity.
❑ Bi has better biocompatibility properties.
❑ Antibacterial activity of BZT-1 nanosheets Staphylococcus aureus (ATCC 25923) and Pseudomonas
aeruginosa (ATCC 27853).
❑ Significant antibacterial activity against both bacterial strains.
❑ Suitable for biological applications.

41. 41
Synthesis of CuSe1+xTe1-x nanostructures by microwave method for
optoelectronic and dielectric application
❑ Reaction rate acceleration
❑ Short reaction time
❑ Versatility of applied reaction conditions
❑ Higher yields
❑ Selective heating
❑ Excellent reproducibility
❑ Easy handling
Microwave Synthesis
Importance of Cu-Se
❑ Ability to form various stoichiometric and
nonstoichiometric compounds.
❑ Cu7Se4, Cu3Se2, CuSe - orthorhombic, cubic,
hexagonal.
Importance of Cu-Te
❑ P-type semiconductor
❑ Attractive for thermoelectric application and ionic
conductivity.
❑ Known to exist in a wide range of compositions and
phases.
S. Das et al. ACS Applied Nano Materials. (2023)

42. 42
❑ The peak at 135 cm−1 confirms
the Cu-Te Ag vibrational mode.
❑ The low-intensity 112 cm−1
peak refers to the A2 mode of
hexagonal Se.
❑ Prominent peak appeared at
165 cm−1 representing the
Te−Te homopolar bond.
❑ The detected peak around 415
cm−1 corresponds to the
longitudinal mode of CuSe
present in the nanostructure.

43. 43
CST-3
❑ Morphology changed from nanosheets to nano sphere with
variation in Se/Te content.
❑ Confirms Cu, Se, Te element presence.
❑ XPS peak confirms the presence of both Cu2+ and Cu1+ oxidation
states in the material.
❑ Satellite peak represents the Cu0 and Cu1+ states.
❑ Intensity variation in the Se and Te peak shows the concentration
ratio of each elements.
CST-1
CST-5
CST-2
CST-4

44. 44
❑ Absorbance exhibit a blue shift.
❑ Bandgap varies from 2.73 eV to 3.01 eV with Se/Te concentration.
❑ Morphology tunned physical property of the material.
❑ PL emission peak centered at 650 nm.
❑ Deconvolution contains three peaks corresponds to point defects.

45. 45
Temperature response of dielectric parameters Photo-response of CST-3
❑ Increase in temperature increased the dielectric constant at lower frequency
region.
❑ A.C. conductivity improved with frequency.
❑ The light current (7.5 nA) gradually decreased than the dark (8.15 nA) one.

46. 46
Second approach: Physical Vapour Deposition

47. 47
Bilayered and composite based metal selenide thin films
In2Se3 applicant in diodes, photodetectors,
photovoltaics.
❑ Direct band gap semiconductor
❑ Application as absorber layer in PV.
Bi2Se3one of the top performing thermoelectric
materials
❑ Greater electrical conductivity
❑ Large seeback coefficient
❑ Low thermal conductivity at room temp.
P.Priyadarshini et al.
J. Am. Ceram. Soc. 104 (11) (2021) 5803
P.Priyadarshini et al.
J. Appl. Phys. 129 (2021) 223101

48. 48
❑ Phase transformation upon
annealing and laser
irradiation.
❑ In-Se, ϒ-In2Se3 , Se-Se, Bi2Se3
vibrational mode observed.
❑ Crystallites appeared in
annealed and irradiated films.
❑ Elemental peaks observed in
EDX spectra.
Bi
Se
In
Se
In
In
In

49. 49
Eg = 1.29 eV Eg = 1.09 eV
Eg = 1.11 eV Eg = 1.23 eV
Eg = 1.68 eV Eg = 1.30 eV
Eg = 1.55 eV
Eg = 1.58 eV
Indirect transition
Direct transition
𝜶𝒉𝒗 = 𝑩 𝒉𝒗 − 𝑬𝒈
𝑶𝒑𝒕 𝒎
Tauc relation
α=Absorbance/thickness
absorption coefficient (α)
❑ Increase in absorption power with
increase in incident energy.
• Bi deposition into In2Se3 host matrix
reduced transmission.
• Transmission increased with annealing
(38%) and irradiation (29%).
❑ Bi layering creates more defect states
over gap region.
❑ Annealing and irradiation reduced
defect states and increased structural
ordering.

50. 50
Urbach energy
❑ Absorption edge is classified into three regions
▪ weak absorption region, Urbach region, and
Tauc region.
❑ The Urbach region (α < 104 cm-1) and Tauc regions (α >
104 cm-1)
❑ Urbach tail → photon absorption among localized tail
states and extended band states.
𝜶 = 𝜶𝟎𝒆
𝒉𝒗
𝑬𝒖 ⇒ 𝒍𝒏𝜶 = 𝒍𝒏𝜶𝟎 +
𝒉𝒗
𝑬𝒖
❑ Urbach energy increased with Bi incorporation while
annealing and irradiation reduced Eu.

51. 51
𝒏2
− 1 =
𝑬0𝑬𝒅
𝑬0
2
− 𝒉𝝑 2
Moss rule i.e., Egn4~ constant
𝒌 =
𝜶𝝀
𝟒𝝅
❑ complex refractive index ෥
𝒏 = 𝒏 + 𝒊𝒌
❑ n relates velocity of light and k relates
deterioration of incident beam.
❑ Refractive index calculated by
Swanepoel method.
❑ Satisfies Moss rule.
❑ Dispersive nature of ‘’n’’ observed
through Wemple Di-Dominico model.
❑ Increase in interband and transition.
❑ More interaction of atoms.
𝒏 = [ 𝑵 + 𝑵𝟐
− 𝒔𝟐
𝟏
𝟐 ]𝟏/𝟐
where 𝑵 = 𝟐𝒔
𝑻𝑴−𝑻𝒎
𝑻𝒎𝑻𝑴
+
𝒔𝟐+𝟏
𝟐
Swanepoel envelope method

52. 𝝈𝒐𝒑𝒕 =
𝜶𝒏𝒄
𝟒𝝅
, 𝝈𝒆𝒍𝒆𝒄 =
𝝀𝒏𝒄
𝟐𝝅
❑ The electrical and optical conductivity of bilayer film is
much higher.
❑ Annealing and irradiation allow both layer to diffuse.
❑ Change in structural level affects the conductivity.
❑ Non-linear response of material comes into action with high
intensity of incident beam.
❑ Applied in optical switching, telecommunication fibre,
Signal processing devices.
❑ Polarization, 𝑷 = 𝝐𝟎[𝝌 𝟏
. 𝑬 + 𝝌 𝟐
. 𝑬𝟐
+ 𝝌 𝟑
. 𝑬𝟑
+ ⋯ ]
1st order linear susceptibility =
𝒏𝒐
𝟐−𝟏`
𝟒𝝅
3rd order non-linear susceptibility =𝑨
𝒏𝒐
𝟐−𝟏`
𝟒𝝅
𝟒
❑ Change in R.I. due to nonlinear response, Δn = n2 𝑬 𝟐
Non-linear refractive index = 𝐧𝟐 =
𝟏𝟐𝛑𝛘 𝟑
𝐧𝐨
Non-linear
response
In2Se3 Bi/In2Se3 Annealed Irradiated
χ (1) 0.731 1.824 1.213 1.058
χ (3) x10-10 0.48.5 18.81 3.68 2.13
n2 x10-9 0.566 14.4 3.4 2.12

53. 53
100 150 200 250 300
200
300
400
500
600
Intensity
(a.u)
Raman shift (cm-1
)
In35Se65
Bi5In30Se65
Bi7In28Se65
Bi10In25Se65
Bi15In20Se65
127
170
249
148
232
123
192
Structural and morphological study of BixIn35-xSe65 film
❖ Showed polycrystalline nature.
❖ Appearance/disappearance of crystalline peaks related to lattice
expansion and grain stacking arrangement.
❖ In-Se, Se-Se, Bi2Se3 bond vibrations observed.
❖ Homogeneity and Uniformity in prepared films.

54. 54
600 700 800 900 1000 1100
2
4
6
8
10
a
x
10
4
(
cm
-1
)
Wavelength (nm)
In35Se65
Bi5In30Se65
Bi7In28Se65
Bi10In25Se65
Bi15In20Se65
0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
0
100
200
300
400
500
(ahv)
1/2
(eV
cm
-1
)
1/2
Energy (eV)
In35Se65
Bi5In30Se65
Bi7In28Se65
Bi10In25Se65
Bi15In20Se65
1.20 1.35 1.50 1.65 1.80 1.95 2.10
0
1x1010
2x1010
3x1010
4x1010
5x1010
6x1010
In35Se65
Bi5In30Se65
Bi7In28Se65
Bi10In25Se65
Bi15In20Se65
(ahv)
2
(eV
cm
-1
)
2
Energy (eV)
❑ Transmittance reduced.
❑ Red shift in absorption edge.
❑ Absorption coefficient,
𝜶 =
𝟏
𝒅
𝒍𝒏
𝟏−𝑹 𝟐
𝟐𝑻
+
𝟏−𝑹 𝟒
𝟒𝑻𝟐 + 𝑹𝟐
❑ Potential for absorbing layer
application.
Tauc relation, 𝜶𝒉𝒗 = 𝑩 (𝒉𝒗 − 𝑬𝒈)𝒑
❑ Direct and indirect Eg reduced with Bi
doping.
❑ Density state model by Mott and Davis
explains the increase in defects.
❑ Formation of unsaturated and
dangling bonds reduces Eg.

55. 55
0 2 4 6 8 10 12 14 16
0.7
0.8
0.9
1.0
1.1
1.2
1.3
Eg
Ind
c(3)
Bi at %
E
g
Ind
(eV)
0.3
0.6
0.9
1.2
1.5
1.8
c
(
3
)
x
10
-10
(esu)
600 700 800 900 1000 1100
1.5
3.0
4.5
6.0
7.5
9.0
Optical
density
(OD)
l (nm)
In35Se65
Bi5In30Se65
Bi7In28Se65
Bi10In25Se65
Bi15In20Se65
1.2 1.4 1.6 1.8 2.0
0.2
0.4
0.6
0.8
1.0
1.2
Skin
depth
(d
x
10
-4
)
cm
Energy (eV)
In35Se65
Bi5In30Se65
Bi7In28Se65
Bi10In25Se65
Bi15In20Se65
❑ OD relates absorption of incident
radiation through distance.
𝑶𝒑𝒕𝒊𝒄𝒂𝒍 𝒅𝒆𝒏𝒔𝒊𝒕𝒚 = 𝜶 𝒙 𝐭
❑ OD reduced with λ and get
saturated.
❑ Skin depth, 𝜹 =
𝟏
𝜶
❑ It reduced with Bi%.
❑ Increase in non-linearity.
❑ Greater χ(3) infers higher
absorption power.
❑ Potential for optical switching
and non-linear devices.

56. 56
❑ZnSe/Bi2Se3 QDs with different shell thickness provide more stability and
improved absorption capability.
❑The antibacterial activity against Staphylococcus aureus (ATCC 25923) and
Pseudomonas aeruginosa (ATCC 27853) , which facilitates the path for
biomedical applications.
❑The Zn doping in CuInSe2 nanosheets alters the morphological view and
improves the absorbing capability with reducing bandgap.
❑Conductivity and dielectric characteristics improved with Zn doping through
appearance of phase transition peak.
❑Bi alloying in CuInSe2 microrod flower reduced the optical bandgap due to
formation of more number of defects and disorder.
❑The photo response of CuBixIn1-xSe2 microrod flowers showed potentiality for
photo detector and photovoltaic applications.
Summary

57. 57
❑Bi-ZnTe NS exhibit increase in the width of the nanosheets with enhancement in
Bi concentration.
❑The BZT material shows good anti-bacterial activity against Staphylococcus
aureus (ATCC 25,923) and Pseudomonas aeruginosa (ATCC 27853) .
❑In CST nanostructures, with increase in the Se:Te ratio, the structural behavior
alters significantly, which leads to a gradual increase in crystallinity.
❑The dielectric study of the material prevails over the changes in the electrical
polarizability of the material significantly by varying both temperature and
frequency.
❑The photo-response study of the material enables it for potential photodetector
application.
❑Large atomic radius of Bi compared to In and Se induces enhancement in the
polarizability and thereby affects the non-linear response. Possible application :
Absorber layer in solar cell, optical switching and telecommunication

58. Conclusion
• The choice of suitable technique and
material plays a vital role in creating a
sustainable world.
• Both the chemical and physical
methods help to synthesis material
with less toxicity.
• Solar cell is one of the great
alternative, can be utilised for a
developing future.
• Other energy souces can also be
considered as a good alternatives
towards the hazardous energy
consumption.
58

59. Research Group
Dr. Subrata Senapati (Post. Doc Fellow)
Dr. Ramakanta Naik
Deviprasad Sahoo Priyanka Priyadarshini Subhashree Das Abinash
Parida
Biplab J. Jena Swikruti Supriya Prabhukrupa C. Kumar Sasmita Giri
Ph.D. Students

60. 60