After going through the literature review, it is understood that TiO2 is a high potential photoactive material. The doping of different metallic elements like Mg, Mn, Zr etc. decreases the band gap of TiO2 and place the material in a suitable range for photovoltaic application. Further studies reveal that TiO2 is a dye sensitive photocatalyst. In presence of different types of dye, photo absorption properties of TiO2 increases. In subsequent turn the optical properties of dye modified TiO2 shows enhanced properties in comparison to novice TiO2. Hence this attracts our attention to go for the study of the optical properties of dye modified TiO2. Another reason is that the dye that is chosen for the experiment is cost effective with better results as learned after the characterization. So, the present study has been undertaken for this project work.

1. Synthesis and Energy Harvesting in Dye-Sensitized TiO2 Photovoltaics
DEPARTMENT OF PHYSICS
VEER SURENDRA SAI UNIVERSITY OF TECHNOLOGY
BURLA, SAMBALPUR, PIN – 768018, ODISHA, INDIA
Master of Science In Applied Physics
By
Rashmirekha Barik (Regd. No.: 2007140005)
Under the Supervision of
Prof.(Dr.) Manas R. Panigrahi
1

2. PLAN OF TALK
 Introduction
 Literature Review
 Objective
 Experimental Procedure
 Results and Discussion
 Conclusion & Future scope

3.  General Introduction Of TiO2
3

4. Structure of TiO2
Anatase
 Tetragonal
 Band gap 3.2 eV
 Distortion of TiO2
octahedron is larger
Rutile
 Tetragonal
 Band gap 3.02 eV
 TiO2 octahedron is slightly
distorted
Brookite
 Orthorhombic
 Band gap 2.96 eV
 Has larger cell volume ,
least dense

5. Physics behind light absorption by TiO2
 TiO2 absorbs UV radiation from sunlight – produce pairs of electrons and holes
 Electron of VB becomes excited when illuminated by light
 Excess energy of this excited electron promote the electron to the CB
 Creation of negative-electron(e-) and positive-hole(h+) pair.
Stage is referred as the semiconductor’s
“photo-excitation” state
5

6. Band Gap of TiO2
Indirect band gap (a)Anatase,
direct band gap (b) Rutile
 In a direct band gap
semiconductor, the
maximum energy of
the VB and the
minimum of the CB
occur at the same
value of momentum.
 In an indirect band gap
semiconductor, the
maximum energy of the
VB and the minimum of
CB occurs at a different
value of momentum.

7.  Literature Review`
Visible light active TiO2 has been prepared by
 Metal doping(Cu, Co, Ni, Cr, Mn, Mo, Nb, V, Fe, Ru, Au, Ag, Pt)
 Nonmetal doping (N, S, C, B, F)
 Composites of TiO2 with semiconductors (Cd-S) having lower band gap
 Sensitization of TiO2 with dyes

8.  Objective
After going through the literature review, it is understood that TiO2 is a high potential photoactive material.
The doping of different metallic elements like Mg, Mn, Zr etc. decreases the band gap of TiO2 and place
the material in a suitable range for photovoltaic application. Further studies reveal that TiO2 is a dye
sensitive photocatalyst. In presence of different types of dye, photo absorption properties of TiO2 increases.
In subsequent turn the optical properties of dye modified TiO2 shows enhanced properties in comparison to
novice TiO2. Hence this attracts our attention to go for the study of the optical properties of dye modified
TiO2. Another reason is that the dye that is chosen for the experiment is cost effective with better results as
learned after the characterization. So, the present study has been undertaken for this project work.
8

9. 9

10. TiO2+Acetic Acid
Hydrolysis
TiO2 sol
0.1M HNO3 added
peptization
refluxing
TiO2 Gel
dried and grinded
powder TiO2
Dyes (MO, Beetroot,
KMnO4) addition
UV-VIS Spectroscopy
chracterization
Particle size Analysis
XRD Analysis
 Experiment
10

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X-ray diffraction
 Constructive interference of monochromatic X-rays from crystalline sample is the basis of X-ray diffraction. The interaction
rays create constructive interference when Bragg's Law is satisfied
2𝑑𝑠𝑖𝑛𝜃 = 𝑛𝜆 I =∣ F ∣2 mL − PA(θ)e−2M

12. 20 40 60 80
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Intensity
(A
U)
Position (degree)
TiO2
1
0
0
1
1
0
0
0
4
1
0
3
0
0
5
2
0
0
2
0
1
2
1
1
1
1
5
2
1
3
0
0
7
2
1
4
2
0
5
1
1
7
 XRD Analysis
• a: 3.35Ao, b: 3.35 Ao, c: 9.292 Ao , (JCPDS – 211272),
α=90o, β=90o, γ=120o with volume 104.48 Ao3, FOM 4.892,
chi square 1.0504.
• Tetragonal, space group I41/acd
• Anatase phase of TiO2
• Williamson-Hall method (W-H method)
βℎ𝑘𝑙 . 𝑐𝑜𝑠𝜃 =
𝐾𝜆
𝐷
+ 4ε . 𝑠𝑖𝑛𝜃
12

13. 20 30 40 50 60 70 80 90
30
40
50
position (2)
Crystallite
size
(nm)
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Microstrain(%)
Figure 3.3 Variation of crystallite size and strain with
position of TiO2
0.1 0.2 0.3
30
40
50
d-spacing(nm)
Crystallite
size(nm)
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Strain(%)
Figure 3.4: Variation of crystallite size and strain
with d-spacing
As the crystallite size decreases, the microstrain increases.
 Variation of crystallite size and strain
13

14. 14
 DLS instrumentation requires a laser light and a lens to converge
the light.
 Through the lens, the laser is made incident on the sample. The
scattered light is collected by a detector.
 This scattered light fluctuates due to Brownian motion. The
scattered light's intensity changes are translated into electrical
pulses.
 These pulses are fed into a digital correlator, which uses an
autocorrelation function to calculate particle size.
Particle Size Analyzer

15.  Particle Size Analysis
 The size of particle is analyzed by measuring particle’s Brownian
motion.
 The Brownian motion will be slower as the particle becomes
larger.
 Brownian Motion is monitored by DLS
15

16. 16
UV-Visible spectroscopy
 When a chemical compound absorbs light, some excitation and de-excitation processes of electrons occur in atoms
which result in the production of the distinct spectrum.
 when radiations interact with a chemical species, they can cause transition at different energy levels. The type of
transition depends upon the energy of the radiation.
𝐀 = 𝐥𝐨𝐠
𝑰𝑶
𝑰
= 𝐄𝐜𝐥

17. Absorption and Transmission spectra of TiO2 and dye (MO, Beetroot, KMnO4) sensitized TiO2
 UV-VIS Analysis
(a) Absorption and Transmission spectra
17

18. (b) Band Gap
 The optical bandgap is the limit at which
photons may be absorbed
 Tauc's relation
αhν = A hν − Eg s
 The optical band gap is determined as
the intercept along the x axis from the
graph (αhν)2
vs. photon energy (hν).
18

19. (c ) Urbach Energy
 An exponential increase in absorbance with energy
defines the Urbach Energy
 governed by the structural disorder and imperfection
 α E = αO exp
E−E1
Eu
 The urbach energy is estimated from ln(α) vs. (hν)
plot.
Eu =
1
slope

20. (d) Dispersion Energy & Oscillation Energy
 Sellmier relation
n2 − 1 =
EoEd
Eo
2
− (hν)2
 Plotting (𝑛2 − 1)−1 vs (ℎ𝜈)2 we can obtain
dispersion energy and oscillation energy. The
slope and intercept represent Eo and Ed
respectively.

21. CONCLUSION
 In this project TiO2 was prepared by modified sol gel method.
 The prepared sample was characterized by XRD for estimation of different structural
parameters.
 It is found that the prepared material is synthesized in pure anatase phase(tetragonal).
The lattice parameters obtained are a: 3.35Ao, b: 3.35 Ao, c: 9.292 Ao and α=90o,
β=90o, γ=120o .
 The absorbance and transmittance of different dyes (beetroot, MO, KMnO4)
sensitized TiO2 were obtained and optical properties were calculated.
 Out of the above 3 dyes under taken for study, beetroot modified TiO2 is observed to
be efficient in terms of band gap and other energy parameters in the studied range. 21

22.  FUTURE SCOPE OF WORK
In this project dye sensitized TiO2 has been prepared by modified sol gel technique and
different optical properties were studied. In future same material can be prepared using
different techniques keeping in mind its cost and ease of fabrication. Suitable material can
be chosen from the available natural and synthetic dyes. Their properties can be compared
with respect to efficiency and can be optimized for better use in the energy harvesting
sector.
22

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ACKNOWLEDGEMENT
I would like to thank every individual who helped and supported me in every step during this project work. I am highly indebted to
my supervisor Prof. (Dr.) Manas Ranjan Panigrahi for his scholastic guidance, prudent suggestion and constant supervision. I
would also like to express my profound gratitude to two other persons Mr. Abhilash Sahoo (Research Scholar) and Bhagya Shree
Biswal for their encouragement, valuable suggestion and constant help for this work.
I owe my heartfelt gratitude to my parents whose encouragement and blessing made it possible for me to complete the project.

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REFERENCES
 S. Chatterjee, I. B. Karki, “Effect of Photoanodes on the Performance of Dye-Sensitized Solar Cell”, Journal of the
Institute of Engineering,15,62-68 (2019)
 Wikipedia, https://en.wikipedia.org/wiki/Titanium_dioxide
 B. O’Regan, M. Grätzel, “High efficiency semiconductor based on dye sensitized colloidal TiO2 films”, Nature,
353, 737-740 (1991)
 M. Devi, M. R. Panigrahi, U. P. Singh. "Microstructures, optical and electrical properties of TiO2 thin films
prepared by unconventional sol–gel route", Journal of Materials Science: Materials in Electronics, 26, 1186-1191
(2014).
 K. S. Usha, R. Sivakumar, C. Sanjeeviraja, “Optical constants and dispersion energy parameters of NiO thin films
prepared by radio frequency magnetron sputtering technique”, Journal of Applied Physics, 114, 123501 (2013)

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THANK YOU