This document summarizes a seminar presentation on carbon nanotube based solar cells. It begins with an introduction to carbon nanotubes, describing their cylindrical nanostructure formed from graphene sheets rolled at specific angles. It then discusses properties of carbon nanotubes that make them suitable for solar cells, such as their electrical conductivity. The document reviews three generations of solar cell technology and their limitations before describing how carbon nanotubes can be incorporated into dye-sensitized solar cells as transparent electrodes, replacing conventional materials like ITO. It presents results showing a carbon nanotube-based solar cell achieved 7.04% efficiency compared to 7.34% for a standard platinum electrode cell. In conclusion, carbon nanotube electrodes

1. A
Seminar
On
“Carbon Nanotube Based Solar Cell”
Submitted to: Submitted By:
Supervisor Mohammad Safil Beg
Deepak Bhatia 14E2CNNTX3XP704
Assistant Professor
Centre of Nanotechnology
Rajasthan Technical University, Kota
December -2015


2. Carbon Nanotube Based Solar Cell

3. Outline
• Introduction
• Carbon Nanotubes
• Properties for CNTs
• Efficiency Limiting Factors
• Nanotubes in Solar Cell
• Conclusion

4. Introduction
• Carbon nanotubes (CNTs) are allotropes of carbon with a
cylindrical nanostructure.
• Their name is derived from their long, hollow structure with
the walls formed by one-atom-thick sheets of carbon, called
graphene.
• These sheets are rolled at specific and discrete angles.

5. Carbon Nanotubes
• S. Iijima - MWNT (1990), SWNT (1993)
• Rolled graphene sheet with end caps
• Large aspect ratios
• Unique properties

6. How CNT are made.

7. Synthesis Methods
1. Arc Discharge Method.
2. Laser Ablation Method.
3. Chemical Vapour Deposition Method.

8. 1.Arc Discharge Method
• CNT can be found in the carbon soot of
graphite electrodes during an arc
discharge involving high current.
• SWNT Diameter=1.1 to 1.4 nm.
• Inner Diameter of the MWNTs
varies in the range 1 to 3 nm.
• Outer Diameter MWNT varies
in the range of 2 to 25 nm.

9. Properties for CNTs
1. Electrical Properties.
2. Transport Properties.
3. Mechanical Properties.

10. • If the nanotube structure is
armchair then the electrical
properties are metallic.
• If the nanotube structure is chiral
then the electrical properties can
be either semiconducting with a
very small band gap, otherwise the
nanotube is a moderate
semiconductor.
Electrical Properties
A CNT is characterized by
its Chiral Vector:
Ch = n â1 + m â2,   Chiral
Angle

11. a) Armchair (n=m) f.e. (5,5)
 = 30
b) Zig Zag (n=0,m≠0) f.e (9,0)
 = 0
c) Chiral (n≠0,m≠0) f.e (10,5)
0 < < 30
(a)
(b) (c)

12. One-Dimensional Transport
• Due to their nano scale in CNT will take place
though quantum effects and will only propagate along
the axis of the tube, because of this special transport
property, CNT are frequently referred to as one
dimensional.

13. Mechanical Properties
• Very high strength,
• Modulus, and resiliency.
• Good properties on both compression and extension.

14. Three generations of solar cells

15. First Generation
• First generation cells consist of large-area, high
quality and single junction devices.
• First Generation technologies involve high energy
and labour inputs which prevent any significant
progress in reducing production costs.

16. PROBLEMS :
• Single crystalline silicon efficiency of ~ 15-16%.
• The module life is about 25 years.
• Polycrystalline silicon solar cells efficiency ~12-14% .
Cont.

17. Second Generation
• Second generation materials have been
developed to address energy requirements and
production costs of solar cells.
• Alternative manufacturing techniques such as
vapour deposition and electroplating are
advantageous as they reduce high temperature
processing significantly

18. • Thin film silicon (amorphous silicon)
• CdTe (Cadmium Telluride)
• CuInSe2 (Copper Indium Diselenide)
Cont.
PROBLEMS :
• Thin Film deposition throughput limited to 2-3 microns /
min which is not cost effective Higher throughput with
good quality opto-electronic properties required Photon
trapping structures , Passivation and Cheap Substrate
required for lowering the cost .
• Module Efficiency : ~ 10%

19. • Dye-sensitized solar cell
• Metal based dye-sensitized solar cell
• CNT based dye-sensitized solar cell

20. • Dye sensitized solar cells (DSSCs) are a relatively
new class of thin film solar cells with promising high
conversion efficiency at a low cost.
• These solar cells utilize two main components a
photo anode consisting of light absorbing dye
molecules adsorbed on a semiconductor material, and
an electrically conductive counter electrode.
• In a typical thin film solar cell, the electrodes are
made of conductive metals and Indium tin oxide.
Materials like indium are scarce and becoming more
expensive as the demand of solar cell increases.

21. • Carbon based transparent electrodes as the
replacement of conventional FTO/ITO have been
widely used in several solid-state opto- electronic
devices such as organic thin film transistors, organic
light emitting diodes.
• Because of the low cost, high durability, excellent
catalytic activity, and electrical conductivity, carbon-
based materials have been utilized as effective
alternative counter electrode for many years.
• It came to our attention that the dramatically reduced
cost and high stability of DSSCs could be achieved if
FTO/ITO and Pt in DSSCs are replaced with carbon
based materials at both working and counter
electrode.

22. • The transferred N-CNTs
and the DSSC unit cell
with N-CNT counter
electrodes are shown in
Fig.
• The DSSC fabricated with
an N-CNT counter
electrode had a slightly
higher fill factor of 0.67
and a Jsc of 14 mA cm-2 .
• A Voc of 0.767V, and a
conversion efficiency of
7.04%.

23. Cyclic voltammograms of the N-CNTs on the ITO
substrate and the Pt on the FTO substrate.

24. • N-CNT counter electrode exhibited nearly the
same peak positions as the Pt counter
electrode. The cathodic and anodic peak
current densities of the N-CNT counter
electrode were much higher than those of the
Pt electrode.
• The N-CNT counter electrode exhibits higher
electrochemical activity, which indicates that
there is a much faster reaction rate on the N-
CNTs and electron transfer rate from the
substrate to the N-CNTs.

25. • The transferred N-CNT film was tested for use as
a counter electrode for DSSCs, resulting in a
power conversion efficiency of 7.04%, while that
of a reference DSSC with a conventional Pt/TCO
counter electrode was 7.34%.
• We also demonstrated that our method is useful
for constructing flexible DSSCs. Overall, our
approach involving N-CNTs offers a promising
route to low-cost and substrate-independent Pt-
free counter electrodes for DSSCs.

26. References:
1. Wang, S. M. Zakeeruddin, P. Comte, I. Exnar and M. Gra¨
tzel, J. Am. Chem. Soc., 2003, 125, 1166; B. O’Regan and
M. Gratzel, Nature, 1991, 353, 737.
2. S. Lee, H. K. Lee, D. H. Wang, N. G. Park, J. Y. Lee, O. O.
Park and J. H. Park, Chem. Commun., 2010, 46, 4505.
3. Imoto, K. Takahashi, T. Yamaguchi, T. Komura, J.
Nakamura and K. Murata, Sol. Energy Mater. Sol. Cells,
2003, 79, 459.
4. Suzuki, M. Yamaguchi, M. Kumagai and S. Yanagida,
Chem. Lett., 2003, 32, 28.
5. Papageorgiou, P. Liska, A. Kay and M. Gratzel, J.
Electrochem. Soc., 1999, 146, 898; N. Papageorgiou, W. F.
Moser and M. Gratzel, J. Electrochem. Soc., 1997, 144, 876;

27. Thank you