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Solar Cell

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Farzaneh vll

on 8 December 2013

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Transcript of Solar Cell

2. Experimental
4. conclusion
In summary, TiO2 nanoparticles synthesized hydrothermally and used for CdS QDSSC applications. Due to higher surface area CdS QDSSC with TiO2 nanoparticles exhibit higher photocurrent and photovoltage compared to CdS QDSSC with industrial TiO2, also central composite design was employed to optimize and study the individual and interactive effect of process variable such as Cd and sulfide concentration and number of cycle on the photocurrent response of CdS quantum dot sensitized solar cells.

Preparation of TiO2 nanoparticles and CdS quantum dots and their application in dye sensitized solar cells
Farzaneh Valilou
Supervisors:Dr.R. Sabzi, Dr.M.Bahram, Dr.F. Kheiri

1. Introduction
A solar cell (also called a photovoltaic cell) is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect.

How do they work?
Solar cells development

2. Thin films
Three generation of solar cells:
1. Single-crystal silicon based photovoltaic devices
3. Nanotechnology –enhanced solar cells
Bulk Heterojunction (BHJ) photovoltaic cells or organic photovoltaic cells
Dye-sensitized Solar Cells (DSSC)
Quantum Dot Solar Cells (QDSC).
Nanotechnology –enhanced solar cells:

Quantum Dots:
Quantum dots are semiconductors that are on the nanometer scale.
Unlike ordinary bulk semiconductors, which are generally macroscopic objects, quantum dots are extremely small, on the order of a few nanometers. They are very nearly zero-dimensional
The size ,shape and number of electrons can be precisely controlled.
Exhibit energy band gap that determines required wavelength of radiation absorption and emission spectra
Requisite absorption and resultant emission wavelength dependent on dot size.
Advantages of using QDs as sensitizer in solar cells:
Higher molar extinction coefficient of QDs than Dyes
Tunable energy gaps
Multiple exciton generation

Basic QDSC Layers:

The proper assembly and ordering of semiconductor QDs in a mesoscopic oxide film is an essential criterion for designing QDSC.
Sensitization of a wide gap nanostructured semiconductor electrode with QDs is done by:

Long term stability is an important criterion. It affects the fill factor and hence efficiency of the cell.
Synthesis of TiO2 nanoparticles:
The industrial TiO2 powders were mixed with 10 M NaOH, and mixture was stirred for 30 min. Afterwards, it was heated at 135 ˚C for 24 h.
TiO2 Layer
Sensitization of TiO2 layer
Doctor Blade method
Using SILAR method by dipping TiO2 film into a 0.1 M Cd(NO3)2 ethanol/water solution for 1 min, rinsed with ethanol and then dipping into the Na2S methanol/water solution for 1 min and rinsed with methanol, this two-step procedure was repeated for 15 times.
The polysulfide electrolyte was composed of 2 M S, 0.5 M Na2S, and 0.2 M KCl in the solvent with the methanol/water ratio of 7/3 (by volume)
The graphite on the FTO conductive glass and bare FTO glass was used as the photocathode.
Solar Cell Assembly
Comparison of I-V curves for two preparation methods of photoanode:
Central composite design and surface response methods was used to determine the optimal conditions and study the effect of three variables on response.
Electrochemical behavior of TiO2 layer in the presence and in the absence of light:
Influence of temperature on the electrochemical behavior of polysulfide electrolyte:
Uncoded values of the independent variables and observed responses.
Studied models:
Surfaces were constructed to predict the relationship between the independent variables and responses.
Surface response method:
Optimum values:
The principle of operation of QDSC is based on the semiconductor−liquid junction photoelectrochemistry:

Comporison of solar cell made with TiO2 nanoparticles and industrial TiO2:
I-V curves to compare the performance of different photocathode:
Experimental Design:
Some features of the model:
3. Result and Discussion
Thank you!
For the operation of a DSSC or QDSSC, a good electrolyte with a redox mediator is required. The redox mediator regenerates the oxidized sensitizer by donating an electron.
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