Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

Performance of Graphene as Cathode Electrode and Active

Layer Material

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

•FTO (Fluorine Tin Oxide) • One of the most employed material as cathode electrode in solar cell

• Efficiency of FTO in solar cells:

0.84 %

Graphene - Cathode Electrode

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

•ITO (Indium Tin Oxide)• Another popular material for solar cells as electrode material.

• Efficiency of ITO in solar cells:

1.17 %

Graphene - Cathode Electrode

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

What about graphene’s performance as cathode

electrode material ?

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

• Efficiency of graphene based solar cell:

0.26% to 0.29%

Graphene - Cathode Electrode

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

• Efficiency of solar cell based on graphene is lower than others

• Graphene has higher:• Electrical and • Chemical properties

• So why low efficiency?• Sheet resistance of graphene layers.

Graphene - Cathode Electrode

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

• When we cover the subtract (glass) with graphene, layers are not fixed smoothly• Can not achieve layer thickness we desire • Thus, can not achieve:

• Optimum resistance • Transmittance• Efficiency values

Graphene - Cathode Electrode

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

•How we can make graphene based solar cell more efficient?

•How we can produce thinner and less resistive graphene

layers ?

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

•CVD (Chemical Vapor Deposition)• Produces single to few graphene layers• Approximately 1-10 layers graphene sheets

• Advantages:• Inexpensive • Applicable to large areas

Graphene - Cathode Electrode

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

• CVD (Chemical Vapor Deposition)• Evaporated Ni primary subtract• Glass or Si alternative subtract

• We can use:• CVD method plating on glass with graphene

• Graphene as cathode electrode material

Graphene - Cathode Electrode

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

• Comparison of Glass and Graphene layer • 3 nm graphene layer that plated by CVD method.

• Transparency is about 90% between 400-1000 nm wavelength. • Resistance of layer is about 700 Ω/sq• Graphene with CVD method:

• Very strong candidate for cathode electrode material

Graphene - Cathode Electrode

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

Graphene as a Active Layer Material

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

• Comparison of two active layers:•Graphene-P3HT based solar cell•Pristine-P3HT based solar cell

Graphene – Active Layer Material

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

• Power conversion efficiency:• Under same illumination

Pristine P3HT based device Graphene-P3HT based device

0.5% 15%

Graphene – Active Layer Material

Graphene Wins

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

• Another important factor for efficiency:• Percentage of graphene in the content

• If we increase the amount of graphene in the content monotonically: • The efficiency increases at first and then degrades

vs.

Graphene – Active Layer Material

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

• Optimum value: 10% graphene in the content. • After this ratio, efficiency start to decrease.

Graphene – Active Layer Material

GRAPHENE CONTENT 0% 2.5% 5% 10% 15%POWER

CONVERSION EFFICIENCY

0.5% 9% 10% 15% 13%

Optimum value

Effic

ienc

y

Amount

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

• Annealing Treatment • Another important factor for efficiency• Also known as Heat Treatment• Alters the physical, and sometimes chemical, properties of a material • In our case, treatment increases efficiency

Graphene – Active Layer Material

GRAPHENE CONTENT 2.5% 5% 10% 15%

EFFICIENCY(After Annealing) 0.55% 0.69% 1.1% 0.35%

Optimum value

Ali Bilge GuvencAli Bilge Guvenc11, Huseyin Sarialtin, Huseyin Sarialtin22

Department of Electrical EngineeringDepartment of Electrical Engineering11, Department of Mechanical , Department of Mechanical EngineeringEngineering22

Graphene Solar CellsGraphene Solar Cells

Conclusion

• Graphene produced by CVD method is a very strong candidate for cathode electrode material in solar cells.

• If graphene is used as active layer material with P3HT in solar cells, especially after annealing treatment, efficiency increases significantly. Graphene can be considered as a nice active layer material in solar cells.