Annealing of Semiconductor Blend Poly(3-hexylthiophene): Phenyl-C61-butyric acid methyl ester and Fabrication of Photovoltaic DevicesSANJANA PAPPU

Project OverviewWhat modifications affect the efficiency of a PVC device?• Temperature

• Solvents

• Duration of annealing

Properties of P3HT Poly (3-hexylthiophene)

• Excellent electron donor (functions as a p-type semiconductor)

• Regioregular structure makes it a good semiconductor

- Ordered structure helps the parallel packing of the polymer’s backbone

- Aids in facilitating the charge transport

SS

SS

S n

Regioregular

Properties of PCBM Phenyl-C61-butyric acid methyl ester• Fullerene – pure carbon molecule with a hollow inner structure• Spherical cage-like structure• Electron acceptor (functions as a n-type semiconductor)• Chemically modified to improve solubility in organic solvents

Generating a Photocurrent 1. Excitons generated in

P3HT: PCBM layer2. Excitons are spread

across the p and n-type interface

3. Dissociates into electrons and holes

4. Electrons transfer to the aluminum cathode/ holes transfer to the ITO anode

Device EfficiencyCurve represents the data of the device under illumination

Using the short-circuit current density value instead of the current eliminates the dependence of the area of the solar cell device

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8-0.008

-0.006

-0.004

-0.002

0.000

0.002

0.004

0.006

0.008

J (m

A/cm

2 )

V (V)

J SC

J max

Vmax

VOC

light

Dark

Pmax

Drop Casted P3HT

300 400 500 600 700 800 9000.0

0.2

0.4

0.6

0.8

1.0

Abso

rbanc

e (AU

)

Wavelength (nm)

Annealed at 25oC Annealed at 100oC Annealed at 150oC

Spin Coated P3HT

300 400 500 600 700 8000.0

0.2

0.4

0.6

0.8

1.0

Abso

rbanc

e (AU

)

Wavelength (nm)

Annealed at 25 oC Annealed at 90 oC

Annealed at 120 oC

Annealed at 150 oC

Spin Coated P3HT: PCBM Blend

300 400 500 600 700 8000.0

0.2

0.4

0.6

0.8

1.0

Abso

rbanc

e (AU

)

Wavelength (nm)

Annealed at 25 oC Annealed at 90 oC Annealed at 120 oC Annealed at 150 oC

P3HT and PCBM in 1 to 1 ratioin chlorobenzene (40 mg/mL)

Solvent Annealing

300 400 500 600 700 8000.0

0.2

0.4

0.6

0.8

1.0

Abso

rbanc

e (AU

)

Wavelength (nm)

Absorbance after 30 sec Absorbance after 60 sec Absorbance after 90 sec Absorbance after 120 sec

300 400 500 600 700 8000.0

0.2

0.4

0.6

0.8

1.0

Abso

rbanc

e (AU

)

Wavelength (nm)

Absorbance after 30 sec Absorbance after 60 sec Absorbance after 90 sec Absorbance after 120 sec

300 400 500 600 700 8000.0

0.2

0.4

0.6

0.8

1.0

Abso

rbanc

e (AU

)

Wavelength (nm)

Absorbance after 30 sec Absorbance after 60 sec Absorbance after 90 sec Absorbance after 120 sec

Annealed in CHCl3 Annealed in Tetrahydrofuran (THF)Annealed in CH2Cl2

Peak Comparison

300 400 500 600 700 8000.0

0.2

0.4

0.6

0.8

1.0

Abso

rbanc

e (AU

)

Wavelength (nm)

Absorbance in CHCl3 Absorbance in CH2Cl2 Absorbance in THF

Solar Cell Fabrication

Solar Simulator program calculates the PCE

Architecture of Solar Cell Device

Stefan Lab

Power Conversion Efficiency

-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0-10-8-6-4-202468

101214

Jsc (

mA/cm

-2 )

Voc (V)

25 oC 90 oC 120 oC 150oC

Temperature Jsc (mA cm-2) Voc (V) FF PCE (%)

25 oC 2.13 0.67 0.38 0.54 (0.65)

90 oC 3.76 0.58 0.36 0.80 (0.86)

120 oC 4.88 0.57 0.38 1.07 (1.11)

150 oC 6.67 0.57 0.42 1.60 (1.66)*Data in parenthesis represents the highest value

Power Conversion Efficiency

-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0-10-8-6-4-202468

101214

Jsc (

mA/cm

2 )

Voc (V)

THF CH2Cl2 CHCl3

Solvent Jsc (mA cm-2) Voc (V) FF PCE (%)

THF 4.34 0.56 0.38 0.92 (1.12)

CH2Cl2 5.51 0.53 0.35 1.03 (1.07)

CHCl3 4.34 0.55 0.37 0.91 (1.05)

*Data in parenthesis represents the highest value

ConclusionsSamples that were thermally annealed at higher temperatures displayed better current densities and efficiencies.

Samples that were solvent vapor annealed for 120 seconds absorbed more photons because the peak was at a greater wavelength. The device that was vapor annealed in methylene chloride had, on average, the best efficiency.

Annealing the samples is crucial in developing a cost-efficient solar cell.

Acknowledgements Dr. Mihaela Stefan

Jia Du Dr. Paul Pantano

Welch Foundation (AT 1740) Joon-Yong Moon

Crystal Niermann Welch Scholars Stefan Group

The University of Texas at Dallas