Magnetic Field Modulated Photovoltage Ned Booker Cavendish Laboratory 1.
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1
Magnetic Field Modulated Photovoltage
Ned Booker
Cavendish Laboratory
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Origin of Photovoltage
J. Nelson, The Physics of Solar Cells (Imperial College Press, 2003)
Conduction Band
Valence band
Energy
Incident light
Ev
Ec
EFe
EFhVoc
Eg
𝑉 𝑜𝑐=𝐸𝑔+𝑘𝐵𝑇 ln( 𝑛𝑝𝑁 𝑝𝑁𝑣 )
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Magnetic Field Effects
Intersystem Crossing(modulated by B field)
Particle Pairs
Free particles
Yield depends on pair spin
M. Cox, Technische Universiteit Eindhoven (2015)
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Experimental Set-Up
Keithley 2400
sourcemeter
Magnet power supply
Device
Electromagnet Poles
White LED ring
Blue LEDLens
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Variation of Magnetic Field
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Photocurrent
A. Rao, et al., Nature 500, 435 (2013)
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Photovoltage
𝑉 𝑜𝑐=𝐸𝑔+𝑘𝐵𝑇 ln( 𝑛𝑝𝑁 𝑝𝑁𝑣 )
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Magneto-Photovoltage
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Magneto-Photocurrent
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Recombination Model
So
S1
A. Rao, et al., Nature 500, 435 (2013)
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Recombination Model
So
S1
ISC
kdis,sing
CTT CTS
A. Rao, et al., Nature 500, 435 (2013)
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Recombination Model
So
To
S1
CTT CTS
ISCFree charges
krec,trip
kdis,sing
kdis,CT
A. Rao, et al., Nature 500, 435 (2013)
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Recombination Model
So
To
S1
CTT CTS
ISCFree charges
krec,trip
kdis,sing
kdis,CT
krec,bimol
A. Rao, et al., Nature 500, 435 (2013)
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Transient Photovoltage
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Fitted decay rates
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Conclusion
• Magneto-photovoltage
• Magneto-photocurrent
• Transient Photovoltage
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Outlook and Further Work
• Polymer:Fullerene ratio• Dope heavy metals• Perovskites (why not)• Quantum dots• Develop kinetic model• Any other suggestions…?
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Thanks
• Professor Neil Greenham• Akshay Rao • Dan Credginton• Marc Etherington• Maxim Tabachnyk
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Outlook and Further Work
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Outlook and Further Work
M. Qian, et al., Advanced Materials 27, 3546 (2015).
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Photovoltage with Blend Ratio
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Different blend ratio devices
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Repeatability and Artifacts
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Reports of Magneto-Photocurrent
F.Wang, H. Bässler, Z. Valy Vardeny, Physical Review Letters 101, 236805 (2008).
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Conclusion
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Device Fabrication
PTB7-PCBM PIDTphanQ-PCBMPEDOT spin-speed (rpm) 4000 4000
Anneal Time (min), Temp (°C) 30, 150 30, 140
Polymer blend solvent DCB, DIO DCB
Active layer spin-speed (rpm) 2000 800 for 120 s, 2000 for 5 s
Anneal Time (min), Temp (°C) N/A 10, 110
Metal Contact (thickness (nm)) Ca (30), Al (100) Ca (30), Al (100)
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Transient Photovoltage