Magnetic Field Modulated Photovoltage Ned Booker Cavendish Laboratory 1.
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Transcript of Magnetic Field Modulated Photovoltage Ned Booker Cavendish Laboratory 1.
1
Magnetic Field Modulated Photovoltage
Ned Booker
Cavendish Laboratory
2
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 )
8
Magneto-Photovoltage
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Magneto-Photocurrent
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Recombination Model
So
S1
A. Rao, et al., Nature 500, 435 (2013)
11
Recombination Model
So
S1
ISC
kdis,sing
CTT CTS
A. Rao, et al., Nature 500, 435 (2013)
12
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)
14
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