![Motivation from Solar Cell Diode Model
2
Bilayer organic diodes Power law found from fit to IV curves
3(x/0.68)
12
)
-1
+ (70(x/0.68)
5.2
)
-1
)
-1
)
-1
+ (100(x/0.68)
2
)
-1
)
-1
(x/1.2)
21
)
-1
+ (53(x/1.2)
6.7
)
-1
)
-1
)
-1
+ (237(x/1.2)
2
)
-1
)
-1
23(x/1.5)
25
)
-1
+ (24(x/1.5)
6.9
)
-1
)
-1
)
-1
+ (165(x/1.5)
2
)
-1
)
-1
V11.9
V
21.1
V24.9
Current[mA/cm
2
]
10−3
10−2
10
−1
1
10
1
10
2
10
3
Voltage [V]
0.1 1
F16CuPc
C60
hNDI
Dark Currents](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
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2020 APS March Meeting: Evidence for an accumulation layer at the donor-acceptor interface in organic solar cells
- 1. Evidence for an Accumulation Layer at the Donor-acceptor Interface in Organic Solar Cells Xinrui Zhu*, Christina McGahan*, Dhandapani Venkataraman#, Alexi Arango*, Katherine Aidala* 1 * Mount Holyoke College, # University of Massachusetts Amherst
- 2. Motivation from Solar Cell Diode Model 2 Bilayer organic diodes Power law found from fit to IV curves 3(x/0.68) 12 ) -1 + (70(x/0.68) 5.2 ) -1 ) -1 ) -1 + (100(x/0.68) 2 ) -1 ) -1 (x/1.2) 21 ) -1 + (53(x/1.2) 6.7 ) -1 ) -1 ) -1 + (237(x/1.2) 2 ) -1 ) -1 23(x/1.5) 25 ) -1 + (24(x/1.5) 6.9 ) -1 ) -1 ) -1 + (165(x/1.5) 2 ) -1 ) -1 V11.9 V 21.1 V24.9 Current[mA/cm 2 ] 10−3 10−2 10 −1 1 10 1 10 2 10 3 Voltage [V] 0.1 1 F16CuPc C60 hNDI Dark Currents
- 3. Power m and Accumulation Layer 3 Accumulation of charge depends on Δ𝐸Plot power m versus Δ𝐸 m =ΔE /2.5kT +1Full model fits PowerLawExponent(m) 0 5 10 15 20 25 ΔE [eV] 0 0.5 1.0 1.5
- 4. Bilayer Field Effect Transistors 4 D Copper(II) phthalocyanine 1,4,5,8- Naphthalenet- etracarboxylic dianhydride CuPC NTCDA -3.4 eV -5.0 eV -4.5 eV -7.4 eV
- 5. Bilayer Field Effect Transistors 5 Oxide Gate CuPC Oxide Gate CuPC NTCDA 50 nm CuPC 30 nm NTCDA on 50 nm CuPC Bphen Bphen7 nm Bphen S DS D CuPC NTCDA -3.4 eV -5.0 eV -4.5 eV -7.4 eV
- 6. Drain Sweeps CuPC Drain Sweep NTCDA on CuPC Drain Sweep 6 Oxide Gate CuPC Oxide Gate CuPC NTCDA CuPC NTCDA -3.4 eV -5.0 eV -4.5 eV -7.4 eV
- 7. Gate Sweeps and Mobility CuPC Gate Sweep NTCDA on CuPC Gate Sweep 7 𝜇 = 1.77× 10−3 𝑐𝑚2 𝑉−1 𝑠−1 𝜇 = 3.97× 10−3 𝑐𝑚2 𝑉−1 𝑠−1
- 8. Physics 1: Transporting Channels 8 Oxide Gate CuPC NTCDA Oxide Gate CuPC + + + + + + + + + + - - - - - ----- + ++++++ - - -----
- 9. Physics 2: Band Bending 9 CuPC OxideGate + ElectronEnergy CuPC NTCDA -3.4 eV -5.0 eV -4.5 eV -7.4 eV CuPC NTCDA
- 10. Physics 2: Band Bending 10 CuPC NTCDA OxideGate CuPC OxideGate - + + + ElectronEnergy
- 11. Summary 11 Depositing NTCDA on top of CuPC results in: 1. Increase in Mobility (factor of 2-3) 2. Positive shift in threshold voltage (60V)
- 12. Future Plans 12 1. Additional electrical measurements including band bending 2. Different combinations of materials 3. Direct comparison with solar cell performance
- 13. Acknowledgements • The Aidala lab • The Arango lab • This work is made possible by: – Research in Undergraduate Institutions grant NSF- DMR 1708970 – STC Center for Integrated Quantum Materials grant NSF-DMR 1231319 13
- 14. Thank You! Any Questions or Comments: zhu32x@mtholyoke.edu 14
Editor's Notes
- Schematic of solar cell Energy Level New model Power law relationship hNDI—hexyNDI F16CuPC
- Linear trend Space charge model accumulation layer depend on Δ𝐸
- P type (donor) n type (acceptor) FET Thermal evaporator insulating capping layer
- P type (donor) n type (acceptor) FET Thermal evaporator insulating capping layer
- Drain Sweep intro Currents in only negative gate voltage more currents positive gate voltage
- Gate Sweep intro Consistent Increase in mobility Threshold voltage
- Negative gate voltage attracts holes A parallel transporting channel We can understand it better through band bending—next slide
- Bend due to electric field energy difference :bend toward each other bend on two sides
- Bend due to electric field energy difference :bend toward each other bend on two sides
- Consistent with our model. Do more work to eliminate doping as an explanation. (acknowledge it!)
- we clearly need to do a lot more work. directly measure band bending with KPFM. we want to compare with… Our new power law model and theory that the accumulation layer depends on energy difference