PFN, PFN-DOF

CAS Number 673474-74-3

Cathode Interlayer Materials (CIMs), Interface Polymers, Materials, Organic Conductors, Perovskite Interface Materials, Perovskite Materials, Semiconducting Polymers

MSDS

High Quality Semiconducting Polymer

Improved extraction efficiencies in OPV devices

Product Information | MSDS | Pricing | Literature and Reviews

PFN (CAS number: 673474-74-3) is a conjugated polyelectrolyte used as an electron-interface in OPV devices to improve extraction efficiencies. Currently producing power conversion efficiencies of up to 7.1% at Ossila, with further increases expected from additional optimization and up to 9.2% reported in the literature [1-3].

Good Solubility

In polar solvents with small amount of acetic acid

Cathode Interlayer Molecule

For high efficiency OPVs

Improve Extraction Efficiency

Conjugated polyelectrolyte

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PFN from Ossila was used in the high-impact paper (IF 30.85), All-Organic and Fully-Printed Semitransparent Photodetectors Based on Narrow Bandgap Conjugated Molecules, G. Pace et al., Adv. Mater., 26, 6773-6777 (2014); DOI: 10.1002/adma.201402918.

Product Information

Full Name	Poly [(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9–dioctylfluorene)]
Synonyms	PFN, PFN-DOF
Chemical Formula	(C₅₂H₇₀N₂)_n
CAS Number	673474-74-3

Chemical Structure

Batch Information

Batch	M_w	M_n	PDI	Stock info
M222	N/A	N/A	N/A	Low stock
M0221A1	85,000	44,973	1.89	In stock

Usage details

Inverted OPV devices were made using the architecture shown below with PFN as an electron-interface and PTB7:PC₇₀BM in a 1:1.5 blend ratio. Ossila's pixelated cathode substrate pack (S213) provided the device components.

Glass / ITO (100 nm) / PFN (5.5 to 10 nm) / PTB7:PC₇₀BM (90 nm) / MoO_x (15 nm) / Al (100 nm)

The substrate cleaning and PFN spin-coating were performed under ambient conditions with all other steps performed in an N₂ glove box until encapsulation had been completed (measurement performed under ambient conditions).

The active layer thickness, MoO_x thickness, cathode metal (Ag or Al), PFN solution concentration, PFN drying/baking have not been fully optimized. As such, we expect further gains to be made with additional engineering work. However, for the devices made in this fabrication, a peak efficiency of 7.1% was achieved.

Efficiency for different PTB7 spin speeds - Standard architecture — PCE, Jsc, Voc and FF for different spin speeds. Data shown is averaged with max and min overlaid with filled circles.

Jsc for different PTB7 spin speeds - Standard architecture — PCE, Jsc, Voc and FF for different spin speeds. Data shown is averaged with max and min overlaid with filled circles.

PTB7 JV Curve for inverted architecture — The JV curve for the best performing device.

Note that some burn-in was observed (i.e. a small improvement in device performance after a few seconds under the solar simulator) and the variability of the devices is currently slightly higher than for other interlayers (average PCE of 6.7%). We expect the uniformity to improve with further improvements in PFN processing, in particular the optimization of drying conditions to ensure that the acetic acid is fully removed prior to active layer deposition.

Fabrication Routine

The below fabrication routine was used to fabricate inverted solar cells with peak efficiency of 7.1%. Further gains are expected with further optimization.

Cleaning Substrates

Pixelated Cathode substrates (S213)
5 mins sonication in hot Hellmanex III (1 ml in beaker)
2x boiling water dump rinses
5 mins sonication in warm IPA
2x dump rinses
5 mins sonication in hot NaOH
Dump rinse in boiling water
Dump rinse in water
Stored in DI water overnight and until use

PFN solution

Stock solution of acetic acid dissolved 1:9 in methanol to enable low concentration solutions to be made more easily.
Acetic acid solution further dissolved to produce 2 μl/ml solution.
PFN dissolved at 2 mg/ml in methanol with 2 μl/ml of acetic acid with stir bar at ambient temperature for 10 minutes
Filtered through 0.45 µm PES filter

PFN Test Films

PFN Test film initially spun at 500 rpm and gave 21-22 nm
Second test film spun at 1000 rpm and gave 13-16 nm
Thicknesses extrapolated for higher spin speeds
It was noted that at low spin speeds 500 rpm to 2400 rpm there were significant crystallites present in the films - especially on the ITO. Extra filtration showed that this was not due to the solution and therefore most have been due to the drying process

Active Layer Solution

Fresh stock solution of PTB7 made on at 10 mg/ml in CB and dissolved with stir bar for 1 hour (dissolves very easily)
Mixed 1:1.5 with dry Ossila 95/5% C70 PCBM to make overall concentration of 25 mg/ml and dissolved with stir bar for 1 hour more
3% of diiodooctane (DIO) added to solution
Filtered using 0.45 μm PTFE (hydrophobic) syringe filter

Active Layer Test Films

Test film spun at 1000 rpm for 2 mins using unfiltered solution and thickness measure on Dektak. Note that films must be fully dry before performing Dektak measurements.
1000 rpm gave approximately 90 nm thickness.

Active layers

Devices spun using 30 μl dynamic dispense (20 μl gave only moderate wetting/coverage)
Spun for 2 mins
Cathode wiped with CB
Vacuum dried in glove box antechamber for 20 mins to remove residual DIO from films

Cathode Evaporation

15 nm of MoO_x evaporated at 0.2 Å/s from fresh pellets at pressure 1e-6 mbar
100 nm of Al evaporated at 1.5 Å/s at pressure 1e-6 mbar

Annealing/Encapsulation

No annealing performed
Encapsulated as standard, using Ossila encapsulation epoxy (E132) and glass coverslips (C181) (30 mins in UV light box).

Measurements

JV sweeps taken with Keithley 237 source-meter
Illumination by Newport Oriel 9225-1000 solar simulator with 100 mW/cm² AM1.5 output
NREL certified silicon reference cell used to calibrate lamp output
Lamp current: 7.9 A
Solar output at start of testing: 0.995 suns at 25°C
Solar output at end of testing: 1.00 suns at 25°C
Electrochemically etched aperture mask was optically calibrated to 0.212 cm²

MSDS Documentation

PFN MSDS sheet

Literature and References

Enhanced power-conversion efficiency in polymer solar cells using an inverted device structure, Z. He et al., Nature Photonics, 6, 591–595 (2012)
Simultaneous Enhancement of Open-Circuit Voltage, Short-Circuit Current Density, and Fill Factor in Polymer Solar Cells, Z. He et al., Advanced Materials, 23, 4636–4643 (2011)
Investigation of a Conjugated Polyelectrolyte Interlayer for Inverted Polymer:Fullerene Solar Cells, R. Xia et al., Advanced Energy Materials, (2013)

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