Ossila provides a range of Regioregular poly(3-hexylthiophene-2,5-diyl), commonly known as P3HT, with different molecular weights and regioregularities for a variety of research purposes. Produced by Merck KGaA under the Lisicon^® brand this high quality P3HT collection allows a wider range of science and engineering to be undertaken than by using a single P3HT.

The highest regioregularity P3HT (M104, RR = 96.3%) produces highly crystalline films and is recommended for OFETs, nanofibril formation and fast drying OPVs at the thin interference peak (90 nm). However, the exceptionally high regioregularity of this P3HT means that gelling and surface roughness can be an issue for slow-drying thick-film OPVs (>200 nm). Lower molecular weight and regioregularity P3HT is recommended for inkjet and other large area or slow drying deposition techniques where gelling/aggregation and surface roughness need to be avoided.

A fabrication report with mobility measurements of 0.12 cm²/Vs for M104 can be found below.

All the P3HT below is highly soluble (50 mg/ml) in chlorinated solvents such as chloroform, chlorobenzene, dichlorobenzene and trichlorobenzene. The intermediate and lower molecular weight P3HT materials are recommended for use with non-chlorinated solvents such as xylene, toluene and THF due to their increased solubility.

General Information

OFET Fabrication Routine

Field effect mobilities in excess of 0.12 cm²/Vs are recorded using M104 when the active layer is dispensed on OTS-treated silicon oxide dielectric by static spin coating from an optimized high/low boiling point solvent mix.

High hole mobility in conjunction with good solubility and partial air stability make regioregular P3HT a reference material of choice for both fundamental and applied research in organic electronic, physics and chemistry. As one of the most well-studied organic semiconductor, P3HT is often acknowledge to be one of the benchmark against which any new p-type or donor conjugate molecule should be compared and evaluated.

Mobility has previously been found to be positively correlated with increasing region-regularity, slow drying time (achieved using high boiling point solvent), lowering of the surface energy, and molecular weight in excess of 50 kD. These conditions favour p-p stacking parallels to the OFET substrate, which in turn results in improved charge transport across the transistor channel [1-13].

The active layer solution preparation, spin coating, substrate annealing and measurements are performed in a glove box under a nitrogen atmosphere (H₂O <0.1 PPM; O₂ < 5/8 PPM).

For generic details on the fabrication of OPV devices, please see our written guide and video demonstration.

Active Layer Preparation

High-Regioregular and high molecular weight RR-P3HT (M104) (RR = 96.3%, Mw = 77,500, Mn = 38,700) is dissolved in a mix of high and low boiling point solvent in order to exploit the beneficial effect of long drying time and increase the wettability of low energy surface, respectively.

• 5 mg/ml of M104 dissolved in anhydrous Chloroform:Trichlorobenzene (99:1) mix;
• Vial is placed on hot plate (70°C) with a stirrer bar for 30 minutes;
• Solution cooled down at room temperature and then filtered with a 0.45 µm PTFE (hydrophobic) filter;
• Solution stored overnight on a hot plate at 30°C to prevent excessive aggregation of the P3HT molecules.

Substrate Cleaning

• Substrates loaded on to substrate rack (to keep them in upright position);
• Sonicated in hot Hellmanex III solution (1%) for five minutes;
• Rinsed twice in hot water;
• Sonicated in warm Isopropyl alcohol (70°C) for five minutes;
• Rinsed twice in cold DI water;
• Substrates stored in DI water.

Thermal Deposition of Electrodes and Contact Pads

• Done on Edwards 306 Thermal coater in clean room condition;
• Substrates are blown dry and loaded in a low density evaporation stack with a low density shadow mask to pattern the desired features;
• Secondary mask is added to selectively evaporate the gate and drain/source pads;
• Vacuum chamber pumped down to a vacuum pressure of 5 x 10^-6 mbar;
• Chromium adhesion layer: 5 nm, rate 0.05 nm/s;
• Aluminium: 80 nm, rate: 0.4 nm/s;
• Changed secondary mask to deposit electrodes (FET channels);
• Vacuum: 2-3 x 10^-6 mbar;
• Chromium adhesion layer: 1 nm, rate 0.05 nm/s;
• Gold: 40 nm; rate 0.05 nm/s.

PFBT Treatment for Au Electrodes (Laminar flow)

• Oxygen plasma treatment, 30 seconds at 100 W;
• Substrates immersed in 2.5 mMol/l solution of PFBT in isopropyl alcohol at room temperature;
• Substrates rinsed twice in pure isopropyl alcohol;
• Substrates are blown with nitrogen gun.

OTS Treatment for SiO₂ Dielectric (Laminar flow)

• A solution of OTS (25 microlitres) in cyclohexane (anhydrous grade, 1 ml) prepared in glove box;
• Substrates (pre-loaded on a substrate rack) loaded into the annealing beaker, which is filled with approx. 50 ml of cyclohexane in a fume hood;
• Previously prepared OTS solution quickly added to the cyclohexane and mixed with a pipette tip;
• The glass lid is placed halfway onto the beaker, which is carefully filled with more cyclohexane until it is full and the lid is fully closed;
• The final solution (60 ml) contains OTS at a concentration of 1 mMol/l;
• Substrates kept for 20 minutes in the OTS solution;
• Substrates removed from the OTS solution, quickly rinsed twice in clean cyclohexane, and then are blown dry with nitrogen gun.

Contact Angle Assessment

The water-drop test on the treated silicon is a quick test to qualitatively assess the effect of the OTS on the silicon substrates to ensure that the fabrication has functioned correctly. You can get a good approximation of the contact angle using your eye or a simple digital photo.

Previous quantitative assessments have shown that this routine will produce contact angles between 90 and 110°C (depending on the lab temperature, humidity and other factors). You can quantify that contact angle easily and accurately using the Ossila Contact Angle Goniometer.

P3HT (M104) spin coating (glove box)

• 30 µl of Organic Semi-Conductor (OSC) solution delivered on the middle of the substrate and then spin coated at 1000 rpm for 10 s followed by 60 s at 2000 rpm;
• Cotton swab soaked in chlorobenzene to thoroughly wipe clean the contact pads and the rest of the substrates with the exception of the area around the channel;
• High precision cotton swab to clean between devices to avoid cross-talking and reduce leakage;
• Substrates annealed at 90°C for 30 minutes;
• Cooled down for ten minutes;
• Five devices per substrate are characterised using OFET Test Board for Low-Density OFETs in a glove box;
• Second annealing at 120°C for 20 minutes, slow cooling down at room temperature and measurement;
• Annealing at 150°C for 20 minutes, slow cooling down at room temperature and measurement.

MSDS Documentation

P3HT MSDS sheet

Batch Details

The below P3HT is in stock for immediate dispatch.

To the best of our knowledge the technical information provided here is accurate. However, Ossila assume no liability for the accuracy of this information. The values provided here are typical at the time of manufacture and may vary over time and from batch to batch.