How to Spin Coat PEDOT:PSS

Surface Preparation

To ensure a uniform coating, it is important that the surface of your substrate is as clean as possible before you begin the deposition process. To prepare a substrate for PEDOT:PSS deposition:

Choose a substrate (FTO glass, ITO glass, or silicon) and place it in a substrate rack.
Sonicate your substrate for 5 minutes in hot (70°C) DI water with 1% Hellmanex III.
Dump-rinse twice in boiling DI water.
Sonicate your substrate for 5 minutes in isopropyl alcohol.
Dump-rinse twice in boiling DI water.
Dry your substrate using filtered compressed gas.
Place the substrate into a UV ozone cleaner and leave for 10 minutes.

How to spin coat PEDOT:PSS

For the deposition of thin films of PEDOT:PSS on a freshly prepared surface, we recommend using a vacuum-free spin coater and following this five-step process:

Filter your PEDOT:PSS solution through a 0.45 µm PES filter (or hydrophobic PTFE filter for HTL Solar 3) into an amber vial.
Preheat a hot plate to 120 °C.
Place your freshly prepared substrate into an Ossila Spin Coater and set to the desired spin speed (check spin speed/ film thickness data).
Using a micropipette, drop 100 uL of PEDOT:PSS solution onto the substrate.
The substrates should be spun until the films are dry; for PEDOT:PSS films this is typically >30 seconds.
Once the spin coating has finished, place the samples on a hotplate for 15 minutes to fully dry.

For speeds below 1000 rpm we recommend static spin coating. For higher speeds, dynamic spin coating can be used.

Obtaining a Uniform Coating

The coating quality of the PEDOT:PSS is dependent on several factors. These include the PEDOT formulation you are using, the deposition technique, the surface you are depositing onto, and the cleanliness of the surface. Ideally, the film should be highly uniform across the entire surface although variations at the ends of your sample can occur due to edge effects.

Due to the wetting conditions of the PEDOT formulation on the surface, the coating may not always be uniform. If this occurs there are several things that can be done. The first is to ensure that the surface of your sample is clean, if possible use a combination of solvent cleaning steps and UV ozone or oxygen plasma treatments to ensure a completely clean surface. If this does not improve the quality of the surface, secondary solvents can be added. For AI 4083 and PH 1000, the addition of approximately 10% isopropanol can improve the wetting on surfaces.

Learn More

Spin Coating: Complete Guide to Theory and Techniques

Spin coating is a common technique for applying thin films to substrates. When a solution of a material and a solvent is spun at high speeds, the centripetal force and the surface tension of the liquid together create an even covering.