Multi-mode humidity sensing with water-soluble copper phthalocyanine for increased sensitivity and dynamic range

Area of Science:

• Materials Science
• Physical Chemistry
• Electronics Engineering

Background:

• Aqueous solubility of copper phthalocyanine-3,4',4″,4″'-tetrasulfonic acid tetrasodium salt (CuPcTs) facilitates low-cost inkjet printing for flexible electronics.
• Understanding water adsorption on CuPcTs is crucial for optimizing its performance in varying humidity conditions.

Purpose of the Study:

• To investigate the water adsorption kinetics on CuPcTs.
• To evaluate CuPcTs as a potential humidity-sensing material.

Main Methods:

• Investigated water adsorption using reaction models and gravimetric measurements.
• Employed high and low frequency dielectric spectroscopy.
• Utilized principal component analysis for data interpretation.

Main Results:

• Identified a two-site sequential pseudo-first order reaction model for water adsorption.
• Observed significant opto-electrical changes in CuPcTs at approximately 60% relative humidity (RH).
• Demonstrated that CuPcTs can accurately sense humidity across a wide range (0-95% RH) with a low detection limit (<0.1% RH).

Conclusions:

• CuPcTs exhibits distinct water adsorption behaviors at low and high RH, influencing its dielectric properties.
• The material shows promise as a sensitive and accurate humidity sensor for electronic applications.