Enhancing the Electrical Conductivity and Long‐Term Stability of PEDOT:PSS Electrodes through Sequential Treatment with Nitric Acid and Cesium Chloride

• Published in: Advanced materials (Weinheim) Vol. 36; no. 41; pp. e2405094 - n/a
• Main Authors: Adilbekova, Begimai, Scaccabarozzi, Alberto D., Faber, Hendrik, Nugraha, Mohamad Insan, Bruevich, Vladimir, Kaltsas, Dimitris, Naphade, Dipti R., Wehbe, Nimer, Emwas, Abdul‐Hamid, Alshareef, Husam N., Podzorov, Vitaly, Martín, Jaime, Tsetseris, Leonidas, Anthopoulos, Thomas D.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.10.2024
• Subjects: Carrier mobility; Cesium; CsCl; Density functional theory; Electrical properties; Electrical resistivity; Electrodes; Hall effect; HNO3; Light emitting diodes; Mechanical properties; Nitric acid; Optoelectronics; PEDOT:PSS; Photoelectrons; Polystyrene resins; post‐treatment; printed electronics; Raman spectroscopy; Spectrum analysis; Stability; Thin films; transparent electrodes; CsCl; post‐treatment; printed electronics; HNO3; transparent electrodes; PEDOT:PSS
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202405094

Solution‐processable poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is an important polymeric conductor used extensively in organic flexible, wearable, and stretchable optoelectronics. However, further enhancing its conductivity and long‐term stability while maintaining its superb mechanical properties remains challenging. Here, a novel post‐treatment approach to enhance the electrical properties and stability of sub‐20‐nm‐thin PEDOT:PSS films processed from solution is introduced. The approach involves a sequential post‐treatment with HNO3 and CsCl, resulting in a remarkable enhancement of the electrical conductivity of PEDOT:PSS films to over 5500 S cm−1, along with improved carrier mobility. The post‐treated films exhibit remarkable air stability, retaining over 85% of their initial conductivity even after 270 days of storage. Various characterization techniques, including X‐ray photoelectron spectroscopy, atomic force microscopy, Raman spectroscopy, Hall effect measurements, and grazing incidence wide angle X‐ray scattering, coupled with density functional theory calculations, provide insights into the structural changes and interactions responsible for these improvements. To demonstrate the potential for practical applications, the ultrathin PEDOT:PSS films are connected to an inorganic light‐emitting diode with a battery, showcasing their suitability as transparent electrodes. This work presents a promising approach for enhancing the electrical conductivity of PEDOT:PSS while offering a comprehensive understanding of the underlying mechanisms that can guide further advances. The conductivity of sub‐20‐nm thin poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films is improved by treating them sequentially with HNO3 and CsCl. The resulting layers show enhanced crystallinity with electrical conductivity of up to 5500 S cm−1, with 85% of this value being retained after 270 d of storage in ambient air at room temperature without being encapsulated.