Tailoring Characteristics of PEDOT:PSS Coated on Glass and Plastics by Ultrasonic Substrate Vibration Post Treatment

Abstract

In this work, we excited as-spun wet films of PEDOT:PSS by ultrasonic vibration with varying frequency and power. This is a low-cost and facile technique for tailoring the structural and surface characteristics of solution-processed thin films and coatings. We deposited the coatings on both rigid and flexible substrates and performed various characterization techniques, such as atomic force microscopy (AFM), scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), transmittance, electrical conductivity, and contact angle measurements, to understand how the ultrasonic vibration affects the coating properties. We found that as a result of ultrasonic vibration, PEDOT:PSS sheet conductivity increases up to five-fold, contact angle of water on PEDOT:PSS increases up to three-fold, and PEDOT:PSS roughness on glass substrates substantially decreases. Our results affirm that ultrasonic vibration can favor phase separation of PEDOT and PSS and rearrangement of PEDOT-rich charge transferring grains. In addition to providing a systematic study on the effect of ultrasonic frequency and power on the film properties, this work also proves that the ultrasonic vibration is a novel method to manipulate and tailor a wide range of properties of solution-processed thin films, such as compactness, chain length and arrangement of polymer molecules, conductivity, and surface wettability. This ultrasonication method can serve organic, printed and flexible electronics.

Experimental study on travelling and standing pattern formation and capillary waves in a pinned liquid film: effects of multi-axis lateral (horizontal) vibrations and substrate geometry

“…Although at this high frequency the amplitude of vibration was small, i.e. ∼0.5 nm (Gholampour et al 2018), this experimental observation is in qualitative agreement with the theoretical work of Shklyaev, Alabuzhev & Khenner (2009), who suggested that film stability could be achieved for very-high-frequency ultrasonic horizontal vibrations.…”

“…However, at this frequency, we can clearly see that the intensity of the waves (even for the regions where it is the highest) is lower than the intensity of the 20 and 40 kHz cases. This gradual decrease in the wave amplitude with increasing excitation frequency and then the complete disappearance of waves at f = 170 kHz agree with the fact that the amplitude of excitation decreases with frequency (Gholampour et al 2018).…”

“…Stability of the film at 170 kHz is attributed to the very low amplitude of excitations created at this high frequency, since at a given input power to the ultrasonic transducer, the amplitude decreases with an increase in the frequency. In addition, the impedance mismatch between the ultrasonic transducer and the liquid film increases with an increase in the excitation frequency; therefore, the ultrasonic radiation cannot effectively transmit into the liquid film (Gholampour et al 2018) and a larger portion of it will be reflected.…”

“…A signal generator was used to actuate the transducer (Yuhuan Clangsonic Ultrasonic Co. Ltd, Zhejiang, China). The detailed characterization of the ultrasonic vibrators by laser beams is provided elsewhere (Gholampour, Brian & Eslamian 2018). Table 2 shows the range of input parameters used in the experiments.…”

All solution-processed ITO free flexible organic light-emitting diodes

“…The RMS roughness of the 800 DPI Ag coated substrate is measured by laser interference and is 6 AE 1 nm. It is slightly larger than that of PET/ITO found in the literature (3.32 AE 0.53 nm) 61 and similar to those of other printed Ag layers. 24 The roughness and the sheet resistance are low enough to build efficient OLEDs on top of the ink-jet printed Ag.…”