Solution-Processed Transparent Superhydrophobic Protection Layers for Enhancing the Device Reliability of Flexible Organic Optoelectronics

Organic materials and devices have attracted great attention for implementation of flexible and transparent electronics applications. However, further easy-to-manage organic devices with acceptable environmental reliability in open air are desirable. Specifically, because water-based threats and particle contamination can degrade the functions of organic optoelectronics, introducing a superhydrophobic protection layer onto organic devices, which can eliminate issues via excellent water repellency, is necessary. In this study, surface-engineered TiO₂ nanoparticles dispersed in a highly fluorinated solvent are deposited on organic devices using organo-compatible solution processing. The optimization of the TiO₂ nanoparticle layer, such as the surface roughness and thickness of the film, enables the realization of a transparent superhydrophobic layer; therefore, the film can be utilized in transparent organic optoelectronics, especially in phototransistor applications. The transparent superhydrophobic layer exhibits good water repellency without critical delamination issues even during mechanical deformation, such as bending and stretching tests. Flexible organic phototransistors with the transparent superhydrophobic layer show a self-cleaning ability against harmful contaminants on the topmost surface, achieved by dropping water droplets. This work can provide a feasible solution to maintaining transparent and flexible organic devices with improved environmental reliability.