Fully transparent and superhydrophobic electrodes enabled by soft interfaces

The simultaneous achievement of transparency, electrical conductivity and superhydrophobicity is a highly challenging and rewarding task for a range of technological applications. This manuscript reports a practical and fluorine-free approach for fully transparent and superhydrophobic coatings on a transparent electrode. The first step consists of the formation of a grafted film of poly(ethylene glycol) on an indium oxide coated glass substrate. The superhydrophobicity is then achieved by spray-coating a film of alkylsilane functionalized nanoparticles. The self-assembly of the hydrophobic nanoparticles on end-grafted poly(ethylene glycol) allows for controlled formation of roughness without sacrificing the transparency and electrical conductivity. The result is a multi-functional substrate with a static contact angle of 172°, sliding angle of 1°, 90.4% transparency at a wavelength of 550 nm, and a sheet resistance of 13.05 Ω/sq. The surface has high water impact-resistance and thermal stability provided by the soft-interface composed of end-grafted poly(ethylene glycol). The reported substrate exhibits outstanding figures of merit in terms of the water repellency, optoelectronic performance, and stability. Application in transparent heaters demonstrates the promise of the presented multi-functional coatings.