Electro-Responsivity in Electrolyte-Free and Solution Processed Bragg Stacks

Achieving an active manipulation of colours has huge implications in optoelectronics, as colour engineering can be exploited in a number of applications, ranging from display to lightning. In the last decade, the synergy of the highly pure colours of 1D photonic crystals, also known as Bragg stacks, with electro-tunable materials have been proposed as an interesting route to attain such a technologically relevant effect. However, recent works rely on the use of liquid electrolytes, which can pose issues in terms of chemical and environmental stability.<br/>Here, we report on the proof-of-concept of an electrolyte free and solution-processed electro-responsive Bragg stack.¹ We integrate an electro-responsive plasmonic metal oxide, namely indium tin oxide, in a 1D photonic crystal structure made of alternating layers of ITO and TiO₂ nanoparticles. In such a device, we observed a maximum of 23 nm blue-shift upon the application of an external bias (10 V). Our data suggest that electrochromism can be attained in all-solid state systems by combining a judicious selection of the constituent materials with device architecture optimisation.<br/><br/><i>1. Moscardi et al., J. Mater. Chem. C</i>, 2020,8, 13019-13024