Photo-enhanced ionic conductivity across grain boundaries in polycrystalline ceramics

Grain boundary conductivity limitations are ubiquitous in material science. We show that illumination with above-bandgap light can decrease the grain boundary resistance in solid ionic conductors. Specifically, we demonstrate the increase of the grain boundary conductance of a 3 mol% Gd-doped ceria thin film by a factor of approximately 3.5 at 250 degrees C and the reduction of its activation energy from 1.12 to 0.68 eV under illumination, while light-induced heating and electronic conductivity could be excluded as potential sources for the observed opto-ionic effect. The presented model predicts that photo-generated electrons decrease the potential barrier heights associated with space charge zones depleted in charge carriers between adjacent grains. The discovered opto-ionic effect could pave the way for the development of new electrochemical storage and conversion technologies operating at lower temperatures and/or higher efficiencies and could be further used for fast and contactless control or diagnosis of ionic conduction in polycrystalline solids. Grain boundary conductivity limitations are ubiquitous in material science. Illumination with above-bandgap light is now shown to decrease grain boundary resistance in a model gadolinium-doped ceria solid ionic conductor.

Automated summary

The study shows that grain boundary resistance in solid ionic conductors can be decreased by illuminating with above-bandgap light. Experimental results demonstrate the increase in grain boundary conductance of a 3 mol% Gd-doped ceria thin film by approximately 3.5 times at 250 degrees C, with the reduction of activation energy from 1.12 to 0.68 eV under illumination. The discovered opto-ionic effect could potentially contribute to the development of new electrochemical storage and conversion technologies, as well as fast and contactless control or diagnosis of ionic conduction in polycrystalline solids.