Thermoelectric Performance and Morphological Stability of Thin Titania: Carbon Black Hybrid Films Against Humidity and Light Irradiation

Thermoelectric titania thin films are of interest for energy generation and sensor applications. To be usable in practice, they need to be stable against atmospheric conditions. Nanostructured titania:carbon black hybrid thin films are investigated for their stability against increased relative humidity and light irradiation. These thin films are created using water‐based, environmentally friendly production and further emphasize scalability by using slot‐die coating as a deposition technique. The thermoelectric performance during operation is correlated with morphological changes, by simultaneously measuring operando grazing incidence small‐angle X‐ray scattering and Seebeck coefficient. The thin films are stable against light degradation. There are neither morphological changes nor changes in the Seebeck coefficient during five hours of operation. However, they show a significant decrease in performance due to elevated moisture. This humidity degradation is also visible in the morphology of the samples and corresponds well with decreases in the Seebeck coefficient. Using the ionic liquid 1‐ethyl‐3‐methylimidazolium dicyanamide post‐treatment is found to both increase the Seebeck coefficient and the stability against elevated relative humidities. Therefore, the moisture sensitivity of titania:carbon black thin hybrid films can be overcome with such a simple treatment, which renders our approach a promising first step toward sustainable thermoelectric thin films.