Facile and time-resolved chemical growth of nanoporous CaxCoO2 thin films for flexible and thermoelectric applications

TL;DR

This paper introduces a simple, fast, water-based chemical method for growing nanoporous Ca0.35CoO2 thin films on flexible substrates, promising for thermoelectric applications from wearable devices to energy harvesting.

Contribution

It presents a novel, ligand-free, time-resolved chemical process for fabricating nanoporous Ca0.35CoO2 films on flexible substrates, suitable for scalable industrial production.

Findings

Films are flexible and can sustain bending with a radius of 15 mm.

Power factor reaches 0.50 x 10^-4 W/mK^2 near room temperature.

Method is simple, fast, and potentially cost-effective for industrial scaling.

Abstract

CaxCoO2 thin films can be promising for widespread flexible thermoelectric applications in a wide temperature range from room-temperature self-powered wearable applications (by harvesting power from body heat) to energy harvesting from hot surfaces (e.g., hot pipes) if a cost-effective and facile growth technique is developed. Here, we demonstrate a time resolved, facile and ligand-free soft chemical method for the growth of nanoporous Ca0.35CoO2 thin films on sapphire and mica substrates from a water-based precursor ink, composed of in-situ prepared Ca2+-DMF and Co2+-DMF complexes. Mica serves as flexible substrate as well as sacrificial layer for film transfer. The grown films are oriented and can sustain bending stress until a bending radius of 15 mm. Despite the presence of nanopores, the power factor of Ca0.35CoO2 film is found to be as high as 0.50 x 10-4 Wm-1K-2 near room temperature. The present technique, being simple and fast to be potentially suitable for cost-effective industrial upscaling.