Rational Design of Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXene Inks for Conductive, Transparent Films.

Guo, Tiezhu; Zhou, Di; Deng, Shungui; Jafarpour, Mohammad; Avaro, Jonathan; Neels, Antonia; Heier, Jakob; Zhang, Chuanfang · ACS Nano · 2023

basic_science · Level V

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Abstract

Transparent conductive electrodes (TCEs) with a high figure of merit (FOM<sub>e</sub>, defined as the ratio of transmittance to sheet resistance) are crucial for transparent electronic devices, such as touch screens, micro-supercapacitors, and transparent antennas. Two-dimensional (2D) titanium carbide (Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>), known as MXene, possesses metallic conductivity and a hydrophilic surface, suggesting dispersion stability of MXenes in aqueous media allowing the fabrication of MXene-based TCEs by solution processing. However, achieving high FOM<sub>e</sub> MXene TCEs has been hindered mainly due to the low intrinsic conductivity caused by percolation problems. Here, we have managed to resolve these problems by (1) using large-sized Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> flakes (∼12.2 μm) to reduce interflake resistance and (2) constructing compact microstructures by blade coating. Consequently, excellent optoelectronic properties have been achieved in the blade-coated Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> films, <i>i</i>.<i>e</i>., a DC conductivity of 19 325 S cm<sup>-1</sup> at transmittances of 83.4% (≈6.7 nm) was obtained. We also demonstrate the applications of Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> TCEs in transparent Joule heaters and the field of supercapacitors, showing an outstanding Joule heating effect and high rate response, respectively, suggesting enormous potential applications in flexible, transparent electronic devices.