Rational Design of Ti 3 C 2 T x MXene Inks for Conductive, Transparent Films.

Transparent conductive electrodes (TCEs) with a high figure of merit (FOM e , 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 3 C 2 T x ), 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 e 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 3 C 2 T x 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 3 C 2 T x films, i . e ., a DC conductivity of 19 325 S cm -1 at transmittances of 83.4% (≈6.7 nm) was obtained. We also demonstrate the applications of Ti 3 C 2 T x 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.