Thermally Conductive, Electrical Insulating, Optically Transparent Bi-Layer Nanopaper.

Cellulose nanofiber (CNF) from abundant and renewable wood is an emerging material with excellent mechanical, chemical, and optical properties. Transparent nanopaper made of CNF (CNF-nanopaper) could potentially replace plastics in electronics due to its excellent optical transparency, mechanical strength, and biodegradability. However, CNF-nanopaper normally has a low thermal conductivity and poor stability in increasing temperatures, which is not suitable for long-term stability and reliability in devices. Herein, for the first time, we report a thermally conductive, electrically insulating, and optically transparent nanopaper using a bilayer design where a thin layer of boron nitride (BN) nanosheets were coated on the CNF-nanopaper. An optical transparency (70%) and a thermal conductivity (0.76 W/m/K) were successfully achieved through a solution-based process at room temperature. Such an optically transparent, electrically insulating, and thermally conductive bilayer nanopaper can find applications in a range of electronic devices.