▎ 摘　　要

In 5G era, high frequency and high speed transmission of data will generate much heat in electronic and optoelectronic devices. Thermal management materials with high thermal conductivity (K) and thickness are required for spreading the heat generated locally in such devices. Conventional thermal management materials mainly include metallic materials and non-metallic carbon-based materials. In general, metallic materials can be processed with high thickness but have limited K, while non-metallic carbonbased materials with high K are difficult to obtain high thickness. To solve the conflict between high K and high thickness, we propose a feasible way to fabricate ultrathick graphene films with high K based on the self-fusion character between graphene oxide sheets. The achieved ultrathick graphene film has high thickness up to 200 mm while retaining a high K of 1224 +/- 110 W m-1 K-1. Furthermore, the ultrathick graphene film is proved to render high heat flux during the heat transfer process. Our work provides a solution for the heat dissipation of high frequency and high power devices. (C) 2020 Elsevier Ltd. All rights reserved.