▎ 摘　　要

The scaling-down of chip size and the increase in on-chip power density require highly efficient thermal management materials in electronic packaging. The excellent thermal conductivity and unique two-dimensional structure of graphene make it an ideal candidate for heat spreader films to alleviate the hot spots on chips. Reduction of graphene oxide (GO) films has been utilized as an effective way to achieve the large-scale production of the thermally conductive graphene films. However, this approach usually requires high-temperature annealing at 1000-3000 degrees C in order to achieve the high conductivity needed, which dramatically increases the energy and time consumption and thus the total cost. In this contribution, graphene films free of high-temperature treatment with an in-plane thermal conductivity up to 1102.62 W.m(-1).K-1 are obtained by simple chemical reduction of GO. The high conductivity is achieved by adjusting the concentration of GO solution and mixing GO sheets with different sizes to optimize the connectivity and compactness of GO films. While the majority of previous work relies on the graphitic structure restoration by high-temperature treatment, our work demonstrates that the geometric organization of graphene sheets also plays an important role in the thermal conductivity of graphene films.